4th Gen Rearend

[CMcAllister]

Typically, one sources the wheels to be used with the desired BS that will be used, throws a set of the largest (or desired size) tires that will be used on them. With no rear in the car, position them under the car in the desired location, measure wheel flange to wheel flange and build the rear to that dimension taking into consideration the brake kit being used, pinion offset, etc. Build the rear to wheels - not the other way around. Typically.

Enough of those cars out there, the dimensions and specs should be standardized with little need to figure it all out yourself.

[kansas stocker]

I was told it needed to be within 1/4" of stock.
Guess it depends on who you ask.
Pete

[2021STK]

for some, asking forgiveness is easier than asking permission.

[mtwilly]

Thank you again for the help. I do not have the wheels and tires yet as I wanted to verify I was going to be legal on the width first. Will be running a 28x9 slick initially on a 9 or 10" wheel and possibly switch to a 30x9 down the road. From what I can gather (haven't measured mine, yet) the stock width is 64.72". It seems the general consensus is that rear end width is less important (within reason) than the the fact that the suspension and wheel housings are in their factory place. I really just want the mounting surface of the wheel as close to center as possible. Thanks again for all your input! So much to learn about class racing but enjoying it so far!

[CMcAllister]

Deeper wheel = shorter rear = less unsprung weight. I realize there's not a lot to be gained with a 9 or 10 in. wheel, but every little bit counts. And they don't charge extra for deeper wheels or shorter axles.

[Mike Mans]

Here's my question: The rule says it must be a stock width rear end with all of the details everyone has outlined. I've searched the classification guide high and low and I can't find anywhere that they note just what a stock width rear end should be for every car in competition. Anyone able to point me to that? If it's not documented in the NHRA classification guides at this point - it seems like a pretty unenforceable rule.

[Michael K]

Classification guide won't have this info.


The rule book talks about wheel base. Since there are production line assembly tolerances, there is an allowable variation from factory specifications (I can't recall exactly...3/4 inch?). The rear axle width is not addressed, other than stock mounting points and stock width (between backing plates) must be used. I have factory rear housings that vary up to 5/16 inch for the same model of car.


In the spirit of the rules, it would seem that the factory tolerances should be factored in within reason. When asked, division tech would only say that they would not allow stock mounting points to be moved.

[Rob Petrie E395]

Since no one posted it. On a 4 gen F body. If you have a stock length rear end. Using a 10 inch wide wheel you need 7 1/2 inches of back space.

[mannymen]

The trick is to use an 82-92 F-Body “STOCK WIDTH” rearend. It’s a complete bolt-in for a 93-02 F Body. The 82-92 is approximately 4” shorter than a 93-02 rearend. This is what u r seeing in the pics u posted. Now you can use a 15x10 wheel with a more common 5.5 backspace.

[Greg Reimer 7376]

Where in the world is there a spec list or a source of published information regarding rear end housing widths? Nobody I know even mentions ever having been checked. Wheelbase, yes, but housing widths? If you put a 66 stock width Impala rear end in a Camaro with leaf spring perches installed, I'm sure that wouldn't fly with the extreme width differences, unless the big car rear end was narrowed, but I've never seen a spec for any car's mandated rear end width. With all the fourth gen F body cars out there, it should be no problem finding a good one all ready to go, in fact, don't the established rear end shops offer a complete ready to use rear end that's a bolt in?