clm69z28

I have a 72 Chevelle 'vert with the 8.2 non posi 2.73 factory rear end with a stock LS1 with a 4L60E transmission from an'00 Camaro SS. I have found a 68GTO rear end with 3:55's and an Eaton posi for a good price and would like to know the swap issues and if the application would work. The car is just a fun cruiser with a lot of coast cruising and some freeway, so I am not too worried about the ratios- the calculators say around 2,559 revs at 80 with the OD. What do you all think of it?

Bowtie70SS

iTrader: (10)

A 3.55 gear is pretty decent for all around driving. You can also vary the cruise RPM with tire diameter.

Dave

clm69z28

Bowtie:

I thought that the ratio would not be too "short"- the current 2.73's must be good for about 150 mph!!

Anybody have any opinion/experience with this rearend swap? The rearend is already set up and so it would be relatively easy if it fits. I understand that the yoke may need to be changed and the driveshaft shortened; any other things I should consider?

claytonisbob

iTrader: (1)

My understanding is 68 to 72 A-Body's have the same rear-end width and brackets. The earlier ones (64 to 67, ect) are a little narrower.

70cartruck

iTrader: (1)

i have my 8.2 with 3.55's.....pretty much the perfect street/strip gear for what i do with the car.......i have a th350 tho....wish i had overdrive....

bczee

iTrader: (12)

I would say the 3.55's are a good alround gear. It shuold swap in and be the same hub to hub width. As stated, the earlier A-Body were one inch narrower (56.5 vs 58.5).

You can usually tell the difference by the cover.. the BOP is irregular in shape and the Chevy has a more oval shape with a V in the cover. I think most of the internal are interchangable. (could be corrected ?)
There is also some difference in the BOP vs. Chevy rears.. but I don't recall what the differences are and if your not into Numbers matching or correct parts.. it would not make any difference then.

edit, just noticed I forgot to state, it is 1" per side.. (56.5" vs 58.5" hub to hub)

Bowtie70SS

iTrader: (10)

I have 3.31 gears in my Elcamino and no overdrive with the stock 14 inch SS wheels. My cruise RPM at 80 is 3000. With overdrive it would be 70% of that or 2100rpm. I put a 3.55 gear in my Chevelle with a MN12 (6 speed) with the double overdrive I could hit 150+ no sweat.

Hodge

iTrader: (2)

I've owned seven A-bodies over the years. This is what I can tell you about rearend interchangeability:

1. All 64-72 A-body rearends are interchangeable. That is they physically mount the same way.
2. 64-67 A-body rearends are the same width.
3. 68-72 A-body rearends are the same width. these are about 1" wider than the 64-67 rearends.
4. There are two sizes u-joints used. do not remember the spicer numbers of the u-joints. The "small" u-joint uses EXTERNAL clips to hold it in place. The "large" u-joint uses injected plastic to hold it in place. If the "large" u-joint has been replaced, it is held in place with INTERNAL clips.
5. On Chevy rear ends, powerglides, TH-350s and early muncies (pre 1971) use the "small" u-joint. TH-400s (67 and up) and 71 & later muncies use the "large" u-joint.
6. #5 isn't true for BOP (buick, olds, & pontiac). My 66 GTO had a dual path trans (I think it was called a dual path; it was the pontiac version of the power glide) and had the "large" u-joints.

The u-joint differences is NO problem. Spicer makes an adapter u-joint that will mate the different u-joint sizes. Do a google search to find it. As far as the width difference, I would not worry about it either. If you have interference due to the rearend witth, there are many aftermarket wheels with custom offsets. I put custom offset pontiac mags on my 66 GTO in the mid-90's. Very reasonable back then.

clm69z28

Thanks everybody for the input. I think I have decided to just upgrade my original rear end with an Eaton posi and either a 3:36 or 3:55 gear ratio. Since it is basically a stock 'vert w/an LS1, I don't plan on doing any real drag racing with it so I am leaning toward the lower gear set. I actually had a driveline shop recommend 3:73's with the OD and I thought that shounded way too short for this ap....