12 Bolt Rear End Question

[Malcolm7]

I am new to Monza restoration, but owned an original 1978 back in the day.

Recently I purchased a rust free 1980 Monza 2+2 which which the last owner started to convert into a drag race car.

It has a 12 bolt rear end installed - which is the source of my questions.

The width measurement flange to flange (without brake rotors) is 60 inches - far wider than the stock Monza rear end. Each side appears to have two 1 inch spacers behind the flanges. The front end has a 5 lug conversion - which looks to be near to the standard width.

1. Will this rear end width make handling (cornering) difficult?

2. Is there a practical way to reduce the rear width, or is it better to swap the 12 bolt out for a narrower and smaller axle?

3. Are there other options?

I do not intend to turn this car into a mega HP monster. 300HP max is all that I am interested in.

Any useful input will be much appreciated.

[Smiley]

the "spacers" are probably C clip eliminators.
does it have ladder bars ?
you could use deep backspace wheels or have the 12 bolt narrowed to use the wheels you choose.
Late Corvette and Camaro wheels may work, Weld wheels have a good selection of backspacing options.
Pics would help.

[dadhad1]

Do you have std C clips or bolt in axles?
I'd say, if the rearend is good (right ratio for you, not leaking, not whining), change the oil and stay with it.
A 12 bolt is a strong strong street rearend, especially for 300 hp.
You can likely get the wheel offset needed to get the tires where you want them.

[Malcolm7]

Thanks for the feedback.

The car does not have ladders. The last owner welded in upper connectors to use four link rear suspension vs. torque arm for some reason.

The axle is not yet hooked up to the driveshaft, and no rear shocks are installed. The car is just a roller. I do not know the internal condition of the axle.

Here are a few photos. Are the yellow blocks some sort of spacer? Each is 1 inch thick.

I live in the Detroit area. Hopefully I can find a shop here that can do any needed work.

[Malcolm7]

SORRY - HERE ARE THE PHOTOS:

[Monza Harry]

Malcolm7 these guy's have a real good reputation I will probably be going there soon but I haven't yet so I only have Internet gossip to go by Harry http://www.ccidriveline.com/

[Smiley]

Those are c clip eliminators, but it appears to have stock axles.

[Malcolm7]

Harry and Smiley - Thank you both for the responses. I will attempt to work with this axle.

[chevyart]

you cant shorten and respline stock GM 12 bolt axles. shafts are parallel and too narow to do that. art

[Malcolm7]

I assume that shorter 12 bolt axles are available?

[chevyart]

for sure they are available. curry enterprises and mosier are the 2 main suppliers and innovators of rear end parts. art

[Wizeguyrc]

There are also two different bearing styles. Most of the time the drag race version of c-clip eliminators has a cage style bearing that will not hold up for street use.
I added the oval track style c-clip eliminators to my 12 bolt, in the Chevelle, when I ordered my axles from Strange Engineering.

They also offer a 12 bolt/GM style housing end that accepts a 3.150 Ford bearing. Going this route will let you keep your GM brakes and get rid of the c-clip eliminators. If you find you have the cage type bearings, are going to cut the housing and have to order new axles, this may be a way to go.

Here is a link to their online catalog: http://www.strangeengineering.net/index.html

[chevyart]

real good info tracy art

[monzaz]

Ok here are some things we can see. You have camaro factory disc brake brackets... the c-clip elim kit is probably Strange as they are 2 piece blocks.
Moser is a one piece block c-clip elim system Which I prefer for my builds.

Now if this rear is wider there is probably a good reason for keeping it this way. The disc brakes can only be used on a Monza / 75-80 H-body car with wider over all axle as the disc brake caliper needs to be mounted on the flange of the axle housing outside of the inner fender well . If you had it stock width the caliper WILL hit the fender well and can not be used. SO... if you want to keep the disc brake option leave it alone and get the off set backspace rims to use the disc brakes. You will probably need about 5.5 -6' negative backspacing on the rims to do the job and keep them under the car.

Axle shaft cut and respline - BAD IDEA...No one does this anymore to a stock axle. It makes NO sense since the stock GM axle is - too weak, case hardened (means only the outer 1/16" at the most is hardened) - Metal mix is inferior and the axle is a tapered axle meaning you will NOT get enough diameter until the axle IS NARROWED TO ABOUT HALF THE ORIGINAL LENGTH.

All in all either use this axle as is...Or just build up a stock rear for 300 HP Some 28 spline axles and 28 spline posi good aftermarker gears and your stock 7.5 rear will handle 300HP easy.

Jim
J D Race

[Malcolm7]

Jim,

Thank you for the clarification points about the brakes and width. I do plan to use disk brakes.

This is probably a much larger rear axle than I need for a mild street rod, but the easiest option many be to use as is.

Someone spent a great deal of effort converting this car over to a four link vs. torque arm suspension - which may not be as good for handling.