Rear Axle Identification


G body LS mafia
Supporting Member
Nov 24, 2014
Louisville, KY
I'm going to look at a non-running 1986 442 tomorrow; If I were to pick it up, and bolt in the 8.5, would the driveshaft proper fit from a 200r4-8.5 to a TH200-7.5?

Don't believe so, the 8.5 has a longer pinion on it requiring the driveshaft to be shortened about an inch. At least i had to shorten mine an inch when i swapped out my 7.5 in my 87 cutlass to a 8.5 i got from an '85 442 with 3.73's in it. Hope this helps.
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Builder of Cool Shjt
Supporting Member
Feb 2, 2015
Calgary, Alberta, Canada
If you can, grab the driveshaft out of it when you grab the diff. Problem solved. That's what I did.
As far as the difference between the slip yokes from a TH200r4 to a TH200, I can't say. I went from a TH350C to a TH200r4. Maybe some other members can say yay or nay.


Living in the Past
Jul 19, 2009
Permanent Temporary
TH200C uses the same 27-spline slip yoke as the 200-4R, 700-R4, TH350 and TH250. The one that is different is the TH400.

I did just climbed under my coupe to measure the 8.5 yoke. It seems to use the same 534G U-joint as the 7.5, with the inner lock rings that fit into a groove in the caps. And I can back up that inch. That's about what it looks like I need to take off according to my current driveshaft. Just get the rear end of the driveshaft tube shortened and rewelded. I suggest new U-joints and a dynamic balance.
Last edited:


Aug 3, 2016
i bought a 84 cutlass 7.5 differential and tried to fit a 84 regal limited slip gear into it. the pinion started rubbing on the housing. would anybody know how to solve this problem?


Aug 3, 2016
top one is the regal differential and the bottom one in the new one.
original regal diff.jpg
chrome cuttlas diff.jpg


Mar 31, 2006
Kitchener, Ontario
the lower rear is an 8.2 and that's why the pinion does not fit..and it will be wider than your G body rear
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