7.5 / 8.5 rear end

[spoolinturbo6]

does anyone else have a 7.5 rear that came factory in a 86 turbo regal?
I am getting different info depending on who I talk to. someone said all turbo buicks from 84 to 87 came with a 8.5 then someone else said that some did come with a 7.5 ???? well none the less I need an 8.5 rear housing. or I will sell my complete new setup from strange and buy a ford 9".

 

[TryMeGT]

Grand Nationals came with 8.5 10 bolts. If yours has a 7.5, then it has been changed out for some reason or another

Quote from GNTTYPE.org
All 1984-1987 Turbo Regals were equipped with GM's 10 bolt 8.5" rear end. The great majority of them were equipped with 3.42 gears, although there are documented cases of a few of the early cars having optional 3.73 gears. Positration was an option G80 in all years, however the "late build" or "extended run" Grand Nationals that were built in 3rd and 4th quarter of 1987 had the G80 bundled into the Grand National package.

 

[RobsIron]

All TR's are 8.5s.

Unless you are often running 10s or better with slicks..throw a 8.5 in there.

Puts more HP to the ground.

 

[spoolinturbo6]

8.5 rear

I am with you guys on this I think that all tr's came with the 8.5 just due to the fact that the tr's need a stronger rear. and Its not that I am not reading and understanding what you are saying but does any one have any hard documatation on this. because I called a true buick guru that said all turbo buicks from 84 to 87 came with 8.5 rears. then a company called DTS that sells gears, complete rears,and etc. stated that not all turbo buicks came with 8.5 some came with 7.5's?????? I am thinking that he was thinking of other g bodies like the monte ss. some did and some did not.

 

[TURBOPOWERED68]

All TR's are 8.5s.

Unless you are often running 10s or better with slicks..throw a 8.5 in there.

Puts more HP to the ground.

My Stock set up with just a built Trans and BS D7 broke apart a 7.5 with 373s and BFgoodrich T/As.
I wouldn't try to put any power to the ground with a 7.5 inch rear.

 

[spoolinturbo6]

rear end

This is my issue I bought this car drove it for a little, popped a head gasket. took the heads to a machine shop to have them checked. the heads have hair line cracks. installed new champion heads. decided that I did nott like other things about the car and so the tear down started. I got to the rear and ordered 33 spline axles, spool, c clip elim., new pinion,ring gear. ultimate rear end cover, cleaned the rear , stripped paint, sanded, welded the tubes to pumpkin, painted and looks like new. started to put back together only to find the pinion is 1" longer. WTF is this. well this is how I found out I had a f***** mother F***** 7.5 rear. now I am really pissed. so I am trying to do a proper build on my car. if someone put this rear in a car the was already running low 11's why would you do something so half ass. other than the money aspect. I get tried of seeing sh*t done half ass.

 

[spoolinturbo6]

ttt

 

[RobsIron]

All TR's are 8.5s.

Unless you are often running 10s or better with slicks..throw a 8.5 in there.

Puts more HP to the ground.

My Stock set up with just a built Trans and BS D7 broke apart a 7.5 with 373s and BFgoodrich T/As.
I wouldn't try to put any power to the ground with a 7.5 inch rear.

I think you misread my post.

I said to put a 8.5 in.

He was gonna go with a 9" and unless he's in the 10's running slicks all the time..go with the 8.5.


Spoolin, Go with the 8.5. It is pretty much a 12 bolt with a little smaller ring gear.

 

[spoolinturbo6]

8.5

thanks your help guys !!

 

[novaderrik]

I am with you guys on this I think that all tr's came with the 8.5 just due to the fact that the tr's need a stronger rear. and Its not that I am not reading and understanding what you are saying but does any one have any hard documatation on this. because I called a true buick guru that said all turbo buicks from 84 to 87 came with 8.5 rears. then a company called DTS that sells gears, complete rears,and etc. stated that not all turbo buicks came with 8.5 some came with 7.5's?????? I am thinking that he was thinking of other g bodies like the monte ss. some did and some did not.

not all turbo Buicks had the 8.5- the 78-83 cars all had a 7.5.
as for the strength of a 7.5- the Camaro guys can get them to live fairly well behind some pretty wicked LS1's.

 

[Boost231]

dont run a 7.5. i ran one in my mid 11 sec car and it didnt even last 1 weekend with an auburn on stock axels. it snaped the axle on street tires at the track. only was getting 1.60 sixty foots and it snapped.

 

[TURBOPOWERED68]

I think you misread my post.

I said to put a 8.5 in.

He was gonna go with a 9" and unless he's in the 10's running slicks all the time..go with the 8.5.


Spoolin, Go with the 8.5. It is pretty much a 12 bolt with a little smaller ring gear.

My Bad Dude.

 

[TURBOPOWERED68]

i would go to Monte Carlo SS Information & Resources and try to sell it somebody that might want to keep their car original.
Good luck Dude

This is my issue I bought this car drove it for a little, popped a head gasket. took the heads to a machine shop to have them checked. the heads have hair line cracks. installed new champion heads. decided that I did nott like other things about the car and so the tear down started. I got to the rear and ordered 33 spline axles, spool, c clip elim., new pinion,ring gear. ultimate rear end cover, cleaned the rear , stripped paint, sanded, welded the tubes to pumpkin, painted and looks like new. started to put back together only to find the pinion is 1" longer. WTF is this. well this is how I found out I had a f***** mother F***** 7.5 rear. now I am really pissed. so I am trying to do a proper build on my car. if someone put this rear in a car the was already running low 11's why would you do something so half ass. other than the money aspect. I get tried of seeing sh*t done half ass.

 

[VadersV6]

The guy I bought my car from- I told him that I would buy the car if he had the original gears put back in. So he called me from the shop where the mechanic said it had a 7.5 in it. I said I wouldnt buy the car, so he dropped 500 off the price. Getting an 8.5 in cost me 1300 bucks, but it was probably worth it. What was weirder was that the 7.5 was a posi with 4.56 gears. So I imagine that rear probably came from some 1/4 mile car, non TR, but apparently it had held up with a 4500 stall TC. There were many signs pointing to the possibility that someone had stripped all the good stuff off the car, and Im sure the rear was one of them. I had the 7.5 sitting out behind my work, and someone stole it about a month ago. Someone on this board probably knows who, but who cares? In the end it was a waste of time as I was never able to get to the point I could take it to the track and see what it could do, so the 8.5 never got any duty. Didnt matter since the 8.5 went peg leg within the first month. 7.5's can hold up to some power if built well with a girdle, good bearings, a good diff, welded axle tubes, good solid control arms and good axles, but by the time you dump that cash in, it would be cheaper to use a stock GN rear. A huge energy spike is what causes angular deflection between the pinion and ring gear, coming from the housing tweaking in relation to the axle tubes, making the axle tubes tweak or vice versa (the tube bends or the spot weld breaks), putting a huge load on the splined ends of the axles, which comes from weak control arms and soft control arm bushings...eventually the pinion separates enough from the ring, or the ring defects and seperates away from the pinion, putting the load on the outer end of the gears which is the weakest area, and POP goes the weasel. With all the hardware, yes it can hold up, but imagine an 8.5 with all that hardware.