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My Ratsun Datsun 521, now with L-20-B and a five speed

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The 520 with the J13 was rated at one ton. I can't find any difference between 520 and 521 rear springs so assume the half ton rating is just paperwork numbers. I had 700 pounds on my 521 and it rode just like a car. The 700 pounds made the springs flex on bumps and it was quite comfortable.

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I’ve had the same result. Truck rides great with weight in the back. I made a Home Depot run this spring and had a bunch of top soil/compost in the back and the ride was better than empty.

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I have been working on cleaning up the rust, and old paint in the bed of Ratsun.  It is a long process, I have been doing smaller areas, and getting primer on the areas, before working another area.   I am still figuring out what methods I can use with the tools I have.  The following six  pictures are the areas I cleaned, then used a wash primer on ,  then an epoxy primer on.












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Ratsun bed rust removal more info.  In the previous post, i was still trying different methods of removing rust, and old paint and primer.   I cleaned the areas pictured in the post above with a 3M clean and strip disk, in a air sander. 

Amazon link for the disks:


These disks are not cheap, but they work really well for removing rust, old paint, and not removing too much good metal.   Because of the price of the disks, I tried a few other methods of cleaning the bed prior to paint.


This is some stuff I wore in some of the cleaning.  I have prescription glasses, they are "safety" glasses, I wear then all the time just to correct my vision.  In this picture, I am also using a dust mask, and a face shield.  

As old as our Datsuns are, there is a good possibility that paints and primers used on them from the factory, and in any body work since then contain lead.  

Not so much with the strip disk and grinder above, remember I always are wearing safety glasses, the face shield is not a necessary item.  But with the next tool it definitely is.



This is a wire wheel with a 5/8 hole in it, on my 9 inch Metabo angle grinder.  The wire wheel is rated for the RPM the grinder turns, 8950 I think.   The grinder is rated for a power consumption of 2,400 Watts.  I can pop a 20 amp breaker by loading this grinder heavy, the grinder is a beast.

A face shield and safety glasses is an absolute must with this tool. 

However, the areas on the bed ridges below the grinder were cleaned up with this grinder and wheel, fairly quickly.   I used a lot of down pressure on the wire wheel, It was easy to hold it in the bottom of the grooves, more difficult on the top of the grooves. 



I used a conventional flap disk on the top of the grooves.




After the 9 inch angle grinder, and flap disk, I went over the areas again with a clean and strip disk.

No picture, not a lot of difference in the camera, but the metal does look cleaner to the eye, in good light.

The next thing I did was apply a phosphoric acid solution the the areas of the bed I had cleaned.  This picture is after the phosphoric acid dried.


The metal can stay with the phosphoric acid on it for a short time.  If it gets wet, the phosphoric acid will start to dissolve rust again.  But this is not a long term, over the winter solution.


I cleaned the dried phosphoric acid off the bed with a  3M clean and strip disk, I also used a Nylox brush in a drill.  These brushes are available at Ace Hardware stores.


This brush works really good for a final cleaning of metal getting ready for primer, but is is kind of slow.  if you use too much pressure with it, or too much speed, the nylon in the brush will melt, and stick to the metal, but at a lower speed, it really cleans the metal well, leaving very little residue on the bare metal.


Right after using the Nylox brush, I sprayed the 1791/1792 wash primer.  Instructions with the wash primer say to spray within a half hour of cleaning the metal.  Then Epoxy primer within a day of spraying the wash primer.  Dry time on the wash primer,  about 10 minutes.

See pictures in the above post, if you want.

I sprayed these areas with grey epoxy primer, then a second coat of white epoxy primer,


And then paint, PPG Omni MTK single stage, (no clear coat) paint.




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Brake problems again.  The brake pedal started to sink again on my way down a hill, close to my house.  I turned around, and carefully came back home.  This time, the brake master cylinder was empty when I got home.  I looked for a fluid leak at each wheel, no leaks.  Then I put some fluid in the master cylinder, and pumped the brakes some more.   Brake fluid was leaking on the floor of the garage under the gas tank filler.  A closer look at the brake line had a lot of rust on the outside of the brake line below the fuel filler hose, and a lot of dirt and crud on the frame rail there.

