Expert Advice Needed for Drive Line Angle Shims (1 Viewer)

[78fj40mg]

Hey all,

My rear drive line angle has been bad ever since I installed the new OME Medium Duty suspension, 2.5 inch lift, and I've been getting some vibration coming from the rear end. I had some time today so I checked the angles with all four wheels firmly on level ground, the results were based on the TREMEC Drive Line Angle finder iPhone app:

These TREMEC readings were not correct maybe it was my fault.
See my accurate readings bellow using an angle finder


Angle 1. at the parking brake was 08.01 Down

Angle 2. at the drive shaft was 12.2 Down

Angle 3. at the 3rd member flange and the drive line angle was calculated to be 04.2 Down

Am I correct to assume that it needs to be raised 4.2 degrees?

Should I use a 3, 4 or 5 degree shim?

I don't want to over or under compensate the angle deficiency.

Thanks in advance for your valuable input!

 

[B y r o n]

Maybe the information found in this thread will help.

 

[78fj40mg]

Thanks for the link Byron.

 

[78fj40mg]

Bump

Does anyone have any shim selection information?

Thanks in advance for your valuable input!

 

[reddingcruiser]

After re-reading your post the first thing I noticed is the p- brake angle at 8.01. GENERALLY, engine angles (which the t-case out put angle is related to) should be around 3 degrees. This could be related to the ground you are parked on, but be sure. Your motor mounts could be shot.

Assuming you have a OEM FJ40 drive shaft setup, the angle of the t-case output and the pinion should be parallel. If you have an magnetic protractor (or angle finder), the angles should be equal, above and below "0".

Call Georg at Valley Hybrids. I bought steel caster shims from him before.

IMHO, the best way to fix this permanently is to buy new spring perches, cut the old ones off, set the angle, weld it up and be done with it.

 

[78fj40mg]

After re-reading your post the first thing I noticed is the p- brake angle at 8.01. GENERALLY, engine angles (which the t-case out put angle is related to) should be around 3 degrees. This could be related to the ground you are parked on, but be sure. Your motor mounts could be shot.

Assuming you have a OEM FJ40 drive shaft setup, the angle of the t-case output and the pinion should be parallel. If you have an magnetic protractor (or angle finder), the angles should be equal, above and below "0".

Dick,

Thanks for braving to answer my questions!

When I measured the drive line angles the vehicle was sitting firmly on a level concrete floor in my shop.

I agree that the motor mounts need to be checked and will do that tomorrow, however, where did the 3-degree engine angle come from? Is this in the FSM?

Yes, the drive shaft is an OEM FJ40. The t-case output and pinion flange are not parallel.

I just rechecked all the pertinent angles and the results were as such:

· Engine Valve cover – 2.5 degrees DOWN

· Oil pan – 1.9 degrees DOWN

· P-Brake – 2.5 degrees DOWN

· Drive shaft – 9.7 degrees DOWN

· Third member – 6.3 degrees UP

I ran the above angles several times and was yielding different results each time which tells me the iPhone app sucks and it lacks accuracy, therefore I will be purchasing a real analog angle finder to verify all the angles prior to making any drive line alignment changes.

Thanks again!

 

[Pin_Head]

The stock angle for the transfer case flange and differential flange is 90 degrees from the flat ground. In other words, the pinion axis is horizontal.
You need to measure on a flat surface and if it is not flat, then you need to subtract the inclination of the ground.

If you post measurements, add a drawing so we can understand what you mean. Up or down is relative to direction.

 

[reddingcruiser]

Three degrees of rear downward angle is pretty typical of most gasoline engine factory installations, but not by any means standard. My point way I was anything considerably in excess of that would be suspect.

Like @Pin_Head said, if you're not on level ground you need to take into account existing slope. You also need to consider your suspension. I try to make sure the flat center of the frame is level and parallel to the ground and built my SOA setup accordingly.

Only two angles are important, 1) the pinion angle, and 2) the t-case output shaft. Every other angle you measured on the engine relates to the output angle (you can't change any without affecting the others )
Have you dropped the drive shaft so you can measure accurately across the flanges?

 

[78fj40mg]

The stock angle for the transfer case flange and differential flange is 90 degrees from the flat ground. In other words, the pinion axis is horizontal.
You need to measure on a flat surface and if it is not flat, then you need to subtract the inclination of the ground.

If you post measurements, add a drawing so we can understand what you mean. Up or down is relative to direction.

I put together this diagram depicting all pertinent information.

