Toms 12 Bolt Diff Conversion
Thread Starter
Instructor
Joined: Mar 2011
Posts: 115
Likes: 1
From: Victor Harbor SA
Toms 12 Bolt Diff Conversion
Down the track... Looking at maybe changing out my stock 3.08 rear for a 3.55 Toms 12 Bolt.
A few on this forum have already done this conversion.
Anyone like to give a 'Rough' guide on full cost of change over ?
I'm talking from wheel-to-wheel. The whole lot. Car is a 68.
Cheers.
A few on this forum have already done this conversion.
Anyone like to give a 'Rough' guide on full cost of change over ?
I'm talking from wheel-to-wheel. The whole lot. Car is a 68.
Cheers.
Race Director
Joined: Jan 2000
Posts: 13,015
Likes: 2,260
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Until they get the new case developed that they've been working on forever...the highest you're going to get is 3.73's with all 12 bolt guts.
There's a "Super 10" version that does some mixing and matching and does very well unless you have insane power and traction.
CK with Mike...Traccdog here on the Forum.
JIM
There's a "Super 10" version that does some mixing and matching and does very well unless you have insane power and traction.
CK with Mike...Traccdog here on the Forum.
JIM
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas
Like Jim said the tallest gear you can get is 3.73 in the 12 bolt. The Super 10 can be built with any ratio. The main difference between the two is carrier strength. Being down under, replacement parts and shipping expense also needs to be factored in. Spending more up front can end up costing less in the long run.
There are so many options it's hard to give even a rough estimate. 1480 u-joints cost more up front but will last much longer than 1350's. Stock or offset traing arms? Which brand? I'll send you a pm with my info so we can discuss this in detail.
Mike
There are so many options it's hard to give even a rough estimate. 1480 u-joints cost more up front but will last much longer than 1350's. Stock or offset traing arms? Which brand? I'll send you a pm with my info so we can discuss this in detail.
Mike
Cruising
Joined: Aug 2013
Posts: 11
Likes: 0
I called vansteel and went through this with them on my 69 im building . told them im getting a big block with about 630 hp.so what do you recommend fore the rear. they did a quick figure on rear wheel hp witch put it at about 500 or so,and said going with the 31 spline axles , iner and outer, $1,700 30 spline spider gears $290,and 75-79year half shafts $400 and of course rebuilding the rear,cluches,411 gears and so on. on my 10 bolt. So im in over 3,000, but half the price of a 12 bolt. I also told them that this is a street car and wouldent be going to the track. Just another possible option,dont know how much hp you have good luck Brad
Bud2
Joined: Jul 2005
Posts: 1,237
Likes: 4
From: Warrnambool Victoria
G'day Luke,
I had Gary build my Super 10 bolt back in 2011. I've got 530 trying to rotate my 275 MT tyres. The diff cost me about 3500 A$ to get to Melb. All reports point out that Mike and Gary are both top notch with their diffs. The rest of the parts are listed through Tom's site or Vansteel. In my opinion, I'd rush! Don't think the Aussie dollar will stay as strong as it is at the moment. I've ordered all new interior and a Keisler 5 speed for next years projects.
Hey, on another matter, we're having a big Corvette only show down here in Warrnambool, Vic. Good prizes! Jan 26. Bring a CONVOY down to it if you're free.
Bud.
I had Gary build my Super 10 bolt back in 2011. I've got 530 trying to rotate my 275 MT tyres. The diff cost me about 3500 A$ to get to Melb. All reports point out that Mike and Gary are both top notch with their diffs. The rest of the parts are listed through Tom's site or Vansteel. In my opinion, I'd rush! Don't think the Aussie dollar will stay as strong as it is at the moment. I've ordered all new interior and a Keisler 5 speed for next years projects.
Hey, on another matter, we're having a big Corvette only show down here in Warrnambool, Vic. Good prizes! Jan 26. Bring a CONVOY down to it if you're free.
Bud.
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Pro
Joined: May 2013
Posts: 672
Likes: 31
From: Rapid City South Dakota
Down the track... Looking at maybe changing out my stock 3.08 rear for a 3.55 Toms 12 Bolt.
A few on this forum have already done this conversion.
Anyone like to give a 'Rough' guide on full cost of change over ?
I'm talking from wheel-to-wheel. The whole lot. Car is a 68.
Cheers.
A few on this forum have already done this conversion.
Anyone like to give a 'Rough' guide on full cost of change over ?
I'm talking from wheel-to-wheel. The whole lot. Car is a 68.
Cheers.
The only gear ratios for a Tom's 12 bolt are 3.73, 4.11 and 4.56 because a bigger ring gear won't fit in the case.
6800 for the 1480 kit, 6300 for a 1350 kit, doesn't include trailing arm rebuild.
I've got a brand new Toms 12 bolt 3.73 still in the crate in my garage if you're interested. It's for a 1350 axle kit, and I have the receipt.