It also became apparent that I am going to have to remove the gas tank to remove and replace the rear metal brake line.

I had the gas tank out of Ratsun when I got it running, in 2013, and I put grease on the bolts holding the gas tank under the bed of the truck.  The bolts came out pretty easily, without destroying threads, or breaking bolts.

I then removed the rear brake line, there was several places that metal tabs just bent over the brake line, and of course the flare nuts under the cab, and at the rear, above the rear axle.

Rear brake line flare nut union, under cab, by right side frame rail



In this picture, I had already started to bend the new brake line.  This is near the left frame rail, above the rear axle.



Sorry, no pictures of removing the old rear brake line.  I tried to do as little bending of the old brake line as possible so I could copy the bends when I got new brake line.

I do not have a good high quality brake line flaring tool. and have had poor luck making double flares in brake lines.  

I measured the old brake line by using a tape measure, and trying to follow each bend and contour of the old line, and measured 8 feet, or 96 inches.  The auto parts store did not have 8 foot brake lines, and the closest they could come to 8 feet is a 40 inch line, and a 60 inch line, and union to connect the two lines together, making about a 101 inch brake line.


This is a picture of a brake line bending tool I have.  I am comparing the bends I am putting put in the new brake line to the old brake line.   After a few bends, I test fitted the new brake line, and did more bends.



Close view of the brake line bender. 



Comparing bends in the new line to the old line.



More comparing of brake lines.



This is the same picture above, but is test fitting the rear part of the new brake line.  I used the 40 inch section here.  The brake line is held in a clip on the bed mounting bracket, and there is a bend holding the brake line away from the front edge of the bed mounting bracket.



The brake line then goes over to the top of the frame rail, under the fuel tank filler hose.



Forward of the fuel filler hose, the brake line goes back down on the inside of the left frame rail.



This is also a duplicate of a picture above.  The brake line goes through the grommeted hole, and then has a 90 degree bend to follow the frame cross member.



One method I used the get the new brake line to match the old one, is to use some wire to hold the old and new lines together, and bend to match.



Farther along the bends of the brake line.



Even farther along the brake line.



The new brake line was put through the grommeted hole,



This is the new brake line as it crosses above the cross member, above the hand brake cable, and below the drive line.



Remember, the old brake line was 96 inches long, and I bought a 60 inch and a 40 inch piece of brake line, this is how I dealt with the extra length of the brake line.



Finally, the front part of the new brake line matched the rear part of the new brake line and I screwed the coupler together. and tightened the brake line fittings, and bled the brakes.



That was about a week ago.  I have been driving Ratsun and the brakes are working good.

Edited by DanielC
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Winter is getting close, and I have done some stuff to Ratsun to help it run better when it is cold.   The 1974 620 air cleaner I cleaned and repainted got put on the carburetor,



I repaired the heat stove that fits over the L-20-B exhaust manifold, and installed the duct that takes hot air off the exhaust manifold, and goes to the air cleaner snorkel.  This thin sheet metal was pretty rusted out, the bolt holes were oversized, and I made a new piece of pipe to attach the hot air duct to.  I cut some small piece of sheet metal to cover the oversized bolt holes in the this sheet metal.  Then I spot welded from the inside of the sheet metal the pieces to the sheet metal.  I did not have the correct size of pipe to attach the duct, but I had a piece of pipe from exhaust pipe work that was slightly oversize.  I made a few lengthwise cuts in that piece, and then welded the gaps together, and that made the diameter of the pie smaller.  I then was able to weld from the inside the new piece of pipe to the thin sheet metal.



I need the correct bracket that holds the front of the air cleaner to the intake manifold.



I put the L-20-B engine in Ratsun June 18th, 2018.  This is the first time I put a L-20-B engine in a 521, and I was concerned about possible overheating problems with the stock 521 radiator.  Long story short, I used a 7 blade fan off a 1980 720 truck, with a L-20-B engine, no air conditioning.  This fan.7BBladeFan.JPG


This is a picture of that fan, fitting inside the fan shroud of a stock 521/L-16 radiator and fan shroud.  This fan is off a 1980 720, L-20-B non AC truck.



