Stock rear suspension question

[Greg63]

Okay, here is the scenario;
I just replaced all my front suspension - everything from the front crossmember to the tie-rods-I mean everything. I had the front end fully aligned professionally from a recommended shop and it rides and tracks great. It is all stock and now new.

The guy who did my front end alignment noted that there is a difference in the rear suspension; + 1/2 a degree on the drivers side and - 1/2 a degree on the passenger side.

What does that mean? Today I measured from front tire to rear tire on each side and found that there is a difference of 3/4" from one side to the other on my wheelbase.

Now I know that there is no adjustments in the rear suspension, and I bolted the front crossmember into the only holes that were in the frame and there were not any oval holes for adjustment.

Any idea how to true up the wheelbase to get it close (add distance on the drivers side and subtract distance on the passengers)?

Greg

[ChiefRocka]

What condition are the trailer arm bushings in ??

No evidence of past frame damage ??

[Greg63]

John, I replaced the bushings with new GM ones 15-18 years ago and probably have not put 4000 miles on the truck in that time.
The frame shows no sign of any damage - I can vouch for that since 1981.

Greg

[ChiefRocka]

Hmmmm.....mabey there was just an imperfection in the manufacter/assembly of the chassis/suspension parts at the factory.

Mabey one trailing arm is slightly longer/shorter than the other ?? Wonder is the TA crossmember was riveted in square ??

How is the rearend mounting to the trailing arms ?? Were the arms removed to install the bushings ?? There is not much play in the u-bolts, saddles and holesin the TA's. , but you might try and loosen the ubolts on both side, and try and shift the rear end equal amounts to make up that 3/4"....Like I said, I dont think you'll have much play there, though.

Worse come to worse, I guess you could shorten on of the TA's....

With a 3/4" difference...is there a visible 'dogtail' when driving ?? Probably not, I would guess.

Later

[Greg63]

I looked at the crossmember and the trailing arms. The crossmember is in there good with factory rivets.

I noticed the trailing arms are both "wavy" on their top sides (the metal deflects an 1/8" up and down in a couple of places along their length). I had never noticed that before and I don't believe it has anything to do with their length - they are both like that.

When I replaced the bushings I did it with the rear end in the truck. It was tough getting them in but they went in.

The rear end was swapped out 10-12 years ago. I looked at the availability of moving one side ahead and the other back - I don't believe I could even get a 1/8" out of that.
It would be nice if I could move each side of the rear end on the TA's 3/8" to make up the 3/4" total.

I have never noticed the truck doing anything other than riding normal. Now I know that there is a difference I am searching for a corrective measure (no pun intended).

If worse comes to worse I will just leave it alone, but I would prefer to make it "perfect".

Greg.

[ChiefRocka]

Originally Posted by Greg63

I looked at the crossmember and the trailing arms. The crossmember is in there good with factory rivets.

I noticed the trailing arms are both "wavy" on their top sides (the metal deflects an 1/8" up and down in a couple of places along their length). I had never noticed that before and I don't believe it has anything to do with their length - they are both like that.

When I replaced the bushings I did it with the rear end in the truck. It was tough getting them in but they went in.

The rear end was swapped out 10-12 years ago. I looked at the availability of moving one side ahead and the other back - I don't believe I could even get a 1/8" out of that.
It would be nice if I could move each side of the rear end on the TA's 3/8" to make up the 3/4" total.

I have never noticed the truck doing anything other than riding normal. Now I know that there is a difference I am searching for a corrective measure (no pun intended).

If worse comes to worse I will just leave it alone, but I would prefer to make it "perfect".

Greg.

Didn't think there was any movement.....the wavy steel has nothing to do with it.

Well, the easiest would be to leave it alone...otherwise some repositioning of soem sort is in order. Let me know what you come up with.

BTW, I see you still haven't 'sold' your grill !!

[poorboy]

Just out of curiosity were the wheels perfectly straight when the measure ment was taken? If not then that might be the difference in the #'s.

[Greg63]

Originally Posted by poorboy

Just out of curiosity were the wheels perfectly straight when the measure ment was taken? If not then that might be the difference in the #'s.

Good observation - yes they were. I had just driven straight out of the garage.
Greg.

[Greg63]

Well, I have found the source of my problem, and I am not sure I want to deal with the solution.

I just went under the truck with my carpenters square and placed it inside the frame against the crossmember. I did this on both rails and found what I expected - the crossmember is not square in between the rails. It is slightly ahead of square on the drivers side rail and slightly behind square on the passengers side rail. Squaring this up would probably bring my wheelbase in line on each side.

As I see it the solution is to grind off all the rivets holding the crossmember, shift it into square, then bolt it back together.

The part I don't like about that solution is the possiblity of future movement in the crossmember by the rivet holes being elongated so I can bolt it back square, and I don't have a welder.

What would any of you do?

Greg.

[blackedoutharley]

Meet me at the border and I will make the problem go away... (bring the title!).

J/K

I would find somebody with a welder and just tack the member after you bolt it in.

[1restorick]

Greg, I would visit a reputable frame shop and have them check all frame dimensions against the factory measurements and tolerances. Then, if it's determined to be a significant problem, ask if it can be straightened. It sounds like the frame could be slightly diamond shaped. However if this were the case, other signs would be noticeable like the front bumper would likely not be parallel. I would not try to remove all of the rivets from the crossmember, until I researched all possible remedies. Bottom line, these trucks are very old and were not built perfect from the factory and many have lived hard lives. If it looks ok and drives ok, you need to decide how perfect you would like it to be. I have 63 C10 myself and I have never checked these dimensions. After hearing your story, I'm not sure that I want to know the answer. Best of luck, your truck is beautiful.

Rick

[Greg63]

Right now I am of the mind to leave it alone. Before I knew about this I had no reason to believe there was a problem.

Now the problem is this: I know myself well enough that sometime down the road I will want to correct this problem (perfectionist) and most likely will regret getting into it (realist).

Thanks for everyone's input.

Greg.

[justcuz]

Lots of times you can find frame measurements online. You measure diagonally across the frame in a couple of places where crossmembers are square in the frame. If the offset is consistant at 2 or more points your frame is diamond shaped and can be plulled back into shape. I used to go to a guy that did semi truck frame repair. A pickup was easy money for him, and he did great work.