Prepped 10-bolt vs 9-bolt
Thread Starter
Joined: Jul 2007
Posts: 358
Likes: 2
From: Waukesha, WI
Car: 86 Camaro Z28
Engine: LT1 200cc Ai heads and cam
Transmission: T56
Axle/Gears: 4.10:1 Zexel Torsen
Prepped 10-bolt vs 9-bolt
Please don't start off with, "Just put a 9" in it". This is for me to determine if it's worth it to switch over to a 9-bolt, or is the difference negligible. Currently, I have about 450HP to the wheels. My goal is to do recreational auto-x and possible road course driving and not really drag racing. My concerns are weight, power drain, factory torque arm attachment, and budget.
Current Setup:
Current Setup:
- 2002 Z28 axle
- Zexel-Torsen differential
- 4.10:1 ratio
- Welded axle tubes
- Cover girdle
- Solid pinion spacer <- forgot to add this
- Similarly setup, will it be stronger?
- I would be adding a helical gear differential, instead of the original cone setup
- What is the difference in weight?
Last edited by diablizzard; Feb 3, 2024 at 08:40 AM.
Joined: Oct 2001
Posts: 12,214
Likes: 1,140
From: Il
Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Prepped 10-bolt vs 9-bolt
The problem you'll have in a 10bolt with 373/410 and deeper gears is that the pinion gets small and doesn't share the load with as many teeth. They tend to break teeth and pinion heads off.
iirc, they are close enough to the same weight not to worry about that. id use the 9bolt with upgraded diff because of the bolt in axles, no c-clips like the 10bolt.
iirc, they are close enough to the same weight not to worry about that. id use the 9bolt with upgraded diff because of the bolt in axles, no c-clips like the 10bolt.
Junior Member
Joined: Oct 2023
Posts: 44
Likes: 44
From: Indiana
Car: 1988 Pontiac Formula Firebird
Engine: None
Transmission: None
Re: Prepped 10-bolt vs 9-bolt
Please don't start off with, "Just put a 9" in it". This is for me to determine if it's worth it to switch over to a 9-bolt, or is the difference negligible. Currently, I have about 450HP to the wheels. My goal is to do recreational auto-x and possible road course driving and not really drag racing. My concerns are weight, power drain, factory torque arm attachment, and budget.
Current Setup:
Current Setup:
- 2002 Z28 axle
- Zexel-Torsen differential
- 4.10:1 ratio
- Welded axle tubes
- Cover girdle
- Similarly setup, will it be stronger?
- I would be adding a helical gear differential, instead of the original cone setup
- What is the difference in weight?
Last edited by rhyno91; Feb 3, 2024 at 04:50 AM. Reason: Clarity
Thread Starter
Joined: Jul 2007
Posts: 358
Likes: 2
From: Waukesha, WI
Car: 86 Camaro Z28
Engine: LT1 200cc Ai heads and cam
Transmission: T56
Axle/Gears: 4.10:1 Zexel Torsen
Re: Prepped 10-bolt vs 9-bolt
There are helical gears available, but all the companies I found so far are in Australia. The search I used was for M78. Mace Engineering diffs can be find in eBay. There are at least 2 more manufacturers I've found, but I'm out of town for the weekend. I can post up the links I find when I get home. I haven't emailed anyone to figure out model fitment, yet.
Mace M78 search
Mace M78 search
Thread Starter
Joined: Jul 2007
Posts: 358
Likes: 2
From: Waukesha, WI
Car: 86 Camaro Z28
Engine: LT1 200cc Ai heads and cam
Transmission: T56
Axle/Gears: 4.10:1 Zexel Torsen
Re: Prepped 10-bolt vs 9-bolt
The problem you'll have in a 10bolt with 373/410 and deeper gears is that the pinion gets small and doesn't share the load with as many teeth. They tend to break teeth and pinion heads off.
iirc, they are close enough to the same weight not to worry about that. id use the 9bolt with upgraded diff because of the bolt in axles, no c-clips like the 10bolt.
iirc, they are close enough to the same weight not to worry about that. id use the 9bolt with upgraded diff because of the bolt in axles, no c-clips like the 10bolt.
Will the slightly larger gear in the 9-bolt help with the pinion issue? That also sounds like a problem with the case flexing a little bit.
Junior Member
Joined: Oct 2023
Posts: 44
Likes: 44
From: Indiana
Car: 1988 Pontiac Formula Firebird
Engine: None
Transmission: None
Re: Prepped 10-bolt vs 9-bolt
There are helical gears available, but all the companies I found so far are in Australia. The search I used was for M78. Mace Engineering diffs can be find in eBay. There are at least 2 more manufacturers I've found, but I'm out of town for the weekend. I can post up the links I find when I get home. I haven't emailed anyone to figure out model fitment, yet.
Mace M78 search
Mace M78 search
Good luck with your build, no matter what you end up going with.
Junior Member
iTrader: (3)
Joined: Aug 2021
Posts: 75
Likes: 30
Car: 89 GTA
Engine: 350
Transmission: auto
Axle/Gears: 3.23 BW 9 bolt
Re: Prepped 10-bolt vs 9-bolt
9bolt.com, located in Australia, is were I got my new carrier for my 9 bolt. It just cleared customs and I should have it by next week hopefully. It was about $595 shipped
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Supreme Member
Joined: Jan 2004
Posts: 2,322
Likes: 100
From: So. Ohio
Car: 88 Camaro
Engine: L98 350
Transmission: 700r4
Re: Prepped 10-bolt vs 9-bolt
I could be off here but I don't see any real difference in /strength between either of them. The standard 10 bolt with the 8.5 ring vs the 9 bolt 7.75" in a better housing. A solid built 10 bolt is not weak garbage.
Joined: Aug 2015
Posts: 196
Likes: 11
From: Salt Lake City. UT
Car: '92 RS
Engine: 5.0TBI
Transmission: TKX
Axle/Gears: 2.73
Re: Prepped 10-bolt vs 9-bolt
Well for one thing, the 10 bolt that comes with third gen's has the 7.5 inch ring gear and that rear is weaker than the 8.5's.
Thread Starter
Joined: Jul 2007
Posts: 358
Likes: 2
From: Waukesha, WI
Car: 86 Camaro Z28
Engine: LT1 200cc Ai heads and cam
Transmission: T56
Axle/Gears: 4.10:1 Zexel Torsen
Re: Prepped 10-bolt vs 9-bolt
I probably should have clarified the 10-bolt is the 7.5".
Joined: Oct 2001
Posts: 12,214
Likes: 1,140
From: Il
Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Prepped 10-bolt vs 9-bolt
as others have said, the 10bolt in 3rdgens is 7.5 or 7.625. The 8.5 was a 2nd gen thing and much stronger than the 3rds
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