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Rear end gearing question

2K views 6 replies 5 participants last post by  veno 
#1 ·
hey guys i have a rear end that i'm going to be putting a posi unit i got outta a 71 camaro into and this rear end is stock with my nova is a 8.5 10 bolt and it has 3.08 gearing

my question is is that gearing fine to keep?

im going to be running a m-21 with a 2.20 first gear and i did the graph and i can be in first gear at like 30mph still in the 2000-3000 rpm range

this means at highway speeds ill be cruising in the 2000-3000 rpm range as well which will be really good for gas mileage

this isn't going to be a drag car by any standard nor a long distance car but i want it to get decent gas mileage and be fairly peppy off the line

with that info...

will i be fine with 3.08 gearing? or should i go higher to 3.73 gearing? what would be the pro/cons? -- the 3.08 ring and pinion are in good condition so its not like they need to be replaced.

thanks! :yes:
 
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#2 · (Edited)
#5 ·
As noted, a 2.20 first gear with a 3.08 rear end is not exactly a good combo. Either go more rear gear, like 3.42 maybe, or go with a wide ratio trans with somewhere around a 2.52 first gear if you want some off the line performance.
 
#6 ·
i know the camaro rear end is larger im just using it for a posi locker donor for my nova rear end so no worries there!

as for the gearing how much more "pep" will i get out of 3.73 gearing? i dont know how to describe it any more than just "pep" but thats my only concern.. as i mentioned previously its not gonna be a drag car and im not even gonna take it to the strip i just dont want it to be really slow getting up to speed off the line so i want a decent amount of peppiness and i was just wondering if the 3.08 gearing would give me sufficient pep.. does that make sense?
 
#7 ·
ok... the 220 low first gear(close ratio trans) from GM were usually installed with the performance ring and pinion option.(3.73 and up) remember the power band on these cars was narrow. for your app a the 256 wide ratio would be a better choice.... however; the 3.08 will be fine... you will just shift sooner than the wide ratio would need to be... Smooth take offs will be a practice... but you will get it down....

It will be fine... run the 3.08s if thats what you really want to do.... it wont hurt any thing. just a note... take the posi apart for inspection....and clean it... its not that hard.... you might want to invest in a new clutch and steel kit for a rebuild... just a thought.... most of those LSD's are very tough.. and are in relatively good shape even with 30 years on them.
 
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