This is a four blade fan, It cam out of a 1974 620 truck.  I put the four blade fan on the L-20-B engine in Ratsun.  Remember, I put the L-20-B in Ratsun in June, and it is now December.  I drove Ratsun a lot since I put the L-20-B, even through the heat of the summer of 2018, without a hint of overheating.  In fact, the temperature gauge in Ratsun would consistently read below the mid point line in the stock temp gauge.  If the mid point line is 1/2, the gauge was reading between 3/8, and 7/16.



I got a little ahead of myself.   To get to the fan, I needed to drain and pull the radiator.

First, I got this drain pan to catch the coolant in.  Notice also the old oil bottle with the side cut out of it.  The radiator drain on a 521 is above the front frame cross member, and when the coolant is drained out of the radiator, it runs on the cross member, and makes a mess.



My finger is on the radiator drain petcock.



This is the cut oil bottle, in place to catch the coolant coming out of the radiator, and draining the coolant into the drain pan, without running all over the parts of the frame, making a mess.OilBottleFunnel.JPG


The drain pan under the truck.DrainPan2.JPG


In this picture, the four blade fan is installed on the engine, and three of the four lock tabs are bent over the bolts.



To put the lock strips in over the bolt head, I turn the bolt until a flat side of the bolt is parallel with the end of the lock strip.  Then I use the edge of a cold chisel to bend the lock strip close to the bolt head, gently.



Then I use an aluminium punch to bend the lock strip more, again gently.



and finally tap the end of the lock strip over the bolt head.  I know the fan is on backwards.  Remember, I am having no cooling problems with this truck.



Here I am lowering the radiator into place. The radiator fits with the fan shroud on the radiator.  Hold the radiator against the core support, and if needed, gently bend a fan blade toward the engine.



Just a picture of the radiator bolts on one side, being put in.  you can hold the radiator with one hand, like the picture above. and move the radiator around to get one bolt started.   Once one bolt is started, you can pivot  the radiator on that bolt, and get a second bolt started on the other side of the radiator.  Do not tighten either of those two bolts yet.  Go across the radiator, start the third bolt, and across the radiator again, and start the fourth bolt.  Tighten the four bolts finger tight, then use a socket, extension and ratchet to tighten the four radiator mounting bolts.



Finally, I changed the thermostat.  I was just using the thermostat that was in the L-20-B engine when I got the engine from the junkyard.  The old thermostat was a 180 degree thermostat, this new thermostat is a 195 degree thermostat.195Tstat.JPG


I also got a new thermostat gasket, TstatGasket.JPG


I cleaned both surfaces on the thermostat cover, and housing, by first carefully using a sharp knife to remove old gasket without gouging the cover,or housing surface, then gently using a 3M bristle brush, TStatCoverClean.JPG


Then I used a flat file on the gasket surfaces.



Because bolts in aluminium tend to seize, and rip out treads, I use some grease on the thermostat cover bolts, this grease from a Mercury outboard marine dealer.  Because you greased the bolts, you need to not tighten the bolts as you would a dry bolt BoltGrease.JPG


Finally, I put a paint filter funnel in a plastic funnel and poured the coolant back into the radiator.  


This is the crud in the filter funnel. 



I took Ratsun for a short test drive after the work was done.  The drive was short, no freeway, or hills, but the temperature gauge finally went to the mid line on the temp gauge.   Tomorrow, I will check the radiator coolant level,

Edited by DanielC
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If you have a granite counter top or some other nice flat surface, I like grinding sealing surfaces flat with some 400 then 800 sandpaper. 

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Sheet of glass from an old stereo cabinet and some 80 sandpaper followed by 150.... Use 80 if you want the job finished in a morning. The 150 barely does anything but dull the finish. This U67 has a high spot. It shows results very fast at first but really slows down as you get close.




The thermostat housing wasn't great with broken TVV and by pass fitting rusty so I had a '79 laying around....




