rear diff location help??

[aany001]

This might be a stupid question but how do I know my differential is centered in my car (69 camaro). I have the DSE mini tub kit with a shortened 10 bolt and the factory perches cut off.Just would like to know where is the centre line for these diffs?? As of right know when I have the complete diff assembled with my disc brakes and 18x12 wheels installed in the car the left rear wheel is closer to the quarter lip than the right side by 3/4".From the back of the car you can really see the difference.I tried sliding the whole diff to the right approx 1/2" but I loose my gap between the left inner tire to leaf spring clearance.I have lots of space on the pass rear tire inner and outer!!! some body please shed some light on the situation!!! At least if I know that the diff is where it is supposed to be I can figure out my other clearance issues.
Thanks in advance.
Steve

[chicane67]

Factory GM pinion offset from chassis centerline is... 0.500" to the passenger side.

Factory GM pinion angle, which is set at the time the perches are welded to the tubes is... +4*.

[big gear head]

That's right, the center line of the pinion is offset 1/2 inch to the right, so the center of the pinion to the right axle flange is 1 inch shorter than the center of the pinion to the left axle flange.

[aany001]

I completely understand what you guys are telling me but where is the diff supposed to be under the car....should the pinion centreline be in the middle of my rear frame rails?

[chicane67]

It should be 0.500" closer to the passenger side framerail... if your framerails are straight that is.

[big gear head]

Actually it would be 1 inch closer to the right frame rail than the left. The 1/2 inch offset would make it 1 inch closer to the right.

[BRYANS616]

I have the same problem with my 69 firebird. I have a 2ND gen posi disc brake rearend that i am ging to weld new perches on for use in my 69. Can i weld the perches 1/4 to 1/2" off center so wheels fit better or would it cause problems???? -- bryan

[big gear head]

Place the spring perches an equal distance from the ends of the housing. This should center everything the way it is suppose to be.

[BRYANS616]

that would still place drivers side wheel much closer to the fender lip. while the pass side closer to the inner wheel tub(due to the fact the older cars are not square). If i welded the perches 1/4 inch toward the pass side the wheels woudl be more centered in the wheel wells and not rub. is this a bad idea.

[LateNight72]

that would still place drivers side wheel much closer to the fender lip. while the pass side closer to the inner wheel tub(due to the fact the older cars are not square). If i welded the perches 1/4 inch toward the pass side the wheels woudl be more centered in the wheel wells and not rub. is this a bad idea.

I am not sure why you think welding the mounts equal distance from the frame rails will cause it not to be straight?

[BRYANS616]

the distance i was refering to is the distance from the housing ends not the frame rails. the problem is with my wheels/tires the drivers side is very close to outer lip while the pass side rubs the inside a bit. the the 2nd gen rear i a want to use is 1/2" wider. 1/4 per side. i have to weld perches in the correct spot for my 1st gen. wondered if placed them 1/4 to 1/2" toward the pass side this would move the rear over getting the drivers side clear of the fener lip and not rub the inside on the pass side. instead of cutting fender lip on one side and adding a spacer on the other.

[big gear head]

Why is your car so far off? I think you need to figure out why it is off and fix the problem. The spring bushings or something else is wrong.

[BRYANS616]

I assumed this was common. In Tony h. pro touring book in the fitting wheels and tires section he said he has seen as much as 7/8" differance side to side. because the factory doesnt build square cars.(60s and 70s cars). I dont know this is my first endevor.