best rear gear for lz24 in 521

[datsunfish]

Getting everything setup for the LZ24 swap in my 521. Its got a 488 in it and it sucks. Thinkinng about stuffing in a long shaft 4 speed since the shorty probably wouldnt last too long. A 411 should be good but would a 720 rear gear swap into the 488 housing? Thats in the 3s right? or would that be a dog? Appreciate any input.

[jesusno2]

Depends on how you want the truck to preform. With only a 4 speed trans, I would opt for a 3.70 or 3.90 ratio. With a 5spd trans I would opt for the 3.90 ratio. Wheel ,and tire size plays a big factor into gear ratios also, but the best gear I've found is defenetley the 3.90 or a 4.11 if you can find one, Their fairly uncommon.

[datsunfish]

cool thanks.. I really just want longer shift intervals. I think the 2.4 should pull hard through the lower rpms and the L head and carb will help it rap up well but still wanna do a burnout here and there. I can find 720s around here any day easy. I prefer to keep the narrower 488 housing though. Is it safe to assume that the 3.7 or 3.9 will bolt in fine?

Hmmm I think I will hit the yard tomorrow. There is one around here open on a sunday and thats pretty cool.

[datzenmike]

520/521/620/720 2wd should fit just fine and also have the correct side gear spline. The '79 620 standard had 4.11s and Z22 720s with autos usually. Z24 720s with 4X4 had 4.11 but the one I had used a different yoke for the larger U joint drive shaft. I tried to swap the 2wd yoke on but the pinion had a different spline. Stick to 2wd 720s. The good thing about 720s are the gear ratio in the back is stamped into the engine tag.

 

 

Bottom right corner HF38.... HF is an H-190. 38 is a 3.889 ratio. 41 would be 4.11, 43 is 4.375 and so on. The engine tag is under the pass side hood hinge on the upper inner fender.

 

720s with Z24s ran 3.889s but this was for mileage mostly. At least it had the stump puller Z24 motor. On a much lighter 521 it should go much better.

 

Just an opinion but I would run 3.889 with a 4 speed and 4.11 with a 5 spd. The 5 speed would have the overdrive 5th to make up for the lower 4.11s on the highway..... have your cake, and eat it too!

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[Z-train]

I'm putting 3.88s behind my LZ-23.Should be about perfect.