Rear Axle Identification

Injectedcutty

G body LS mafia
Nov 24, 2014
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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?

Thanks!
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.
Scott.
 
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Rktpwrd

Builder of Cool Shjt
Supporting Member
Feb 2, 2015
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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.
 

ssn696

Living in the Past
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Jul 19, 2009
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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.
 
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tricrick84

Not-quite-so-new-guy
Aug 3, 2016
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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?
 

pontiacgp

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Mar 31, 2006
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then I do not understand how the pinion is rubbing the housing....pictures may help
 

tricrick84

Not-quite-so-new-guy
Aug 3, 2016
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top one is the regal differential and the bottom one in the new one.
original regal diff.jpg
chrome cuttlas diff.jpg
 

pontiacgp

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Mar 31, 2006
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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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tricrick84

Not-quite-so-new-guy
Aug 3, 2016
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Shiiit. That makes a whole lot of sense. Would you happen to know what it would fit on?
 

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