Pinion Angle Adjustment Questions

[Karl]

So I have my SYE in and DC rear shaft. I had my diff regeared to 4.56 and I'm fairly satisfied with the results.

I still have some vibrations (0-15 kmph) and they lessen with speed but I'm pretty sure they are still there. And I've come to the conclusion it's my pinion angle. I think it's worse at lower speeds because when under torque it will point the diff up a little more making it more in line with the drive shaft and lessening the angle hence vibrations? I feel like when I had an alignment they should have adjusted my pinion angle too....
Anyway, questions.

1. In order to adjust the pinion angle, I need to only lengthen the upper control arms correct? I think the lower controls could affect it as well but they are primarily for determining position of the axle and ideally that should be further back so I'd rather not shorten them to angle the diff up. so UPPER control arms?

2. Are my lines correct in this picture? I saw that the angle finder should go where the two white arrows point to so I just put lines down on those surfaces and this is the result. I think the angle is a little harsher than illustrated simply because I couldn't get a picture of it nicely.

3. Can I pop out the uppers and adjust on the ground or do I need to jack it up?

Thanks, I really need to get rid of this vibration.

 

[Chris]

Once the axle is set where it needs to be using the lower control arms, you tighten them up and don't mess with them again, period.

From then on, your adjustments are done by adjusting the upper control arms only. After you've got your pinion angle, release the tension on one of the control arms so that it isn't binding whatsoever. Then you can tighten them up.

I am assuming of course that you have double adjustable uppers, which will make your life much, much easier.

Yes, your lines are correct. The angle finder can go in both of those locations.

You want the pinion to be about 1-2 degrees lower than the driveshaft, as it will rise a bit upon acceleration.

I'll also add that once you get good enough at this, you don't even need an angle finder at all. You can just look at it and eyeball it.

Some TJs are more sensitive than others too when it comes to the pinion angles.

 

[starkey480]

1. You can adjust pinion angle with just adjusting the uppers. Make sure to cycle your axle to be sure nothing is contacting as the more you rotate back things can start to hit like diff on gas tank and track bar on gas tank etc. if this happens you need to shorten lowers and adjust again.
2. Place angle finder on one of the two flat spots to each side of the diff cover. You will get a number between 70 and 80 most likely. Subtract that number from 90. Ex: you get 75*. 90-75 = 15 so your pinion angle is 15. Make your pinion angle 1* lower than the angle of your driveshaft.
3. Place jack right under the pinion. Barely jack up and the bolts holding the uppers should be nice and loose so you can pull them out by hand. Jack up or lower the pinion as needed. Place uppers back in place and make sure the bolts spin freely by hand on both sides before taking the jack away. Don’t worry if they are same length.

 

[eastbloc]

I always placed a socket on top of the ujoint inside the yoke and angle finder on top of it... looks like there is an easier way

Starkey480 #3 method is what i do.
If jack is out of option, i have done it with a combination of wheel chocks and highlift. Exhausting experience, but doable.

 

[starkey480]

I always placed a socket on top of the ujoint inside the yoke and angle finder on top of it... looks like there is an easier way

Starkey480 #3 method is what i do.
If jack is out of option, i have done it with a combination of wheel chocks and highlift. Exhausting experience, but doable.

Nice socket works as well. Here is the spots I measure pinion angle. They are exactly 90 degrees to the pinion angle so again subtract the number you get from 90

 

[Karl]

1. You can adjust pinion angle with just adjusting the uppers. Make sure to cycle your axle to be sure nothing is contacting as the more you rotate back things can start to hit like diff on gas tank and track bar on gas tank etc. if this happens you need to shorten lowers and adjust again.
2. Place angle finder on one of the two flat spots to each side of the diff cover. You will get a number between 70 and 80 most likely. Subtract that number from 90. Ex: you get 75*. 90-75 = 15 so your pinion angle is 15. Make your pinion angle 1* lower than the angle of your driveshaft.
3. Place jack right under the pinion. Barely jack up and the bolts holding the uppers should be nice and loose so you can pull them out by hand. Jack up or lower the pinion as needed. Place uppers back in place and make sure the bolts spin freely by hand on both sides before taking the jack away. Don’t worry if they are same length.

Ok It looks like I had it all correct. As for where the angle finder goes, the spot on the diff I pointed to with the white arrow should be just as good as those two locations you circled on the back. Frankly I could do both and check. If they are the same then doesn't matter.

My biggest concern is how hard it will be to take the damn arms off and adjust. I like the idea of the jack under the pinion. I'm really hoping the jack under the pinion works well. Unfortunately I don't think my upper control arms are double adjustable.

 

[starkey480]

Ok It looks like I had it all correct. As for where the angle finder goes, the spot on the diff I pointed to with the white arrow should be just as good as those two locations you circled on the back. Frankly I could do both and check. If they are the same then doesn't matter.

My biggest concern is how hard it will be to take the damn arms off and adjust. I like the idea of the jack under the pinion. I'm really hoping the jack under the pinion works well. Unfortunately I don't think my upper control arms are double adjustable.

It’s really not that bad of a job once you get into it. I also have single adjustable. Post where your angles are at now. The angles look about right just eyeballing it