8.5 rear end identification

[pontiacgp]

Ok. So the g body has a rear everybody looks for which is the 8.5 rear. It came in Cutlass 442's, Grand Nationals, Ttypes, and Ive heard rumors that some elky's had them. They are hard to find and 1500 for a good drop in one thats 30yrs old. Some guys use old school 12 bolts with conversion upper control arms but the rear is too long. Or you need different offset wheels. The ford 8.8 can also be used, just like the 12bolt with some conversion control arms but again the lengths are wrong. So basically what Im saying is how hard is it to narrow one of those rears to the right length and be able to use the wheels you already have if you cant find a 8.5 at a decent price? Now I know this isnt true for everyone but for me if I can find a 12bolt posi for cheap enough the labor to narrow the rear will cost me almost nothing, then all I need is to buy axles for the 12bolt in the correct length. You can get Currie or mark williams to make what ever axles you want, you just have to give them the info they need.
Next and actually the most important question I have is how well do the conversion control arms work. Will the diff travel up and down properly, will the driveline angle be correct? Can you expect it to hook up like an original gbody rear or will it give you exessive wheel hop.
As I proof read this Im probably just going to confuse you even more. Anything you dont understand I will be more than happy to explain to you. But with all these questions answered one can make a better decision on how to spend there money based on there needs.

the A body Chevelle 1964 to 1967 12 bolt or 10 bolt is 2.5" wider than a G body rear. I have a 67 Chevelle rear with AR Torque Thrust II 17x8 rims with a 4" BS and 245-50-17 tires. The car is lowered a few inches as well. I had to roll the lip of the fenders just little but the these rims come with a deeper BS if you need it. I bought my rims used so they are what they are. The UMI adjustable conversion uppers and UMI lowers with a Roto joint on the axle side work great.

 

[Dinosport]

the A body Chevelle 1964 to 1967 12 bolt or 10 bolt is 2.5" wider than a G body rear. I have a 67 Chevelle rear with AR Torque Thrust II 17x8 rims with a 4" BS and 245-50-17 tires. The car is lowered a few inches as well. I had to roll the lip of the fenders just little but the these rims come with a deeper BS if you need it. I bought my rims used so they are what they are. The UMI adjustable conversion uppers and UMI lowers with a Roto joint on the axle side work great.

Sweet, Im going to look into what it would take as far as getting one of those rears and narrowing it to the proper length for a gbody, When I have it all figured out, cost of the rear, the control arms, custom axles Ill post it to a new thread just for information that guys can use.
Thanks

 

[pontiacgp]

Sweet, Im going to look into what it would take as far as getting one of those rears and narrowing it to the proper length for a gbody, When I have it all figured out, cost of the rear, the control arms, custom axles Ill post it to a new thread just for information that guys can use.
Thanks

I posted it earlier that the problem wit GM axles is the splines are cold rolled so you can't cut and re-spline them like you can with a Ford axle cause those splines are machined. I found the 2.5" wider rear provided more stability when cornering.

 

[Dinosport]

I posted it earlier that the problem wit GM axles is the splines are cold rolled so you can't cut and re-spline them like you can with a Ford axle cause those splines are machined. I found the 2.5" wider rear provided more stability when cornering.

Yes I read that. So that means that for the GM rears you would need to buy new axles I guess. You can get axles in any length you want. Obviously it wont be an off the shelf fair priced one. It will be custom making it more expensive. I have a few ideas on how to do it. It wont be super cheap but it might be less than buying a brand new 9". Or it might not be. Ill do some research and post it. Then guys can decide what will work better for them. Guys with low mechanical skill level may be better off buying one done, while guys with decent skill level might have a new option to obtain what they want.

 

[Travis Clark]

the brake drums on your Chevelle rear end are interchangeable with the G body drums . The problem you may have is the backspacing may not be enough on your rims

PontiacGP. When you say backspacing on the rims. Can you please expand on what you mean? I do not understand the term. I understand that if I use the wider rear end I will have to account for 2 inches expanded on each side. This is moving the stocks further outward from the frame correct? If this is the case, would I have to increase rim size? Would I be able to use the Blazer disc brake upgrade on the rear since the calipers shouldn't hit the frame with the extra 2 inches?

 

[pontiacgp]

PontiacGP. When you say backspacing on the rims. Can you please expand on what you mean? I do not understand the term. I understand that if I use the wider rear end I will have to account for 2 inches expanded on each side. This is moving the stocks further outward from the frame correct? If this is the case, would I have to increase rim size? Would I be able to use the Blazer disc brake upgrade on the rear since the calipers shouldn't hit the frame with the extra 2 inches?

If you asking about the 68 to 72 A body rear end the shock mount is virtually in the same place. That is why you can use the stock lowers even thought the rear end is wider. Backspacing on a rim is this....

 

[Travis Clark]

If you asking about the 68 to 72 A body rear end the shock mount is virtually in the same place. That is why you can use the stock lowers even thought the rear end is wider. Backspacing on a rim is this....

Ok, so the wider rear would not affect the use of my stocks. I've seen people talk about the wheel wells or fenders so I was unsure if it would present a problem. Thanks.

 

[Travis Clark]

More pics of this reported 8.5

 

[pontiacgp]

Ok, so the wider rear would not affect the use of my stocks. I've seen people talk about the wheel wells or fenders so I was unsure if it would present a problem. Thanks.

JBrue has a 68 to 72 A body rear in his Monte and he is always very helpful so you can ask him about any issues

 

[565bbchevy]

I am going to say for a novice looking for a strong rearend and without the means to modify one then the best bet is a bolt in Ford 9" housing that is available from multiple vendors, it bolts in like your stock rearend using all of your factory control arm mounting points, the shocks and springs mounts are also in in factory locations, it has the same GM wheel bolt pattern and the same width as your stock rear so you don't need to buy new rims with deeper backspacing and the best feature is the drop out center section that will fit in a milk crate and you can take it to your local rearend place and they can set it up with gears etc. without the need for the entire rearend assembly.