YES I also used anti-seize on the bolts, and teflon tape on the by-pass fitting

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The coolant level seems to be holding in the radiator.  The engine warms up faster, and it is running with the temp gauge at the half way line.  The four blade fan is much quieter than the seven blade fan was.

On Tuesday, I need to get a ton of wood pellets for my pellet stove.  That involves a few miles of freeway driving.

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I got a chance to do some free way driving, yesterday.  I am really liking the fact that the four blade fan is much quieter than the seven blade fan I had on the engine.  Also yesterday, I filled the tank on Ratsun, and that last tank averaged a little over 23 MPG.  this is with very little freeway driving, mostly short trips, and about weekly, getting a load of hay.  The temp gauge on Ratsun goes up to the mid line on the stock gauge, and no farther.

Today, I went to Coastal Farm, and got a ton of wood pellets in Ratsun.  This is that load of wood pellets right before I unloaded them.


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Hey Daniel


Can't believe how well the old Datsun took all that weight. That is amazing. I think the ole truck likes getting loaded right up to the edge too.



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I am getting ready to put the 1980 720 five speed transmission i got last about a year ago, with the L-20-B engine that is already in Ratsun.  But I have been working on some other Datsun stuff in the garage, and my garage is pretty crowded.


This 521 frame and engine are Dragon Two, another one of my 521 trucks.  It is a little too cold to paint, so I am doing mechanical stuff.  But I am using this truck to fabricate transmission mounts, and get measurements on drive line shortening for the longer five speed transmission.



This is the cab of Dragon Two.



And this is the front end of Ratsun up on ramps, so I can work under it.  what you  do not see is that I have to put some stuff in the garage in the bed of Ratsun just so I can get Ratsun that far into the garage, to work on it and I still cannot close the garage door.



Most five speed L series transmissions are longer than the 521 four speed transmission.  That requires some changes to the bracket that holds the transmission mount.  I neede to get this mount out of the way for some checking of fit.  But first, there is a lot of crud on the cross member, and bracket.



A work light so I can see under the truck.  This is an old fashioned halogen light, in January, I like the warmth of it.



Things under the truck are dirty enough to wear these.



finally, and old putty knife to scrape crud off the cross member, and trans bracket.  The sheet of plastic is to catch the crud, and not make as much of a mess on the floor of the garage.



Some of the crud off the frame cross member.



The cross member, after scraping



Then I removed the bracket.  First, there are two 5/16 bolts that go forward through the transmission mount, and the bracket. Remove the two nuts, and lock washers, 1/2, inch wrench, and then the bolt.  I had to gently drive the bolt out with a 1/4 punch.  Then, you can gently lift the back of the engine with a block of wood on the oil pan, and a jack.  The transmission mount should slide up and off the bracket.  with the transmission lifted, you can remove the four 3/8 bolts holding the bracket to the frame cross member with a 9/16 wrench.  Finally, remove the transmission mount from the transmission with a 14 MM or a 17 MM wrench or socket.  521 body parts are inches, engine, transmission and differential carrier are Metric.



I cheated, and got a transmission mount and bracket that I had previously cleaned.




But before I put the clean bracket and transmission mount on, I wanted to to a test fit of a piece of steel I am going to make a new mount for the five speed transmission.



Then i reinstalled the bracket, and transmission mount.  I need to do some work on the transmission.




Edited by DanielC
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521 5 Speed Transmission Mount Mod





















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Nice transmission bracket!   However, I want to keep the stock 521 four speed mount in case I ever want or need to put the stock four speed transmission back in any of my 521 trucks.  i am also going to use the rubber transmission mount that came on the 1980 720 I got the engine and transmission from.


It is a good idea to replace the rear seal on the five speed transmission, and I want to do that.  There has also been mention of checking the tightness of the nuts inside the transmission on the main shaft, and the reverse idler shaft.  Yesterday, I took the tailshaft housing off of the 720 transmission.

First, I remove the bolts holding the tail shaft housing on the transmission.  12 MM head, M8-1.25 bolts.   I did not remove any other parts off the tail shaft housing, In hindsight, I should have.