Advanced
Joined: Dec 2010
Posts: 69
Likes: 1
From: Chios Chios
I just did a similar installation in my 69. You need to decide if you want a 1480 vs 1350 axle kit for starters. The 1480 involves cutting the battery box and other fiberglass areas to make room for the u joints.
The only gear ratios for a Tom's 12 bolt are 3.73, 4.11 and 4.56 because a bigger ring gear won't fit in the case.
6800 for the 1480 kit, 6300 for a 1350 kit, doesn't include trailing arm rebuild.
I've got a brand new Toms 12 bolt 3.73 still in the crate in my garage if you're interested. It's for a 1350 axle kit, and I have the receipt.
The only gear ratios for a Tom's 12 bolt are 3.73, 4.11 and 4.56 because a bigger ring gear won't fit in the case.
6800 for the 1480 kit, 6300 for a 1350 kit, doesn't include trailing arm rebuild.
I've got a brand new Toms 12 bolt 3.73 still in the crate in my garage if you're interested. It's for a 1350 axle kit, and I have the receipt.
Pro
Joined: May 2013
Posts: 672
Likes: 31
From: Rapid City South Dakota
I've got the complete differential. It's got the 30 spline heavy duty stub axles, and of course this needs the heavy duty spider gears. The 12 bolt ring and pinion will only work on the 12 bolt posi units, which are stronger and thicker. The 10 bolts tend to crack and wear the cross shaft hole bigger, depending on application of course. It's set up for the 1350 u joint kit, I also have some new Van Steel trailing arms and Dick Gulstrand trailing arms with 31 spline spindles.
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
I built a Super 10 for my 75. I used the 30 spline stub axles and spider gears, Richmond 4.11 gears, larger cross shaft, polished the posi case, and put the steel bearing cap on with larger bolts. I bought 3.5" Denny's Nitrous Ready half shafts and used Tom's spindles in VB&P offset trailing arms.
I set the posi up per Tom and Gary's spring-less method, but I'm still a little wierded out by that. I've built plenty of differentials, but never without springs.
I've got my motor, trans, drive shaft, and full rear drive and suspension ready to go, but none of it in the car yet. I'm anxious to try it!
I set the posi up per Tom and Gary's spring-less method, but I'm still a little wierded out by that. I've built plenty of differentials, but never without springs.
I've got my motor, trans, drive shaft, and full rear drive and suspension ready to go, but none of it in the car yet. I'm anxious to try it!
Last edited by v2racing; Dec 29, 2013 at 03:51 PM.
Advanced
Joined: Dec 2010
Posts: 69
Likes: 1
From: Chios Chios
I've got the complete differential. It's got the 30 spline heavy duty stub axles, and of course this needs the heavy duty spider gears. The 12 bolt ring and pinion will only work on the 12 bolt posi units, which are stronger and thicker. The 10 bolts tend to crack and wear the cross shaft hole bigger, depending on application of course. It's set up for the 1350 u joint kit, I also have some new Van Steel trailing arms and Dick Gulstrand trailing arms with 31 spline spindles.
Thank you.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I built a Super 10 for my 75. I used the 30 spline stub axles and spider gears, Richmond 4.11 gears, larger cross shaft, polished the posi case, and put the steel bearing cap on with larger bolts. I bought 3.5" Denny's Nitrous Ready half shafts and used Tom's spindles in VB&P offset trailing arms.
I set the posi up per Tom and Gary's spring-less method, but I'm still a little wierded out by that. I've built plenty of differentials, but never without springs.
I've got my motor, trans, drive shaft, and full rear drive and suspension ready to go, but none of it in the car yet. I'm anxious to try it!
I set the posi up per Tom and Gary's spring-less method, but I'm still a little wierded out by that. I've built plenty of differentials, but never without springs.
I've got my motor, trans, drive shaft, and full rear drive and suspension ready to go, but none of it in the car yet. I'm anxious to try it!
My stock original 79 yokes wore away in less than 50K miles past the C clips destroying the rear end. I bought back in the 80's a built up Tom's rear end with 17 spline hardend yokes from Mid America. I failed some posi units with broken cases and finally bought the Tom's stage 7 posi units. They were the polished units with a bigger pin. I put together another rear end with my 4.11 gears and extra steels to make the rear end super posi because it is so tight. It still has springs. Gary builds really nice stuff
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
Holy late reply George! Five years?
Well I've got some miles on this setup and it works great. F1 Supercar tires rarely hook solid, so not the same as track tested though. I was a little apprehensive about running no posi springs, but I have to say you step on it and both tires spin and it goes straight every time with none of the clunking around corners you can get with the springs. I'm happy.
Mike
Well I've got some miles on this setup and it works great. F1 Supercar tires rarely hook solid, so not the same as track tested though. I was a little apprehensive about running no posi springs, but I have to say you step on it and both tires spin and it goes straight every time with none of the clunking around corners you can get with the springs. I'm happy.
Mike