I recently changed the rear end fluid on my original 87 Turbo T with 69k miles and when i went to install the gasket that i bought for a 87 GN with 8.5 rear it was too big! I returned to the store with the rear end cover and tried a gasket for the 7.5 rear and it fit perfect. I thought all Turbo cars came with 8.5 rears, is it possible that my car came with a G80 7.5 rear??? Steve
'87 Turbo Regal with 7.5 Posi Rear?
- Thread starter SEP455
- Start date
Really???
Agreed with above, really? Good to know and not that uncommon in building cars even today. That kind of info may be lost one day though.
Sorry, car was built on 12-3-86. I know that some 8.5 rears had premature spider wear issues, is it possible that rear was swapped out under warranty at some point?
novaderrik
Well-Known Member
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- May 12, 2004
and they just happened to have a pile of G body 7.5's laying around with 3.42 gears and posi differentials in them?
Its a real Turbo T, someone probably swapped out, but I never heard of 342 gears in 7.5 rear?
turbonut85
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- Apr 11, 2008
Did you count the teeth and verify its actually 3.42? Could be 3.23 or 3.73.....
My 84 Z28 had a 7.5 open diff, and I'm sure it had 3.42's
5 speed Lt1 F-bodies had 3.42's They were 7.5"
novaderrik
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- May 12, 2004
my 86 Camaro has 3.42 gears, and it orignally had a 2.8 V6 and an auto trans... F bodies are where to look for 3.42 gears for a 7.5 since they were the standard gear for most of the production run of the 3rd gens..
but i don't think they ever made a G body with a 7.5 that had better than 3.08 gears- most of them were 2.47 or 2.56 or something stupid like that- and i even saw one Malibu that had something like 2.21 gears.. that car was a slug out of the hole but had one hell of a top end charge..
but i don't think they ever made a G body with a 7.5 that had better than 3.08 gears- most of them were 2.47 or 2.56 or something stupid like that- and i even saw one Malibu that had something like 2.21 gears.. that car was a slug out of the hole but had one hell of a top end charge..
After doing some research, I was told that they made different 8.5 rears that had slightly different rear end gaskets. This was because some 8.5 were the Eaton clutch type while others were the Auburn cone type which had a slightly smaller gasket. The Felpro catalog listing shows a 8.5 and 7.5 gasket for the 87 GN to differentiate between the two types. I am going to confirm this by physically measuring the ring gear. Thanks for all your feedback.
marked driveshaft and confirmed 3.42 that way
novaderrik
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- May 12, 2004
that Fel Pro listing is a generic G body listing, not a GN specific listing. the GN and other TR's used a regular corporate 8.5 just like millions of other GM cars and trucks built since 1972 or so, except in a housing that was cast with the G body suspension geometry.. on the inside, a corporate 8.5 is a corporate 8.5- and they use the same cover gasket regardless of what guts are inside. that same gasket also fits the 8.5 used in late 70's and newer 1/2 ton pickups (probably up to the current model year), every second gen F body ever built, some later S series trucks and blazers, and even the 94-96 Impala SS. it also fits the corporate 8.2 that was used in the 60's and early 70's in A,F, and X bodies... there was the BOP 8.5, but those used a different cover and had pressed on axle bearings.. i doubt if there was ever a G body version, but it was used in B bodies until the mid 80's some time..
but i don't use the gaskets any more... a bead of The Right Stuff is what GM has used since the late 80's some time, and it's what i use..
I checked the trunk codes: G87, G80, GU6 which would indicate 8.5, posi, 342 rear, however, codes on axel housing dont match: 6BS C170 2 ?
Can anyone interpet the axel codes for me? Pic to follow.
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