In this picture, there is a large nut just below the shift coupler, and a pin below that on the top of the transmission.  Remove the large nut, there is a spring and a detent piston under the nut.  Remove the pin on the top of the transmission, it has a clip on the other side.  The detent piston and pin limit the movement of the shifter.  There is also a cast bracket on the side of the transmission below the shift lever coupler.  This cast bracket prevents the tail shaft of the five speed from slipping up into the cab of a 521, when you are installing the five speed transmission, with the engine still in the truck.  I just cut it off close to the transmission with a hacksaw.



This diamond shape with the two bolts holds a mechanism that prevents a direct shift from fifth gear to reverse.  Before removing it, mark what end is toward the front of the transmission.  Then remove it. 5spReverseBlocker.JPG


Remove the speedometer pinion holder, the object on the left of the picture.  You can also see the clip that hold the pin that is at the top of the transmission, two pictures above.   Taking all that stuff off the tail shaft housing allows the main shift rod and finger that goes into the shift rod gate more freedom of movement, to allow the tail shaft housing to be removed from the transmission.



There is this tab on the bottom side of the tail shaft housing, just above the block of wood in the picture.



There is this tab on the top side of the tail shaft housing, just above the block of wood in the picture.  I hit the block of wood with a hammer, alternating the top, and bottom tab of the transmission.



It took a lot of messing around to remove the tail shaft housing from the transmission.  I was preoccupied with that, so no pictures for a while.  I did eventually get the housing off the transmission.  honestly, i cannot remember if I had to remove some of the stuff off the tail shaft housing that limits the movement of the shift rod.  I did have the reverse blocker, and a pin that goes through the tail shaft housing to get the housing back on the transmission, with the shifter working.


With the housing off, I could feel the nuts on the main shaft, and idler shaft were both loose.

How do you tighten a nut on a shaft in a transmission when the shaft turns easily?  Put the transmission into two gears at once.

The three rods in the foreground of the picture are from left to right the reverse/fifth shift rod, the third/fourth shift rod, and the first and second shift rod.  The transmission has an interlock that will not allow two adjacent rods to go into gear.  But you can move shift rods NOT adjacent to each other.  In this picture the transmission is in reverse, and second gear at the same time.  Any combination of fifth, reverse, and first or second will work. 



That locks the transmission shafts from turning, but now you need to hold the case of the transmission.  I just clamped the bell housing to the table I was working on.



The other side of the transmission.


Like I said, the two shaft nuts were loose.  This picture is after I had tightened the main shaft nut.  Not shown, I used a 1/8 punch, with a chisel point ground to unstake the two nuts.



The reverse Idler nut, after tightening.



I had a wrench that fit the reverse idler nut, a 1 1/16 open end wrench.



for the main shaft nut, I used a big Cresent WrenchMainshaftCresentWrench.JPG

I will add some more to this post in the morning, I am tired.

After tightening the nuts on the main shaft, and reverse idler, I used a centerpunch to restake the nuts.



Main shaft nut staked.


Reverse idler nut staked.



I have a small slide hammer, and used this to hook under the rear seal and pull the seal out of the transmission.



I have taken stock 521 four speed transmissions apart before and I had some of the gaskets and seals from working on those transmissions.  I found a seal that looked like the old five speed seal in my four speed transmission parts.  I used a  block of wood to drive a new seal in the tail shaft housing.  I used a lot gentle taps, and after every few taps with a hammer, looked at the seal and then biased the hammer toward the high side of the seal going into the transmission.


New seal, installed.



There is a lot of work missing in getting the tail shaft housing back on the transmission.  If I did not remove the reverse blocker, when I removed the tail shaft housing, I did remove it before putting the transmission back together. 

The reverse blocker is a mechanism mounted on a diamond shaped plate, held to the transmission with two M6-1.0 bolts,t hat have 10 MM heads, and a pin that through the top of the tail shaft housing just forward of the shift lever.   I also removed the speedometer pinion.   There is also a detent and a spring behind a larger nut that goes into the side of the tail shaft housing I removed.


