gearing help in my pl521!

[dirty-mik3]

so i'm completely new here, iv scanned the forums numerous times before and i'm on the site about everyday. but i cant find really what i'm looking for..

a little back-story: my father bought a 72 pl521 with a stock l16 for $400.00, was planning on using it for parts for his 521, but i decided i wanted a fine piece of datsun machinery as well, :thumbup: so i decided to buy it off him. Bear with me, as i am 16 years old and don't COMPLETELY know my way around engines/transmissions, i know a fair bit, but definitely not everything. :blush: i really want to build a sporty little truck that will be fun as hell to drive. for now, a cam is being ground down in the shop, i have a weber, and i have 195/50/15's on hold, i'm picking up some chevy ralleys hopefully this week. :D so my question to you guys, is what diff ratio should i go with? and what rear end would i find it in?! :huh:

thanks! mikey

 

ill post pictures once im motivated :)

[thisismatt]

...and another one bites the dust

[dirty-mik3]

i apologize if there is already a thread explaining it.. could you possibly point me in the right direction?

[DanielC]

You have two easy choices with the 521. leave the stock 4.375 rear end in the truck, and avoid bigger tires.

 

If you can find a rear end out of a 520 or early 521 with the J-13 engine, it will have a 4.875 rear axle ratio.

 

If you are not motivated enough to bother to post pictures, just get the truck running without making this a big huge project.

[datsunaholic]

Your rear differential is a H190 (a H190-AL to be specific, though you don't NEED to keep the aluminium carrier). Start your searching there.

 

The rear ratio you have is just fine for general purpose. It's a 4.375, one of the most common ratios for the type of rear you have, used on almost every truck from 1970-1978 with a couple exceptions, If you want faster acceleration, go lower (higher numerically, like a 4.88, which is found in 66-69 trucks). If you want slower acceleration but better highway cruising, go higher (such as 4.11 or 3.89) which are commonly found in 1979 and newer trucks up through around 1987 when the diffs changed to a different type on some.

 

HOWEVER... get it running FIRST. Then decide which end of the spectrum you want to improve, because you'll make the other end worse with a diff change.

[dirty-mik3]

alright! thanks a ton! :thumbup:

[datzenmike]

The 195/50R15s are just slightly less than one inch smaller than the stock 6:00 x 14s that came on the 521, so tires and rims choice won't really hurt this. Stick with the stock rear end.