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Hi Jim, I'd like to get a quote on a custom rear for a '66 Tempest. I'm thinking of putting in an 8.5" 10-bolt with posi, 30-spline bolt-in axles and a 2.93 gearset. I'd like to have it as narrow as possible while still retaining the stock control arm mounting locations, maybe using Chevy II 12-bolt axles, if that's possible? What would the choices for a posi carrier be? I'd really want the 2.93 gears but if I had no choice but to go with 3.08's, then I think I'd opt for the True-trac unit. How much would that complete rear run me (less brakes)? I'd also need it shipped to Austin TX.

Ok well to save the most money I would just use an existing housing. There really is NO room for anything behind the backing plate but about a 1/2". Anything narrower and the shock will hit the tire and the tire will rub the inner fender well. Are you using after market wheels or stockers?

We just can not get as narrow as the chevy II axles not enough rome for the control arms. BAck spacing on the rims is the way to go here. I have a Monte ss 1971 and have 295 50 15 in the wheel well and they are like skirted rear quarters if you know the car. From the rear it appears a bit mini tubed

WE normally use the 71 72 Buick 10 bolt 8.5 for these beefed up 30 spline rears. They have bolt in axles and are great for stock looking stealth application. We build a lot of these for the Buick guys for drag racing and super street driven cars.

Posi types
True Trac, Eaton , auburn, power trax, Detroit locker... just about anything because the 8.5 is a very well supported differential.

2.93 gears are not a problem nor is 3.08

I will figure a price...The 30 spline axle trick is the expensive part. as they are MOSER custom axles. those alone are 335.00 But we can still price it out and see what you think.


What is your primary use of the car? Any reason 28 spline axles will not do? Jim

about 139.47 on shipping Jim

Hi Jim, thanks for the info. It sounds like a viable option for me. I will let you know when I'm ready to go ahead with the rear. I'd just like to have a couple of points cleared up.

Would the '72 housing you'd use need to be narrowed? Isn't the later housing a bit wider than the '66? I hear ya about the wheel backspacing, but trying to find a wheel with 5" or more of backspacing really limits the choices.

Is there a TrueTrac unit for the 2.93 gears? I thought they were only for 3.08 and up.

I wouldn't mind paying for custom axles if that's the only option, but would 30-spline axles for a '66 Chevelle 12-bolt also work? I'd prefer 30-spline axles since I'm planning on building the motor for about 550 ft-lb torque, with some track use. I guess I'd probably want aftermarket axles anyway for that much power...

That is not that much horse power... Torque and when it comes in it more worrisome for us. Buicks stock produced gobbs of torque 500 foot pounds at 2500 rpm. That is quick . Horsepower does not usually hit till up in the rpm range. 4000+ so the car is well rolling by then. See my point?

You are talking about narrowing a 1/2 inch on each side...HArdly worth the effort on a rear. 4.5 backspacing and even 5" back spacing is very common for aftermarket wheels. Camaros in the 90's used 7" backspacing. I ordered Vintage rims from Summit to get my 4.5 backspacing for my Monte and it worked great to tuck the rear wheels under the car.

REMEMBER I can build what ever you want BUT it will cost more money. Compared to the actual difference and problem your solving with this particular build ... It really will not change the look or function or the rear. JUST waste your money. NOW better money spent would be the 30 spline custom axle upgrade to the 1971 1972 housing. I can get these axles for you

Chevy axles: Chevy 12 bolt 30 spline axles will NOT work in this housing as they are c-clip axles . this 10 bolt 8.5 housing is a bolt in type axle housing.

MONEY : If money is not a problem then I would suggest a Moser housing 33 spline axles ford ends any posi choice any gear choice set up for drum or disc. Drum rear would be 2599.00 disc is 2899.00 with out brakes 2149.00

Lastly. We can help guide you in what you want to do. I am always practical in what parts are offered to the customer. I will suggest parts that will do the job NOT overly ridiculous over built parts...If you needed them I would certainly suggest the parts and or labor to chop the housing. I do make money off narrowing and axles etc. But I do build and did build muscle cars so I know what fits and works. It ultimately is your decision and we will help however you want the build done. Jim