Can't recall what rear axle torque thrust is. How is it adjusted?
What is torque thrust?
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Photon440
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With the gas pedal? 
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Axel wrap?
Possibly. I saw a question on A bodies
about it and he was talking about shims and leaf springs. Maybe what he was referring to was drive shaft and pinion angle
about it and he was talking about shims and leaf springs. Maybe what he was referring to was drive shaft and pinion angle
Kernel Sanders
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Although not the best diagram below... the thrust angle is the alignment of the rear axle.
It can be corrected by using shims between the front mounting point of the leaf spring mount to the frame of the car.
It can be corrected by using shims between the front mounting point of the leaf spring mount to the frame of the car.
If the angle is a positive number, the axle is biased towards the right like in KS's pic above and will need shims on the drivers side. If a negative number, the axle is pointing to the left and needs shims on the right side.
beanhead
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If it's too far out of whack, you might end up going down the road like this!!
(Fast forward to 3:50...)
(Fast forward to 3:50...)
Hilarious. How do you go about checking and correcting?
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Sharp-looking wheel. I used to have a set of my 69 but it doesn't help me solve my problem LOL
Where is the measurement taken and how exactly do you correct it?
I learned about it this last summer when the shop that does my alignments got a new 4 wheel alignment rack. Their old one had things that attached to all 4 wheels, but it didn't measure the thrust angle. The car I had done was +.25 degrees, so the rear end wants to push the car to the right. So I have to loosen the front leaf spring hanger on the drivers side and add shims between the hanger and the frame to bring that side back. Problem is that you really can't get it perfect without being back on a rack. I am going to get it close and then have the car realigned next spring. Pulled a string tight from the rear axle flange all the way up to the front frame rails and measured the best I could. From these measurements, I was off about 1/2". I made up a .15" shim and just last night stuck it in. I actually think it is pretty close. I bought a Hotchkis 3003 shim kit and will take that with next spring to get it perfect. Then I plan on making a solid plate the correct thickness.
Nate S
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For the home alignment person there are a couple ways. Figure that this is not something that was planned on being adjustable on a B-body. If the car was never hit it’s overwhelmingly likely it’s fine. Also figure that up to .25 degree, who cares? You can’t see a car crab-walk down the road with less than that. Then last, if it’s over .25 you probably need a frame straightening machine more than a shim.
So, first thing is get the car flat with the front wheels straight. Eyeball rear to front across the outer edges of the tire and see what you’re looking at, probably the outer edges of the front tire, notice where. Do the same on the other side. If it looks exactly the same go have a beer and worry about something else. .25 degree is almost exactly .5” up front. It’s on both sides of course so if you see the very outer edge of the tire on one side and 2” out in space on the other you’re off by an inch (of 1/2 degree) and need to see how screwed you are.
Same setup. Pull out your tape measure, hang it on the rear rim and measure up to the rim on the front wheels. Same from side to side? With this measurement .25” of difference = .25 degree of thrust. Good, now measure to some piece of frame just in case you don’t really have the front wheels straight. Should be the same. If these quick checks have you off by <.25 degree leave it alone. If it’s .25 or more, start looking for where it got smacked. Half of your unibody is >.25” shorter than the other side. Ouch.
Oh, you can shim back one side to trim. 1” per degree. It won’t make any difference at all.
So, first thing is get the car flat with the front wheels straight. Eyeball rear to front across the outer edges of the tire and see what you’re looking at, probably the outer edges of the front tire, notice where. Do the same on the other side. If it looks exactly the same go have a beer and worry about something else. .25 degree is almost exactly .5” up front. It’s on both sides of course so if you see the very outer edge of the tire on one side and 2” out in space on the other you’re off by an inch (of 1/2 degree) and need to see how screwed you are.
Same setup. Pull out your tape measure, hang it on the rear rim and measure up to the rim on the front wheels. Same from side to side? With this measurement .25” of difference = .25 degree of thrust. Good, now measure to some piece of frame just in case you don’t really have the front wheels straight. Should be the same. If these quick checks have you off by <.25 degree leave it alone. If it’s .25 or more, start looking for where it got smacked. Half of your unibody is >.25” shorter than the other side. Ouch.
Oh, you can shim back one side to trim. 1” per degree. It won’t make any difference at all.
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