The basic process to put the tail shaft housing is this.  Turn the shift lever coupler counterclockwise until the finger inside the transmission hits the top of the housing, and lower the housing over the back of the transmission.  As some point, a second smaller finger will hit the gears on the main shaft, and you will have to rotate the shift lever coupler clockwise little to clear that obstruction. This will allow the tail shaft housing to continue down.  Do not let it go all the way down.   Now rotate the shift lever coupler more clockwise, and feel for the finger on the main shift rod in the tail shaft housing to enter the space between the 1/2, 3/4, and 5/reverse shift rods.  The shift lever coupler should be straight to the tail shaft housing when this happens.   When it felt like the tail shaft shift rod finger was in  the proper place,  I put the pin, reverse blocker, and shift rod detent back in the tail shaft,

and then put two bolts back in the tail shaft housing, one on each side.  Then I put the gear shift lever back on the transmission, and checked if the transmission will shift into all the gears normally.  After that we get to this picture.  I removed the two tail shaft housing bolts, and used a block of wood to slightly lift the tail shaft housing off the transmission.  Then I squirted some gasket goo into the gap between the tailshaft housing, and transmission.



This is the gasket goo I used.



This is the excess goo squished out after the tail shaft housing was allowed to move back down.  It was wiped off, and a little more goo squished out when the tail shaft housing bolts were tightened.



Of the four switches in this picture, which one is the reverse light switch?


Edited by DanielC
correct a missused word, added some pictures
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About 10:45 Pm Pacific Standard time, Wednesday January 9th, 2019, I took Ratsun for a short test drive with a five speed transmission installed in it.

I still need a speedometer pinion, a longer speedometer cable and to hook up the reverse light switch.

Tomorrow is a drive to work.


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Reverse is the far right just behind the clutch arm dust boot.


I had the same style 4 speed in my 710 and put my '79 zx 5 speed in. By removing the speedometer cable from the clips on the under side of the body I pulled it up into the engine compartment then fed it down behind the head over top of the transmission and diagonally to the passenger side. There was enough slack to connect it to the speedometer pinion and it's been on and working fine for years. I imagine the 521 is the same.


Back in the late '70s I put a car L20B in my 521. It had a great amount of pull in 3rd and 4th than the L16. I really like it.  

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On 1/7/2019 at 12:05 AM, DanielC said:

  I used a lot genital taps,


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I like that Ratsun allows you to correct or edit your post without a time limit.   And at least I know some are reading my posts.

I drove Ratsun today, to work and back, a round trip of slightly less than 8 miles.  I got a vibration I suspect is a drive shaft imbalance.  Another one of my 521 trucks also has a long tail five speed, and I think by putting the rear tires up on some ramps, I can limit the amount of gear oil that leaks out of the transmission when the tail shaft is pulled out. 

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What speedometer pinion do you need Daniel.

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Charlie, Oh, wow!  Thank you.  I think I need a 21 tooth purple speedometer pinion, I have a 4.375 rear axle ratio.


This is Dragon, another one of my 521 trucks,  it runs, drives, but needs doors, fenders, and a hood to be painted when it is warmer, and some other body work.  But it has a five speed transmission I put in it in the late 1970's.   I put it up on these ramps, and then removed the drive line from it.  With the rear end of the truck on these ramps, no gear lube came out of the transmission when I pulled the slip yoke out of the transmission.   To remove the drive line, with a slip yoke for a five speed is a lot easier than on a stock 521, with a bolt flange on the four speed transmission.   You unbolt the four bolts at the differential, 1/2 inch open end wrench, and remove the two bolts that hold the carrier bearing bracket in the middle of the drive line.  Then you push the rear half of the drive line toward the carrier bearing, and the aft end of the drive line come off the differential.  Remove the carrier bearing bracket, and then slip the whole drive line to the rear, and out of the truck.

With a stock four speed you have to remove the bench seat, and the plate that covers the shift lever coupler.   Then you can loosen one drive line bolt from inside the cab.  You then have to rotate the drive line a 1/4 turn, and remove the next bolt, and repeat that step two more times.  But on the other hand, you do not have to worry about oil leaking out of the rear flange on the stock four speed transmission 



This is not my Dragon thread, this is my Ratsun thread.   if you are new to my posts, I named some of my 521 trucks.