 

[78fj40mg]

Three degrees of rear downward angle is pretty typical of most gasoline engine factory installations, but not by any means standard. My point way I was anything considerably in excess of that would be suspect.

Like @Pin_Head said, if you're not on level ground you need to take into account existing slope. You also need to consider your suspension. I try to make sure the flat center of the frame is level and parallel to the ground and built my SOA setup accordingly.

Only two angles are important, 1) the pinion angle, and 2) the t-case output shaft. Every other angle you measured on the engine relates to the output angle (you can't change any without affecting the others )
Have you dropped the drive shaft so you can measure accurately across the flanges?

As I mentioned above the truck is on a perfectly level concrete slab so no worries there. I'll drop the drive shaft in the morning and I'll report my findings.

 

[78fj40mg]

@Pin_Head I removed the drive shaft and also picked up a magnetic angle finder.
Please let me know if a 3 degree shim will be enough.
Thanks in advance!
Mike

Here are the results.

Pinion flange angle reading

Close up of the above pic

E-brake angle reading

 

[Pin_Head]

Yes, approximately 2-3 degrees difference. The rear pinion needs to rotate down, so the fat end of the shim goes to the rear. Probably not enough to cause problems even without shims, so why do you want to shim it?

 

[78fj40mg]

Yes, approximately 2-3 degrees difference. The rear pinion needs to rotate down, so the fat end of the shim goes to the rear. Probably not enough to cause problems even without shims, so why do you want to shim it?

I'm experiencing an audible drive line vibration as such I don't want to prematurely wear the U joints.

 

[Efjay]

Hi Mike, check this site, lots of good info.

BillaVista.com-Driveshaft Bible Tech Article by BillaVista

I went through this a couple of years back with my 2.5" lift, although I have a 5 speed box so my driveshaft is shorter than yours.
Yes, it is true that on single cardan driveshafts your output flange and pinion flange need to be parallel, however if the operating angles of the u-joints at each end are excessive you will still get vibrations (as I did). Remember, if you shim your pinion down, you will also be increasing the u-joint angles at each end.
Having a longer driveshaft you may be OK, but the the only way I could sort mine out was to have a double cardan driveshaft made up and shimmed the pinion up to point at the output flange.

Also, make sure your driveshaft yolks are 'in phase', as this alone will cause vibrations.

Very frustrating I know. Hope you can sort it.

 

[Chungas Revenge]

Thanks for posting this up Mike. One of the systemic problems with "lifts". It seems simple enough but there is still a great deal of confusion regarding over/under or no correction, especially among the unwashed masses (I.E ME!!)...

I'll be taking this on in the near future. 2.5" lift and a 1/2" on the shackles put me at on or about 3(+) degrees as well. No hi-jack intended. I figure we are rowing the same boat!!!

 

[78fj40mg]

Received the rear pinion angle correction shims which I'll be installing later today. The shims are manufactured by Belltech, dims 2 1/2" wide, 3 degree correction angle. The kit also included two three inch long bolts which hopefully I will not need.

 

[cjgoode]

I can't imagine if you have a properly installed 2.5 spring lift that it would throw anything out of angle enough to need shims for the rear axle. Something else is likely the problem, most likely the phase of the drive shaft like someone else pointed out. When you were installing the lift, did the drive shaft ever get separated and slid back together? Usually people only need shims on the front axle to fix the caster, and that makes these angles even worse not better.

 

[78fj40mg]

Thanks Chris! The shaft U joints are in phase, the problem as I see it is the pinion is approximately 3 degrees off, as such I'm experiencing some vibration coming from the rear. I checked the motor/trans mounts and in fact the rear ones show signs of cracking and deflation which will replace in the spring time and hopefully realign the output flange and the pinion flange. In the interim I decided to use shims to correct the misaligned flanges and to also see if the vibration will subside. Another related issue is the rear diff is tilted so much that I cannot fully fill it with oil and the only way I know to fix this is by shimming the pinion down in order to level out the oil fill plug.

This is the only pic that shows the diff oil plug but the angle of the pic doesn't show the diff angle I'll take another pic shortly.

 

[cjgoode]

You can only check the angle when it is sitting on the ground and level or the weight is 100% by the axles. With it on a lift being supported by the frame will not work.

 

[78fj40mg]

You can only check the angle when it is sitting on the ground and level or the weight is 100% by the axles. With it on a lift being supported by the frame will not work.

When I measured the drive line angles the vehicle was sitting firmly on a level concrete floor in my shop.

Here are couple of pics of the diff angle.

diff angle

ebrake drum angle