74 620 trans

[jwerty1]

what would be the best trans to swap in a stock 74 620. L18 and 4 speed. I'm looking to get a 5 speed, with the least mods as possible. Also, the carb needs work and/or upgraded. Wondering what the best and lowest mod option would be. I'm not against excessive mods, just want stuff that could work without the truck being down for a couple weeks. I use it pretty much daily, I am the 2nd owner and it has 60k miles. It's a really good truck for the age and being east coast.

[Jayden71]

 

There is lots of usefull info here on this forum noob. Just look around in the drivetrain section. There is numerous threads on 5 speed swaps. Take a little time and do some research and your stay here at Ratsun will be a pleasant one :D

[datzenmike]

 

 

:lol: :lol:

 

The FS5W71B 5 speed was an option starting in '77 and up on the 620 and the 280x and zx cars and starting in '79 on the Maxima. It was also an option on the (one year only) 1980 720 2wd. All were L series equipped and so it will fit your '74 with zero mods. The '79 620 and the '80 720 were 'wide ratio' gear sets, the '81-'83 280zx were a 'close ratio' gear set. All other years were equipped a 'mid ratio' gear set. A wide ratio tranny favors a truck that carries heavy loads or a camper and has a very low high revving first gear. A close ratio tranny favors a light duty truck and good highway mileage. A mid ratio is somewhere in between. (this is a very generalized description)

 

Which ever you choose keep and use the release bearing collar (the thing that holds your release bearing) that is on your truck now and not the one that may come with the 5 speed. Your collar is matched to your clutch size so keep it. By all means replace the bearing with a new one.

 

Can you tell a 5 speed from a 4 speed by looking at it???

[yello620]

:lol: :lol:

 

The FS5W71B 5 speed was an option starting in '77 and up on the 620 and the 280x and zx cars and starting in '79 on the Maxima. It was also an option on the (one year only) 1980 720 2wd. All were L series equipped and so it will fit your '74 with zero mods.

 

Early production 1974 model truck still had the short tail 4 speeds. If you have a short tail truck, then you need a few more parts, but still a super easy swap. Does you 4 speed have removable pan/plate on the bottom of it?

[yello620]

Good point about the '74 but he said L18 motor and the 'new' F4W71B came out only with the 'new' L18 when it replaced the 'old' L16. Only the L16s had the short tranny.

My first truck was a 74 620 with an L18 an a short tail tranny. Purchased the truck in completely stock condition in 1987. Production stamp on the door was early 74 too, just dont remember which month. There was no 73 markings on the door tag.

[datzenmike]

Good point about the '74 model year however he did say he had an L18. The L18 was introduced in October '73 along with the 'new' F4W71B 4 speed. Prior to this date only the L16 was equipped with the 'old' short F4W63 4 speed.

 

* sorry had to edit this info.

 

 

July '73 would be the start of the '74 model year, give or take. It's slightly possible that a few short tranny/L18 were produced during this change over in Sept/Oct. It's more likely that between '73 and '87 someone kept it on the road by swapping the tranny and driveshaft in? If done properly, I would agree, you couldn't tell it from stock.

[jwerty1]

Thank you for the replies, its been a while. My truck started making a knocking noise down low at idle. Ripped it out, found it was the flywheel bolts came loose. Slapped it back together with some new gaskets, oil pump, repaired floor pan, new carb. Now my clutch just started slipping with a new clutch disc. So I'm finally back in the market for a trans upgrade. No I do not know how to tell a 4 sp from a 5 sp just by looking at it.

[Rays74]

Me neather, J........I just look for the shifter to slip into the notch above reverse in any trans I might be thinking could be a 5 gear.....too simple? Yep, I might be :D

 

--Ray

[ggzilla]

July '73 would be the start of the '74 model year, give or take

Why's that? The 'traditional' model year starts in October. And many years Datsuns changed in October too.

 

The 1974 factory service manual only lists the L18.

[ggzilla]

Yes, you can put the shifter over and up, but then you should verify by seeing if the output shaft rotate slower than the input.

 

I can't count the number of times guys bought a 4-speed after shifting into "5th". Can't go by that alone.

 

One ID feature is to look at the bottom of the transmission. If the gearbox has "pan" then it's not a 5-speed.

[Rays74]

Yes, you can put the shifter over and up, but then you should verify by seeing if the output shaft rotate slower than the input.

