trans recommendation ?

[benzo]

Hi all

 

I have a 71 wagon with the stock rear end which I believe are 3.70 gears. I have a long rod motor and it makes good power and torque but I feel my trans may be holding the engine from getting the power to the wheels. I believe the car has a 81 280 ZX trans and I suspect the gear ratios may not be a good match for this motor and rear end. I am running 14" wheels. I am wondering if some of you out there may have some info that may help or may recommend a trans that may get the power and drivability correct.

 

Thanks

 

Benzo

[datzenmike]

The '81-'83 280 tyranny is known as a close ratio. This means first is lower and all the others are closer together. The lower first makes it slightly more difficult for take offs. The advantage is that once moving there is less RPM drop on each shift. This is a great tranny for racing where there are few stops.... not so great around town. Additionally the close ratio has a monster over drive 5th gear of under .8 causing such a top speed RPM drop that smaller motors have difficulty pulling themselves along up hill or into the wind.

 

The '77-'80 tranny is a wide ratio and has a much lower 1st with wider spaced gears and a more respectible over drive. Take offs are easier with the lower 1st but there is more RPM drop between gears. Highway cruise has a slightly higher RPM which allows it to pull the car easier. These trannys were for much larger 2.8 liter engines with lots of torque and their dissadvantages are more noticable in a 4 cylinder car.

[benzo]

thanks Datzenmike. seems I would either need to change trans or rear gear or just live with it. curious if I change to the 77-80 trans do I need to mod the drive shaft. i assume not.

 

Thank you

 

Benzo

[datzenmike]

First identify your tranny. If it's an '81 or newer the tail stock will look like this one below:

 

LOOK FOR THE SPEEDO PINION LOCK BOLT ON THE BOTTOM.

http://i138.photobucket.com/albums/q251/datzenmike/transZ5speedlatecloseratio.jpg[/img]"] (note the extreme 0.745 over drive)

 

See if you have this tranny first. If you do, or not, and want some bottom power and torque I would change the rear end. This is way easier than you think and cheaper than hunting for another tranny. The 510 wagon uses an H-190 differential same as the 620/720 so there are lots of ratios to choose from. I would think if you have the close ratio tranny with the big O/D 5th then you could run a 4.11 and as high as a 4.375. If you have the wide ratio and not as tall an O/D 5th a 3.889 up to a 4.11 would work nice. There is one difference between wagon and truck differentials. The side gear splines are different, but the wagon side gears can be swapped into the truck differential to make this work. No shims or gear lash has to be set or adjusted it's just straight unbolt and swap.

 

IF,... you have a 280z tranny in there now a '77-'79 will be the same length. The 510 used the same short 4 speed as the car so if you have a 280z 5spd then it's already got a modified drive shaft.

Edited October 28, 2008 by datzenmike

[slodat]

Some 720's had a 3.7 rear gear ratio. The ratio is on the cowl tag. A 3.7 would be 37.

[ppeters914]

So, it sounds like either would work with the L20b in my WPL411, which has a 4.11 rear end, correct?

 

If you are thinking of using these 280z trannys it will depend on what you have in there now. These trannys are 31.5" long so if the tranny you have is that long it will work without changing the drive shaft length.

 

I have no idea what rear end is in a WPL411. A 4.11 does not sound very low and would expect at least a 4.375 and maybe a 4.88 depending on what the original motor size was.

Edited November 8, 2008 by datzenmike

[benzo]

Yeah thanks for this info and I saw a post with the pic and I do have a 81 zx trans. yeah my first gear starts are a bit weak and my fifth gear is good on the freeway. I think maybe looking for a truck rear end with different gears may be what i need to do. I am thinking the 4.11 ratio.

 

thanks for the feedback.

[benzo]

Hi Datzenmike

 

thanks for the info last time. I had a question. if I go to a junkyard what year truck should I look for to get the rear end with the 4.11 gears? I am not sure what the truck body looks like and what I should look for on the rear end. also could I just change out the center chunk without changing the whole axle on the wagon? I believe I heard or was told I can do this.

 

Thanks

 

Benzo

[datzenmike]

Hi Datzenmike

 

thanks for the info last time. I had a question. if I go to a junkyard what year truck should I look for to get the rear end with the 4.11 gears? I am not sure what the truck body looks like and what I should look for on the rear end. also could I just change out the center chunk without changing the whole axle on the wagon? I believe I heard or was told I can do this.

 

Thanks

 

Benzo

 

a 4.11 would work nice. There is one difference between wagon and truck differentials. The side gear splines are different, but the wagon side gears can be swapped into the truck differential to make this work. No shims or gear lash has to be set or adjusted it's just straight unbolt and swap.

 

As noted above, you will have to swap your old side gears, (the ones that the splines on your axles slide into, the truck's are different from the wagon) out of your rear and into the new rear. It's not rocket science.

 

Nissan differentials do not have tags with the ratio on them. Trucks with 4.11 rear gears are:

 

'79 620 (round head lights) standard tranny (radio aerial is on driver's side)

 

'80-'83.5 720 2wd (square head lights)

Check the credit card sized aluminum tag located on the passenger inner fender just below the hood hinge. It will have info including the axle ratio stamped in it like this:

 

http://i138.photobucket.com/albums/q251/datzenmike/720stuff034Large.jpg[/img]"]

 

Near bottom is TRANS/AXLE......... FS5W71B...............HF38

The 38 stands for 3.889, 43 is for 4.375, 37 is 3.700 and so on, you want 41 for 4.111

[benzo]

thanks for the info. I did some searching and that helped show me pics of what to look for. just to clear so I can confirm the visual pic in my head. I take wagon diff chunk out of the housing and take off the side gears and put that on the truck diff and put the truck diff chunk into my wagon axle housing? does this sound correct?

 

Thank you all

 

the pics help a lot. hopefully if I can do this I can chronicle all of the work to show others to help them

 

Benzo

[datzenmike]

Basically yes. Drive out the lock pin that holds the pinion mate shaft and spider gears. Remove shaft and rotate gears and remove them one at a time with their thrust washers, keeping them in order for re-assembly. Substitute the wagon side gears for the truck side gears and re-assemble using a NEW lock pin. You do not want this pin coming loose!

[hang_510]

I have a 71 wagon with the stock rear end which I believe are 3.70 gears.

 

IIRC stock wagon rear end is 3.889

[benzo]

Hey Hang 510

 

what is llRC Wagon? not sure what you meant?

[datzenmike]

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