Rear End 8.5
- Thread starter Drew8509
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this is what i found. maybe this helps?
1978 - 1988
First, ALL GM 1981 to 1988 G-Bodies used a 7.5" ring gear rear axle EXCEPT: Monte Carlo SS - 7-5/8" 3.73, Olds 442 - 8.5" 3.73, T-Type and Grand National - 8.5" 3.42 or 3.73. The 8.5" axle is the same used in the B-body (full sized) except a shorter axle tube length. Second, the 7-5/8" axle is actually used in the mid 80's F-bodies Camaro & Firebird. This axle is the one used in the Monte Carlo SS. Third, the '80s S and T trucks use a 7.5" ring gear axle. A short trip to the service manuals on these vehicles is all it takes to check this information out.
The 442 and Regal axles are hard to find because 442s are rare and most T-types and Grand Nationals are not junked yet. For older Cutlasses, the B-body 8.5" axle might fit better than the G-body axle.
1978 - 1988
First, ALL GM 1981 to 1988 G-Bodies used a 7.5" ring gear rear axle EXCEPT: Monte Carlo SS - 7-5/8" 3.73, Olds 442 - 8.5" 3.73, T-Type and Grand National - 8.5" 3.42 or 3.73. The 8.5" axle is the same used in the B-body (full sized) except a shorter axle tube length. Second, the 7-5/8" axle is actually used in the mid 80's F-bodies Camaro & Firebird. This axle is the one used in the Monte Carlo SS. Third, the '80s S and T trucks use a 7.5" ring gear axle. A short trip to the service manuals on these vehicles is all it takes to check this information out.
The 442 and Regal axles are hard to find because 442s are rare and most T-types and Grand Nationals are not junked yet. For older Cutlasses, the B-body 8.5" axle might fit better than the G-body axle.
RPO |--------Axle Code--------|
Ring Gear Code Ratio Conventional Limited Slip
-------------------------------------------------------
7.5" G72 2.14 2AK 2BK (aluminum brake drums)
7.5" GH2 2.29 2AH 2BH
7.5" GU1 2.41 2AJ,2AZ 2BJ,2BZ
7.5" GM8 2.56 2AA 2BA
7.5" GU2 2.73 2AB,2AX 2BB,2BX
7.5" GU4 3.08 2AC,2AV 2BC,2BV
7.5" GU5 3.23 2AD 2BD
7.625" GT4 3.73 2TF 2TH (Monte Carlo SS)
8.5" GU6 3.42 3TP 3TJ (T-Type, GN Std.)
8.5" GT4 3.73 3TG,3TE 3TR,3TX (442, GN Opt.)
8.5" GU2 2.73 8YB 8YP (B-Body)
8.5" GU4 3.08 8YD 8YR (B-Body)
8.5" GU5 3.23 8YE 8YS (B-Body)
If you don't have the codes with you to indentify if it is an 8.5" or not, I found that if you measure the distance between the very bottom bolt for the cover and the next adjacent one (either right of left), it will be 3 ¾" for a 8.5" and 3 1/4"
Ring Gear Code Ratio Conventional Limited Slip
-------------------------------------------------------
7.5" G72 2.14 2AK 2BK (aluminum brake drums)
7.5" GH2 2.29 2AH 2BH
7.5" GU1 2.41 2AJ,2AZ 2BJ,2BZ
7.5" GM8 2.56 2AA 2BA
7.5" GU2 2.73 2AB,2AX 2BB,2BX
7.5" GU4 3.08 2AC,2AV 2BC,2BV
7.5" GU5 3.23 2AD 2BD
7.625" GT4 3.73 2TF 2TH (Monte Carlo SS)
8.5" GU6 3.42 3TP 3TJ (T-Type, GN Std.)
8.5" GT4 3.73 3TG,3TE 3TR,3TX (442, GN Opt.)
8.5" GU2 2.73 8YB 8YP (B-Body)
8.5" GU4 3.08 8YD 8YR (B-Body)
8.5" GU5 3.23 8YE 8YS (B-Body)
If you don't have the codes with you to indentify if it is an 8.5" or not, I found that if you measure the distance between the very bottom bolt for the cover and the next adjacent one (either right of left), it will be 3 ¾" for a 8.5" and 3 1/4"
ERIC87442 said:
Not the same, I had thought this, so I went to a yard and plucked an 8.5 lmtd slip 3.42 from an ex cop car, spring perches are in the right spot, but the upper control arms angles are completely different, the ears are more or less on the side of the diff closer to the front, and the lowers would need to be relocated as well along with a different shock mount. I was pissed when I took a closer look, when I got home with it.
Agree possible to swap in, but much extra work to get it "right", I didn't have time to try it, (i rely too much on my bu)lol. so I opted for the direct bolt in 8.5 from a 442.
It is the internet.... And we all know that someone will be along to correct us shortly. Regardless of the situation in question.
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