Anyway, I pulled the drive line I had just had shortened out of Ratsun, using ramps just like with Dragon. and put Dragon's five speed drive line in Ratsun, and took it for a test drive.  I lot less vibration.


By the way, I am adding more pictures to a post above, about transmission work to get the five speed installed in Ratsun.





Edited by DanielC
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Daniel what size tires are you using? This will give the diameter and with the differential gear known, the speedometer pinion can be selected.


The stock 521 and tire uses a 19 tooth gear.

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Hey Mike, thanks for jumping in.  My rear tires are  205 70R14.  This tire size is pretty close to the stock diameter of the 6.00-14 OEM 521 tire.

The L-20-B engine and 5 speed transmission came out of a 1980 720 pickup, with AC.  I tried to find the rear axle ration on the body tag on that truck, but I could not find where the ratio was on the truck.  I do have the speedometer pinion that came with the 1980 720 engine and transmission.   The speedometer pinion is currently in Dragon.

I should pull the pinion out of Dragon, put it in Ratsun, and check the mileage to and from work, or another known distance.


More information on the transmission install.  

This is how i made the transmission mount.  I started with a piece of 3 inch by 1 1/2 inch 1/8 thick rectangular tube.  I had already cut part of it away, so that a 72 transmission mount would sit inside it.  I just needed to cut this piece to fit in between the bracket I had already made to fit on the 521 frame cross member.  I am using a scrap piece of steel to help guide a square cut on that piece of steel.



This is how I set up the scrap steel to guide the cut.  First, I used the big "C" clamp to hold the scrap steel on the part I want to cut.  then I put the two clamps on the side.  Then I removed the center "C" clamp, so I could have room for the angle grinder.



After removing the middle "C" clamp, I checked for squareness.



Using the scrap steel to guide the cut with a cutoff blade, in an angle grinder.



These are the two pieces for the transmission mount bracket. 



This is the 1980 720 transmission mount, upside down.  Note, the two threaded holes are M10-1.25.  Every other M10 bolt I have ran into on Datsuns are M10-1.5.



This is how the transmission mount parts fit together.  They are not welded together, yet.



At this point, I needed to put the five speed transmission into the truck.  that was difficult.  Monday evening, late, I discovered an unused boss cast into the transmission tail shaft housing that would stop the tail shaft housing from going up into the cab of the truck.  Tuesday morning, I cut the boss off the transmission with a hack saw.  Then the tail shaft housing went into the cab of the truck to allow the transmission to fit in , almost.   When I lifted the front of the transmission, the bell housing hit the pressure plate of the clutch.  I then took the pressure plate, and clutch disk off the flywheel.  Then the transmission went up to where it could slip aft far enough to just barely get the clutch disk, and pressure plate back on the flywheel, with a clutch disk alignment tool.  When you ate lifting the transmission into place,  the starter bulge on the side of the transmission makes the transmission wide enough to sit on the torsion bars of the 521, if you need to rest before sliding the transmission into the engine.

I use pair of longer M10-1.5 bolts to help guide the transmission onto place.  This is the guide bolt installed by the starter.



This is the guide bolt on the left side of the engine.   After a bit of work trying to put the transmission completely on the engine, and after I had some lunch, the transmission slipped in.  Then put the four engine to transmission bolts in.



With the engine and transmission bolted together, I bolted the frame part of the transmission mount bracket to the trucks frame.  I then bolted the transmission rubber mount to the transmission, and the cut piece of 3 x 1/2 rectangular tube to the transmission mount.  I jacked up the transmission and engine to where I wanted the bracket to hold the height of the rear of the transmission, and tack welded the two mount pieced together.   The battery cable hanging down is how I grounded the MIG wire feed welder



The tack welded bracket was removed, and the welds were completed on the bracket.



Just another picture of the transmission mount bracket.



This is the welded mount installed in the truck, holding the transmission.



And then I put everything back together.




Edited by DanielC
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The difference between those two tires is 0.25% or 1/2 MPH at 50 MPH so a 19 tooth is good enough. Each tooth difference is 5% to 6% change.



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