Rear sub-frame and diff questions.

[NavySupra]

Unfortuantly I had to choose between my supra and my grandpa's car. My grandpa's car won.

This is a project of a huge scale, at least it seems that way in the planning phases. I have a 1956 Chevy Bel-Air convertable that I'm converting to a LBZ duramax (350hp, 650ft.lbs) and will be using the 6 speed Allison automatic.

Extensive modifications to the chassis will be needed to fit this combination in the car. My current plan is to use the mkIII rear subframe and obviously the IRS. I want to go twin turbo to get the right exhaust note, so I wouldn't mind turning it up a little.

My question is, in your opinion what is the maximum torque the diff and axels can take? I'm hoping to keep the total vehicle weight under 5500lbs but I don't know if that is possible or what the weight balance will be.

 

[IJ.]

Never heard of a Mk3 axle breaking.

On my last engine I was making 1154 Nm of torque and never tore up a G series diff.

Short of a balls to the wall drag launch on sticky tires I don't think you'll have an issue.

 

[jawsgear]

Wait so you want to put the supra subframe and diff in the Bel Air???????:nono:

 

[NavySupra]

Wait so you want to put the supra subframe and diff in the Bel Air???????:nono:

That is correct along with a turbodiesel v8. New suspension up front, though I have to fit the dmax before I decide what. Disc brakes all around.

The track width stock on the mkIII is within a single milimeter of the stock chevy diff. Lots of room to fit wide wheels in there

 

[jawsgear]

That is correct along with a turbodiesel v8. New suspension up front, though I have to fit the dmax before I decide what. Disc brakes all around.

The track width stock on the mkIII is within a single milimeter of the stock chevy diff. Lots of room to fit wide wheels in there

No offense but that has got to be the dumbest idea I have ever heard of. By the time you mod that shit to fit in there you could have a real nice differential in there like a 12 bolt or a 9". AND it will also hold up to the abuse this car is obviously gonna see with that motor and trans combo.

Jeff

 

[BorHor]

^ GO DIFF MASTER GO!!

Just wondering.. but why do you want to use Mk3 rear sub frame, and also will it be worth the hassle?

 

[NavySupra]

Major reason I want to use it, is because I have a complete subframe laying around. Anyone can bolt in a 12 bolt with discs, or buy a ford 9" kit for the 56.

Mostly I need the challenge, I put a 12valve cummins in my ford and that turned out to be pretty easy.

 

[figgie]

how is that subframe looking though?

Might want to reinforce any part of the subframe that is looking weak. With the age it will be too!

As for the MKIII diff. As IJ. stated. I have not heard of anyone grenading the rear end of this car. The torsen based diff yes but the clutch pack one. Nope.

 

[NavySupra]

how is that subframe looking though?

Might want to reinforce any part of the subframe that is looking weak. With the age it will be too!

As for the MKIII diff. As IJ. stated. I have not heard of anyone grenading the rear end of this car. The torsen based diff yes but the clutch pack one. Nope.

Yes the subframe will be massively reinforced to support the extra weight and torque. The diff will be rebuilt as well to be on the safe side. I think it's a 3.53 right now but I might try and get something closer to 3.

I'm shooting for 500hp, 1000ft.lbs though might push it to 1200

 

[figgie]

Yes the subframe will be massively reinforced to support the extra weight and torque. The diff will be rebuilt as well to be on the safe side. I think it's a 3.53 right now but I might try and get something closer to 3.

I'm shooting for 500hp, 1000ft.lbs though might push it to 1200

Can not be a 3.53

supra's never came with that.

it was either

4.1 (N/A)
3.9 (Turbo up to 88)
3.7 (89+ turbo)

3.5 Only came in the Toyota 4 Runner and I have not heard of anyone doing a successful swap as of yet.

So tread new ground and do the swap!

 

[jawsgear]

Yes the subframe will be massively reinforced to support the extra weight and torque. The diff will be rebuilt as well to be on the safe side. I think it's a 3.53 right now but I might try and get something closer to 3.

I'm shooting for 500hp, 1000ft.lbs though might push it to 1200

I doubt it is a 3.53 ratio. Show me what MK3 has ever had a diesel motor with an allison trans behind it and lets see how long that diff held up. hahahaha:biglaugh:

 

[figgie]

I doubt it is a 3.53 ratio. Show me what MK3 has ever had a diesel motor with an allison trans behind it and lets see how long that diff held up. hahahaha:biglaugh:

weakest link will be the first to go.

at that power level.

Smoke show for the tires.

Change them to slicks.

Thrust washer in the R154 is next.

after that, the driveshaft and one that is addressed. Perhaps then, will the diff give the ghost up. On street tires. All smoke.

 

[NavySupra]

I doubt it is a 3.53 ratio. Show me what MK3 has ever had a diesel motor with an allison trans behind it and lets see how long that diff held up. hahahaha:biglaugh:

I don't always know the correct numbers and terms.

Well in about 4 to 5 years when the car is complete I'll find out the limits! I'm going to try and keep the tires as the weak link. 255 to 275ish wide. Something that will brake loose and make lots of smoke.

Primary roll as a road trip car, but some drag racing and dyno pulls. Might even try road coarses if the car ends up really stable.