Help Spec'ing a Rearend

[JMarsa]

What's more better? I want a to build a reasonably priced rearend that's bullet-proof for my circumstances. I have neither an all out car nor budget.

I'm comparing mainly two alternatives for my ~420 RWHP LS6 powered, T-56 shifted 3200 lb Nova, AutoX, HPDE, street car with 295 series DR/sticky tires. The car might see 6-10 1/4 mi passes when it's done just to get times. I'm not into drag racing. Both will use a C5/6 rear brake set-up.

1. 8.5" 10 bolt from a Caprice
This will require new 3.90 gears, a diff and axles since the caprice is 5x5. I'm thinking a Truetrac for this set-up.

2. 9" from a truck
Do I need Torino big bearings? This will also require 3.90 gears, new axles (5x4.75) and a diff - I'm thinking Platinum Trac or Black Gold.

3. 8.8" any $$ savings over a 9" when everything has to be spec'd ??

I'd like to keep the whole package (minus brakes) around $1500.

BTW, I'm running a wide rearend due to Vette zero offset wheels.

--JMarsa

[big gear head]

How wide? I have some Nova 8.5 rear ends that I can build for around that price.

Here is what I would do. I'd use the 8.5 GM rear end. It's lighter than the 9 inch and plenty strong for what you want when it is built right. I'd use a 30 spline Truetrac with 30 spline Moser axles. As for axle bearings, you have some choices. You can stay with c clip axles, which are pretty good in most cases. You can also use the Moser housing ends with the press on tapered roller bearings. These eliminate the c clips and help with side loads. The cost is higher, but the bearings are better. I've installed several sets of the ends and they work great. You can use GM brakes or any of the brakes that are avaiable for the 9 inch Ford. An 8.5 truck housing could be narrowed to the width that you need to fit your wheels exactly where you want them.

[JMarsa]

Thanks for the reply. The car already has a 8.5 10 bolt which is approximately 3" too narrow per side for the wheels I'm using.

Given the cost of a used housing, new gears, new axles and a new diff I think I can build either for about the same price.

I really don't want to have to rethink my wheel plans since I already have them.

--JMarsa

[big gear head]

If you give me the overall width of the rear end that you are using with the spacers installed I can build a rear end that will fit without using the spacers. I'd be using a truck housing because they are wider and can be cut to size. what about the axle bearings? Do you want to keep the c clips or use the press on tapered roller bearings?

You could sell that Nova 8.5 to someone with a first gen Camaro. They are pretty popular with those guys.

[JMarsa]

If a truck rear is narrowed what are my options for new housing ends? You mentioned Moser housing ends with the press on tapered roller bearings are there other choices?

If I go with the Moser ends, how does it affect the type of axle I need (I'm thinking profile for the new bearing type)? I will need 5 x 4.75 bolt pattern.

Do those ends allow you to eliminate the broken axle concern that c-clips have? With rear disks shouldn't be a concern anyway right?

--JMarsa

[big gear head]

There are several housing ends that can be used. If you want to keep the c clip axles then I would use a set of stock car housing ends. You can use any GM car brakes with this. If you want to use the tapered roller bearings then there are 2 choices. Moser makes a housing end for these bearings that has the GM car bolt pattern so that GM brakes can be used. They also make these ends with several of the Ford bolt patterns so that the popular 9 inch and other Ford and after market brakes can be used. There are also sealed ball bearings for these housing ends, but the tapered rollers handle the side loads better.

The press on bearings do eliminate the concern of loosing an axle and wheel if the axle breaks. Disc brakes are not always enough to retain the axle if it breaks. I work with a guy who raced on an asphalt oval. He had c clip axles and disc brakes. He broke an axle and the wheel and axle came out. It hit the fence and killed a guy who was standing too close to the other side.

The type of brakes being used will determine the hang out on the axles. The stock GM hang out is 2 3/4 inches. Ford uses 2 1/2 inches. The axles would be made to fit the brakes that you use, and the housing would have to be built for the correct axle hang out, with the right bolt pattern on the housing ends. As for the bolt pattern on the axles, it will be 5 on 4 3/4. I usually order the axles drilled for press in and screw in studs.

[JMarsa]

Thanks again for your replies.

I'll be using C5/C6 'vette rear brakes. I don't have them mounted yet but will be using the Kore3 mounting plates.

Thanks for the info. Let me get some measurements this weekend and I'll post a reply.

--JMarsa

[big gear head]

Just to let you know up front, if you use the press on bearings and the GM brakes then the caliper bracket will need to be slightly modified. The caliper bracket acts as the axle retainer. It will need a .125 deep counter bore on the back side for bearing clearance.

[JMarsa]

Thanks. I saw a reference to that on their website:



Note: Axle flanges must be less than Ø6" outside diameter to properly mate with rotors. Most OE axle shafts will need to be modified.--JMarsa