84' GN Rearend ?

[565bbchevy]

There is a guy on FM is selling a rear from a low mile 84' GN with a 3.42 gear but says it is a 7.5"
Is there any documentation showing that all 84' and up GN and TT"s came with 8.5 rears?

 

[1320John$$$]

There is a guy on FM selling a rear from a low mile 84' GN with a 3.42 gear but says it is a 7.5"
Is there any documentation showing that all 84' and up GN and TT"s came with 8.5 rears?

84 TT are 7.5 from what I found

 

[85ss/85gn]

All 84-87 t-type and grand national come with 8.5"

 

[565bbchevy]

All 84-87 t-type and grand national come with 8.5"

That is what I have always thought but can it be proven?

 

[Streetbu]

It's easy to determine just by looking at the "ears" on the bottom.

 

[85ss/85gn]

I have parted out 2 84 t-type and both were 8.5". And have other 84 t-type it has a 8.5"

 

[69hurstolds]

If original, check the SPID- G87 is 8.5" rear gear. G89 is 7.5"

T-types and GN for 1984 came with 8.5".

But make darn sure it's an 8.5". 7.5" have ways of getting under cars they shouldn't have after this many years. The 8.5" has "right angle triangles" under each side of the rear cover. The 7.5" has "fangs".

G-body cars that came from the factory with 8.5" ring gears:
1984-1987 Buick Turbo Regal/Grand National
1985-1987 Oldsmobile 442
1984 Hurst/Olds

Contrary to some beliefs out there, the 1983 Hurst/Olds came from the factory with 7.5" ring gears with the 3.73 drive ratio.

 

[Longroof79]

....unless of course the guy changed rear ends over time. You'd still have to eyeball it yourself....or if he's a distance away, at least have him take pics of it and send it to you,

 

[565bbchevy]

It's easy to determine just by looking at the "ears" on the bottom.

It would be but with only one picture no, I don't doubt it is a 7.5" only that it came out of a 84' GN.

 

[ck80]

It would be but with only one picture no, I don't doubt it is a 7.5" only that it came out of a 84' GN.

View attachment 131799

It may have come from an 84 gn, but it wouldn't have been original. Among the mandatory/non-optional equipment with the engine was getting the 8.5 rear, and, only in a 3.42 gear ratio. You couldn't switch the trans either.