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Help! Rear can't get aligned 1975

cor66vette

Member
Joined
Nov 23, 2013
Messages
19
Location
FL
Corvette
'66 convertible,
There is a current thread about DIY aligning a C3, and one post mentioned the rear alignment. Instead of adding to that thread, I thought to seek some advice here, in a new thread, regarding the issue I'm having with the rear in my '75.

When I went for an alignment I was able to get the front done without a prob, but the rear was another thing. The alignment guy, although not at a "Corvette" shop, was trying real hard but couldn't get it right. I have a tentative appointment to get it done at a Corvette shop, but in the meantime, how much of a problem is it when the rear is "off"? Does it affect other parts of the rear ... 1/2 shaft u-joints, etc.? I figure it depends on how "out" it is, but generally speaking, does it affect more than just tires? Thanks.
 
The toe-in of the rear wheels is just as critical, if not more so, than the toe-in of the front wheels. It goes beyond just tire wear and contributes heavily to safe handling of the car particularly when the car is being pushed hard.

Camber is also adjustable, but is not as critical.

Why can't your guy get it right?
 
Loose wheel bearings or bad trailing arm bushings would prevent him from getting a good alignment on the rear just like it would on the front. Maybe he just couldn't get the bolts loose at the front of the trailing arms and gave up. Does it look like the bolts have been loosened or even had a wrench on them? How about the camber adjusters?

Tom
 
Loose wheel bearings or bad trailing arm bushings would prevent him from getting a good alignment on the rear just like it would on the front. Maybe he just couldn't get the bolts loose at the front of the trailing arms and gave up. Does it look like the bolts have been loosened or even had a wrench on them? How about the camber adjusters?

Tom
I agree with Tom..others..yes essential to get it right. BUT FIRST get everything else set up and correct..check wheel bearings, bushings, ride height set and even side to side, same for front. A good align really can't be done with failing bushings etc off. Then..my advice is do not use factory manual specs. I did a lot of checking..you can too..so don't just believe me..but go to a few web sites for alignment for the vette..(Duntov has good info) to get new specs, front and rear. Both need shim kits to be on hand so you may want to get them if your shop does not have them. Then it is a 4 wheel align best checked on the latest laser computer systems. When done, to modern spec, handling is night and day better..no more wandering. By the way, tires that may already be worn badly due to miles of poor alignment, will never handle well.
Nick
 
The IRS on these cars gets abused and worn, all affecting alignment. Assuming your shop knows to start with the rear and go to the front, what was the issue exactly? As mentioned there is Toe and Camber on the rear.

Before you bring the car anyplace else take a close look yourself. Areas to check would be the rubber bushings in the strut rods, and spring bolt ends, the steel spring for being flat or curling upward, excessive axle end play in the diff, bent or rotted trailing arms, play in the spindle bearings, missing toe shims or cotter pin for them. If you can post pictures of your IRS we might be able to spot things. If the IRS is original and rusted then you may be facing some work before you can align the car. I do not do alignments but when I bring in my cars I will bring them to a shop I know and trust, bring in ss toe shims and new cotter pins and the spec I want the car set to. They don't mind doing my cars or those I did because it's all new and fit, it makes it much easier to remove and replace shims that are not corroded together and a mess.

If you had a 63-70 they're worse since they used 2 hole steel shims that require unloading the spring, removing the bolt, replacing the bolt, loading the spring and checking it- after rolling the car to settle the suspension again. Many have converted to the slotted SS shims and drilled the frame for the cotter pin.
 
I have a guy that I absolutely trust. I put on new tires last summer and had him do the alignment even though the old tires were worn perfectly. The right guy and the right equipment will make a big difference in the way your car drives.

Tom
 

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I have a guy that I absolutely trust. I put on new tires last summer and had him do the alignment even though the old tires were worn perfectly. The right guy and the right equipment will make a big difference in the way your car drives.