 

I can't count the number of times guys bought a 4-speed after shifting into "5th". Can't go by that alone.

 

One ID feature is to look at the bottom of the transmission. If the gearbox has "pan" then it's not a 5-speed.

 

Sorry Double G, maybe I wasn't being specific enough on the trans........what I meant was if I knew it was a typical Datsun 620 truck or Z car/Maxima trans, and the gear lever would go into a 5th gear slot above reverse then I would be more than certain it was indeed a 5 cog trans :) (assuming you woulda already dropped the stick into the other four forward gears to be sure :D:D)

Also, the 620 truck trans I know of with that pan you mentioned would be the "monkey motion' unit that is common to the 510 too.

 

So many fun vairiables to chose from.

--Ray

[jwerty1]

wish some of you guys were on the east coast. seems no one has a trans for sale out this way. I may not purchase a 5 speed yet, but I at least need a clutch kit, any recommendations? I want to drive this truck to work and back the days i cant drive my scooter. I think my slipping clutch might be attributed to a rear main leak. I must have put the new seal in cockeyed, or the rubber for the rear most main cap is really important and rtv won't seal it.

[ggzilla]

Get a valeo clutch kit. inexpensive but good quality.

[datzenmike]

Why's that? The 'traditional' model year starts in October. And many years Datsuns changed in October too.

 

The 1974 factory service manual only lists the L18.

 

Yes I keep forgetting back then the model year change was 'all over the place'. Usually it's July/August.

[DatDoug]

Its hard to beleive that your "New" clutch is slipping. Did you replace just the disc? If so you need to get the whole clutch kit. Disc, Throw-out bearing, Pressure Plate & Alinement tool. You could also replace your slave cyl. Cheap & easy $20.

 

Oh yah......SHOW US SOME PICS OF YOUR TRUCK after you read some more of the Ratsun Forum :D

[jwerty1]

I installed a new clutch disc and throwout bearing, should have installed a new pressure plate. However, when torn apart the clutch had no issues. Hope the pictures post ok. Some background 74 620 bought from original owners grandson. 60k original miles

 

http://www.facebook.com/media/set/?set=a.1607387200619.48056.1714371630&type=3#!/photo.php?fbid=1607391920737&set=a.1607387200619.48056.1714371630&type=3&theater[/img]

[Suspect]

I put a new clutch / pressure plate in my 77 and if you dump it too hard, it wouldn't hold it. It was from autozone.

[datzenmike]

I installed a new clutch disc and throwout bearing, should have installed a new pressure plate. However, when torn apart the clutch had no issues. Hope the pictures post ok. Some background 74 620 bought from original owners grandson. 60k original miles

 

http://www.facebook....&type=3[/img]

 

Should drop f/b and get Photobucket account for your pictures. Bigger better and always works.

[1lo620]

I have a 74, with a stock L18, I have a weber 32/36. with an Offenhauser intake, and a Z 5 spd and it runs out great. Drives awsome on freeway, and gets decent gas mileage. Good luck.!

[jwerty1]

Well, finally got to work on it a little last night. Apparently, clutch pedal height and master cylinder pushrod adjustment are quite important. I figured I would try any and all adjustments before I rip the trans out again. The pedal height was about 1/2 an inch too high and the clearance to the mc pushrod was not good. Drove it today and no slippage whatsoever!!!

[jwerty1]

so I thought I had the pic thing figured out.... the pics showed up on my preview of my post, but then after attempting to post it says you are not allowed to use that image extension on this board, wtf?

 

 

[datzenmike]

Thank you for the replies, its been a while. My truck started making a knocking noise down low at idle. Ripped it out, found it was the flywheel bolts came loose. Slapped it back together with some new gaskets, oil pump, repaired floor pan, new carb. Now my clutch just started slipping with a new clutch disc. So I'm finally back in the market for a trans upgrade. No I do not know how to tell a 4 sp from a 5 sp just by looking at it.

 

All 620 four speeds have a rectangular cover plate just forward of the shifter. It is held on with 6 bolts and has a small flat breather cap

 

 

 

The 5 speeds do not have the cover plate.

 

 

 

You cannot tell by shifting it into '5th' above reverse. The shifter bushings are getting old and sloppy and the shifter may go there but doesn't mean there is a gear there.

 

 

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