gm7.5 & gm8.5 rear questions

[bertscova]

I know this has probably already been covered but since i don't want to spend all day searching for all the answers I'll just ask all my questions in one post.
the car is a 79 malibu 383 stroker 500hp a 2004r full of goodies 3000 nonlocking converter. Rearend at this time factory 7.5 3.42 one wheel wonder

1.) What are the differences in the 7.5 and 8.5. I know the ring and pinion is larger in the 8.5. But what about axle size, bearing and seals, differential carrier ect.... will brakes from the 7.5 bolt to the 8.5

2.) Can the 7.5 be beefed up enough to handle what i have. No trans brake no line lock. I leave the line on footbrake

3.) With my set up and the correct size rear (7.5 or 8.5) will a 4.11 gear be to steep. Its a drive to the track car and some short local driving no interstate travel. Im going to use the detroit truetrack carrier. Rear tire is 26.8 tall

The car is still being built so only the engine is set in stone

 

[Garrett1982]

View attachment 46610 I know this has probably already been covered but since i don't want to spend all day searching for all the answers I'll just ask all my questions in one post.
the car is a 79 malibu 383 stroker 500hp a 2004r full of goodies 3000 nonlocking converter. Rearend at this time factory 7.5 3.42 one wheel wonder

1.) What are the differences in the 7.5 and 8.5. I know the ring and pinion is larger in the 8.5. But what about axle size, bearing and seals, differential carrier ect.... will brakes from the 7.5 bolt to the 8.5

2.) Can the 7.5 be beefed up enough to handle what i have. No trans brake no line lock. I leave the line on footbrake

3.) With my set up and the correct size rear (7.5 or 8.5) will a 4.11 gear be to steep. Its a drive to the track car and some short local driving no interstate travel. Im going to use the detroit truetrack carrier. Rear tire is 26.8 tall

The car is still being built so only the engine is set in stone

3.73 would probably be a better ratio for your tire size. I would keep an eye out for an 8.5 or maybe an 8.8 Ford rear out of a mustang, which are cheap and plentiful. They will fit with spring perches added and special upper control arms.

 

[Garrett1982]

http://www.richmondgear.com/1.html

This should help you figure out a gear ratio for the rear.

 

[bertscova]

That is a nice little calculator. But how accurate can it be since it doesn't want to know transmission gear

 

[lilbowtie]

If you putting out 500 HP your capable of high 10's - don't spend any money on a 7.5 rear.

 

[Garrett1982]

That is a nice little calculator. But how accurate can it be since it doesn't want to know transmission gear

I think it is calculating for 1:1, like third in a auto or fourth in a four speed. Should give you a rough rear gear estimate. I put in my weight, power, tire height and trap rpm and it said my desired gear is 4.09. The gear in my s60 is a 4.10. I didn't pay much attention to the et or trap speed.

 

[HAFROD]

I had emailed Strange or Richmond a few years ago about 7.5 rears. He said with a rear end cover with girdles up to 350HP is fine on a 7.5. I never have personally broke any 7.5s with slicks at the track but I just foot brake anyway. I know some that have though

 

[Garrett1982]

http://www.richmondgear.com/2.html

I also found this calculator. It is helpful to figure out gearing for street driving and cruising.

 

[79 USA 1]

My 79 Monte Carlo has been running a GM 7.5 with a Detroit Locker, Richmond 4.10 gears, Tom's KA 28 spline axles, Summit girdle cover and a 8.5 modified steel cap on the ring gear side for over 8 years on Mickey Thompson ET Streets.
While the 406 SB Chevy and turbo 350 trans.with 3000 stall converter make less than 500 HP, this set up has performed quite well for 8.10 sec 1/8 mile passes in full street trim.
These are the guys I purchased the axles, Detroit Locker, Main Cap and install kit from.
http://www.tomsdifferentials.com/
While its not a 9 inch, This package has given me years of great service.

 

[Garrett1982]

My 79 Monte Carlo has been running a GM 7.5 with a Detroit Locker, Richmond 4.10 gears, Tom's KA 28 spline axles, Summit girdle cover and a 8.5 modified steel cap on the ring gear side for over 8 years on Mickey Thompson ET Streets.
While the 406 SB Chevy and turbo 350 trans.with 3000 stall converter make less than 500 HP, this set up has performed quite well for 8.10 sec 1/8 mile passes in full street trim.
These are the guys I purchased the axles, Detroit Locker, Main Cap and install kit from.
http://www.tomsdifferentials.com/
While its not a 9 inch, This package has given me years of great service.

I couldn't find the prices on the site. I was just curious what was the total cost invested in your 7.5?