Chevelle LS1 Rear End Swap Questions
#1
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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?
#3
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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?
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?
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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)
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)
Last edited by bczee; 05-05-2010 at 12:27 AM.
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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.
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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.
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.
#9
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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....