FJ40 Alignment Questions - Axle centering and Camber shims (1 Viewer)

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Thanks to those of you that have helped on other threads! I thought I'd try starting another focused on today's task at hand: alignment.

The truck is a 1974 FJ40 freshly reassembled. I initially had the front camber shims on backwards, that made it handle evil. It still handles terribly but that was an improvement. Here is what I find and have questions;

1. I used a laser and line setup I use on the race cars, using the centerline of the truck chassis as the reference point.

2. Both axles are seated towards the driver's (left) side. The front is 3mm too far left and the rear is 5mm too far left. Looking at how the spring perches and Ubolts sit, it doenst look like there is a lot of room for adjustment. Seems like this is something to loosen up the ubolts and try to pull the axle over a few mm each?

3. The front crossover rod runs out of adjustment (the rod is too long?) to get the steering centered. The front left tire is 10mm toe in, and the front right is 0 toe. so total toe is probably pretty close to right. Lengthening the drag link just made the steering wheel re-center crooked. Do I need to shorten my front center-pivot-to-passenger-side-knuckle rod a bit shorter to gain more steering centering adjustment?

4. Perhaps if I can get 3mm of shift to the front axle that will naturally pull the center-pivot-to-passenger-side-knuckle rod back into adjustment range?

5. I had some spare camber shims and when putting the rear axle on I guessed (maybe totally wrong) that these thin ones with the thick end forward would straighten the driveshaft angle. Now its all together and settled in, it looks like the driveshaft angle out of the rear diff aims above the transfer case. Like if the shims were out, it would be better? Whats the practice on shims in back? THe springs are re-arched ~3" lift...

THanks for the advice and help. Everyone loves pics...

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Take a look at my first couple of posts on spring pins in this thread. In looking at your spring pins in the pictures that show them it looks like they don't fit the hole in the axle mounting plate. If the pins are not centered in the mounting holes that could explain by your axles are offset. I'd also remove the caster plates and start from there. Rear drive shaft mounting plates should be the same angle or as close as possible, transfer case and third member.
 

pb4ugo

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You can loosen the ubolts and try to center the axles. I'm not sure it's going to make much of a difference. It's not a race car. Leaf spring suspensions have a lot of movement in them. Let's call the rod going from wheel to wheel a tie rod. Having more toe in on side means the steering is not physically centered. Whats your caster angle? Your rear pinion is too high and will eventually hurt the pinion bearings or u joints. You want the pinion angle and the driveline angle to be parallel to each other, or as close as you can get them.
Checkout tom woods website and look for something like driveline angles 101.
 
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DangerNoodle

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Are your angles equal on the pinion flange and the t-case flange? These angles need to make parallel lines, otherwise, you are going to be in for some nasty vibrations at speed. The angles look kinda funny to me for a non double-cardan joint.

pinion_angle_bad_angles.png


As for alignment, I wouldn't even bother. The pins should hold it pretty dang close. 5mm isn't much. It would be a whole array of things, from unsquare frame, unsquare perches, slightly misaligned holes, not quite exact measurement etc. Have you had it on a rack to see exactly how far out everything is? Much more and I would be worried, but not over that. Don't overthink this.
 
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Thanks guys for the images and suggestions. I respectfully say, I am not overthinking this if the truck is undriveable, which it is.
 

DangerNoodle

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Thanks guys for the images and suggestions. I respectfully say, I am not overthinking this if the truck is undriveable, which it is.


I think the backward front shims and shims in the rear is doing it for you. I'd pull the rears and flip the fronts and see how it does.
 

John Smith

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First remove the shims from the rear axle. You don't want your pinion pointing towards your xfer case flange, as you are not running a double cardan shaft out back. Second, if your steering still sucks and is wandering with the 4 degree shims with the fat side towards the front of the truck, you need more caster and thicker shims. Or shorter shackles.
 
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2. Both axles are seated towards the driver's (left) side. The front is 3mm too far left and the rear is 5mm too far left. Looking at how the spring perches and Ubolts sit, it doenst look like there is a lot of room for adjustment. Seems like this is something to loosen up the ubolts and try to pull the axle over a few mm each?

Likely just play in the shackles bushings which will swing right or left a bit with every turn. And should unless you're running some kind of super hard poly spring eye/shackle bushings and have everything reefed down with spinach. Doing that will ruin any ride quality you may hope to have on a freshly resto'd rig while she's still on pavement. Off road will be horrible - even dangerous in the rocks when your suspension starts lifting tires before you even get to a tough obstacle..

Check to make certain your spring center bolts are in the holes in the perches on each axle housing. Then rock/shove the whole body/frame to the left and the body should center over the axles as much as Mr. Toyoda's build team crafted into your specific 40. These things weren't made with modern laser precision standards.

3. The front crossover rod runs out of adjustment (the rod is too long?) to get the steering centered. The front left tire is 10mm toe in, and the front right is 0 toe. so total toe is probably pretty close to right. Lengthening the drag link just made the steering wheel re-center crooked. Do I need to shorten my front center-pivot-to-passenger-side-knuckle rod a bit shorter to gain more steering centering adjustment?

If I follow you here then it's your steering wheel that isn't centered if both front wheels are set equal in toe-in degrees... yes? You only need a degree or two of "toe-in" on each side. I don't remember spec but I barely run a degree iirc. Since the "front crossover rod" is not wheel specific (there's no center connection point) then, once you've turned both wheels to the same degrees of toe-in on each side, you can adjust either the "center-pivot-to-passenger-side-knuckle rod" or the drag link length (or both) to re-center your steering wheel and steering box. You want all three:

1) Steering wheel centered

2) Steering box centered

3) Equal toe in at each front wheel

Adjust the toe-in first. Then go back and attend to the steering box followed by the steering wheel.

4. Perhaps if I can get 3mm of shift to the front axle that will naturally pull the center-pivot-to-passenger-side-knuckle rod back into adjustment range?

Probably not. Again: 3-4-5mm is inconsequential on these vehicles. Any one of 8 spring attachment points on your frame may have been welded imperfectly by today's standards. Just go with it. I know full well how tough that is after all the work to get your 40 looking sharp, but trust me here.

5. I had some spare camber shims and when putting the rear axle on I guessed (maybe totally wrong) that these thin ones with the thick end forward would straighten the driveshaft angle. Now its all together and settled in, it looks like the driveshaft angle out of the rear diff aims above the transfer case. Like if the shims were out, it would be better? Whats the practice on shims in back? THe springs are re-arched ~3" lift...

Reverse the shims to rotate the nose of your rear pinion downward. You have them set for a spring-over axle. HTH.

EDIT: I should have said "...rotate the pinion shaft of the rear differential downward until it is parallel to the transfer case output shaft or slightly downward."

The pinion will rotate upward slightly under load.
 
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