Swapping the Rear End

I will be mounting the axle in the next couple weeks and one of the details I will be checking is the pinion angle of the differential. It should be 3 degrees. I don't know if the pinion angle has been built into the Camaro diff's mounting plates or if I'll have to machine a 3 deg slope into the the lowering blocks. I'll just put it together and find out.

The way I understand it is that you are setting up the universal joint angles on the driveshaft. The rear-end pinion shaft should be pointing up at 3 degrees or less (measure from the flat on the top of the pinion). The tranny output shaft should point down at 3 degrees or less (measure at the engine). This means that the angle that the engine sits at is critical too!

The two angles should be equal to cancel vibration and not share a common centerline (don't point directly at each other). This is when the car is at normal weight and resting on the tires. The whole point is to minimize the vibration caused by engine power running through the universal joints. As smooth rotating power exits the tranny, it is converted to pulsating power through the driveshaft's forward u-joint, this pulsating power is converted back to smooth rotating power through the driveshaft's rear u-joint. If the angle is the same then the pulses (which we feel as vibration) cancel.

There is a few things that I have to do before I can install the differential. First I'm cleaning up the leaf springs, painting them and installing button sliders. Interestingly, I've found that standard multileaf trailer springs are 1 3/4" wide also. You can purchase them in different lengths and weights from 1000 to 3500 lbs ratings. The nice part is that they go for about $25 per side. Could be a cheap source for leaf springs!.

The differential is going to be cleaned up and painted next. All of this takes time which is something I always seem to be short of...

Rough Axle

Here's the rusty rear end right after being pulled from the Camaro

Clean axle

A little wirebrushing and paint - looks new!

Front spring bushing

Front spring bushing and bolts, notice the aluminum painted springs - oooh!

Center spring mounts

Lowering block and custom shock mount

Rear shackles

Rear shackles and bushings

The front spring bushing costs about $21 Cdn each and was bought through the local spring manufacturer. The rear shackle bushings are about $2 each and are just a generic part. You need to know the spring width (1 3/4"), inner diameter and outer diameter. I bought 1 3/4" diameter sliders and drilled holes in the springs to mount them. There were already rectangular sliders mounted that had worn out several decades ago. I had to glue the sliders in place to keep them from falling out when I put the springs back together. All it took was a little muscle and a few C clamps - not the difficulty that I had envisionned.

I was going to purchase new shackles as the original ones were rusted. The local spring shop said that if the shackle bolts were going into steel sleeves than it would be a problem but since they are going into rubber bushings, the rust disfingeration wouldn't make any difference. So in they went.

How's the fit?

The completed assembly bolted in perfectly. The Camaro rear end has the exact same mounting dimensions as the 54. Here's two vehicles 22 years apart and the widths are identical - talk about luck!

axle-spring centered

Here's the fit with the lowering blocks centered axle and spring

axle-spring offset

Axle set back 1 1/2" from spring

The lowering blocks were adjusted to set the axle back towards the rear by 1 1/2" to center (front/rear) the wheels in the wheel wells. The springs haven't had any load on them since rebuilding and I expect that they will flatten out once the engine is in and the vehicle goes for a ride. Should drop in height also.

I am running wide (9" tread) P255-60R15 wheels on stock Camaro mags on the rear. They just fit in the wheel wells. There is 3/4" clearance between the Fender lip and the tire on the outside. On the inside there is 1 3/4" clearance between the tire and the wheel well/frame. A mag with a negative offset of 1/2" less than the stock Camaro mags would center the tire perfectly at 1 1/4" inside and outside. Ideally, there should be 1 1/2" clearance on both sides but 1 1/4" should do.

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Copyright April, 2011 Eugene Blanchard