Rear end not centered to car

[selfish1]

The rear Differential in my 69 is off center to the car by 3/4" Anyone have a clue how to center this thing? thanks in advance.

 

[mike weyman]

was it wrecked or something at one time?? or was someone doing donuts on the pavement??
my guess is that the trailing arms are bent (pretty much has to be) the bolts on the springs may be bent too. shocks are probably not bent but could be.
could be rotted metal?? (forgive me but i live by the ocean)
get it up so you can see and go over evrything with a measure tape back and forth to compare.(start with trailing arms).

 

[Vettehead Mikey]

You're sure it's not the body that's offset on the frame? That's very common on these cars.

 

[GTR1999]

The differential is bolted to the rear crossmember,which is located to the frame on each end. There would have to be a pretty good load on it to offset it.If it was removed in the past there may be some alignemt in the 4 bolts but not much. How did you reference center?

 

[norvalwilhelm]

They are always offset to the right. The motor is also offset. You can do basically nothing to the alignment, well easily that is.
More important is vertially linement.
If the transmission points down say 1 degree the rearend pinion must point UP 1 degree. The angles must be the same but opposite. This is easy to adjust with the shim in the pinion nose.
I have adjusted my rearend both up and slightly to the left but the left right thing is not easy.
Years ago I run a string down the centerline of the motor, transmission the rearend cover and made the pinion fall into this alignment but it involved slotting 3 of the 4 mounting holes in the crossmember, aligning the pinion when welding heavy washers over the slotted holes and reassebling and checking.
This is the short version of how it is done but it involves alot of work.
If you want more details I could go into it
Once corrected my shifter never, never vibrates regardless of speed.

 

[black_81_vette]

If I were you idgo to a reputable shop and have them look at it.Peace of mind is priceless!!!

 

[68Roadster]

It may just be the body, mine is off as well if you use the body as a reference. If your 69 is like my 68, pull the door sil plates and look thru the holes in the fiberglass down to the holes in the top of the frame (one side has the hole up front, the other towards the back). They should line up. If they don't, that may be your problem.

 

[norvalwilhelm]

If I were you idgo to a reputable shop and have them look at it.Peace of mind is priceless!!!

Your normal mechanics will not know about alignment of the parts. A specialty race shop building car would but the average or better then average mechanic doesn't get into this type of alignment.
Most do not build engines/transmissions or rear ends.
Your average alignment specialist doesn't know about bump steer and how to eliminate it.
Your average mechanic will not know about vet brakes and their special requirement.
There are 3 licensed mechanics in my family and they only know about these things because I have drilled it into them. They know the basics but not the fine points.

 

[black_81_vette]

A reputable shop IE corvette repair shop should be more than qualified to tell you if its askew or not.Yes Ive known and worked with so called ase certified mechanics too,but there is always bad techs giving the good ones a bad name.

 

[norvalwilhelm]

It's not that the mechanics are bad it's just that they don't get into it. One close alignement specialist and liscensed mechanic wouldn't know about bump if I didn't constantly talk about it.
Can you actually tell me what is wrong if I gave you toe changes as the car was moved through a range of motion? Could you tell if the car's outer tie rod was too high or too low? The tie rod the right length due to the slope of the line?
Unless you are trained in this exact field your mechanic just wouldn't know.

Race shops string the drive train for alignment. I have a poor picture of my car with strings on it aligning the drive train somewhere.

 

[JHL]

Don`t know about the rear end but the engine is definately not in the middle of the chassis. It is offset by about 2" to clear the steering on the drivers side so I wouldn`t be surprised if the rear end was not dead center.

Have a look at the head on pic on my site and you will see the scoop is offset to the passenger side.

J.

 

[norvalwilhelm]

This is a poor shot of my vet after stringing. If you look close you will see strings hanging down with nuts attached to them to act as plum lines. A string is run down the centerline of the crank and the centerline of the rearend and anything that doesn't line up is moved until it does. It is involved, time consumming and sometimes takes alot to put it right.
Sorry for the poor shot and the tire is leaning out because both the upper and lower strut rod are disconnected and the lower strut is holding the tire up. I run a 6 link suspension.