Tom
Agree..in my car, since I had done front bushings, wheel bearings, shocks, and had done rear trail arms, camber struts, shocks, bearings..all the parts were new, nuts and bolts fresh and free of rust, so nothing frozen. I ordered the shims and cotter pins etc so had them on hand, then wrote out the very specific instructions and order of alignment and specs..and at a shop that knows me and my cars, with good history of work (and my $$), met with the shop foreman and the alignment tech to go over it and get agreement on what and how to do it. Still, after the job, the computer print out was not close enough to spec.,.and shop foreman agreed they would do align again and get it closer. They did..
I used same shop to disconn computer, install new mech advance, vac advance, tuned distributor, plugs, wires, reset timing and adjust carb. More $ but job well done..and a shop that knows I am "fussy" as to being on spec. tho I have to be polite..they have lotsa biz...and are about the only shop in town for muscle cars, older performance cars, older vettes etc..I need them prob more than they need me. But they are willing to listen. to use my specs not factory for alignment and tuning/timing etc the .I changed mechanics mind about ported and manifold vac. using (manifold on non emission engines).
Nick
 
I align mine using 1/16" nylon contractor's string, a tape measure, an aluminum extension ladder (or a long piece of pipe), a piece of 1/8" X 3" X 15" steel, and an angle finder. I'll give you detailed instructions at the same time I give you the instructions for aligning your own front end; around Saturday or Sunday if you don't mind waiting a few more days.

It's very easy to do once you learn how and it takes no brains whatsoever. The hardest part is adding or removing the trailing arm shims but if you soak them ahead of time with WD-40 it'll be much easier.
 
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... Maybe he just couldn't get the bolts loose at the front of the trailing arms and gave up. Does it look like the bolts have been loosened or even had a wrench on them? ...

Tom

Wow, a lot of good advice here, thanks a lot guys.

I may have described the situation without good detail. Yes, you are correct, Tom. I believe the alignment guy had a problem getting the bolts loosened.

I'm in the process of replacing the tie rod ends and idler arm (unrelated PM) and I'll need the car aligned, so I'll have the rear addressed at that time. I'll soak the bolts overnight before I go.

Should I bring new shims with me?

Thanks again for the input.
 
I align mine using 1/16" nylon contractor's string, a tape measure, an aluminum extension ladder, a piece of 1/8" X 3" X 15" steel, and an angle finder. I'll give you detailed instructions at the same time I give you the instructions for aligning your own front end; around Saturday or Sunday if you don't mind waiting a few more days.

It's very easy to do once you learn how and it takes no brains whatsoever. The hardest part is adding or removing the trailing arm shims but if you soak them ahead of time with WD-40 it'll be much easier.


If you are lucky enough to have the slotted shims, as on my 81, they lift right out..drop right in.
A water witching wand, a piece of old dry chicken bone, and a indian head penny help too.
N
 
I'm in the process of replacing the tie rod ends and idler arm (unrelated PM) and I'll need the car aligned, so I'll have the rear addressed at that time. I'll soak the bolts overnight before I go.

Should I bring new shims with me?

Thanks again for the input.

I'd be prepared for far worse. Frequently the whole area is corroded into one big lump.
 
. I'll soak the bolts overnight before I go.

Should I bring new shims with me?

Thanks again for the input.[/QUOTE]

Yes..spray whatever you van with PB Blaster or equiv..Liquid Wrench etc..You might even see if you can get a wrench on and move a bit..Yes..have a shim kit, maybe new bolts, cotter pins. Same for front..shims at min. Now..research specs on what you will specify for alignment for your year car..so you can tell shop. and you should have rear ride height set where you want it via the rear spring bolts, if those bushings are bad, time to replace em first. Measure each side of the car at rear side, floor to various points..frame, to trans half axle, to wheel well edge to get car even. you will have em do 4 wheel align..not just rear..tho you do rear first..then front..at same time setting steering wheel to dead straight. Having the car ready for the final touch which is the align is the key to being pleased with the accuracy and ride.
Nick
 

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