Slight driveline vibrations after 4.25 inch combo lift

finchmeister08

finchmeister08

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Jun 25, 2019
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Eufaula, AL
I'm interested in measuring my driveline angles from the t-case and the rear axle, but I'm a bit confused. I've seen this picture in a few threads when searching through Google. I'm curious why I would only measure the rear axle/drive shaft angles, but not the output shaft of the t-case/driveshaft angles?

101180
 
Slow down here a moment.

You said you installed a 4.25" combo lift, right? If so, did you install a SYE and CV driveshaft at the same time, as well as adjustable control arms (at least in the rear)?

If not, then you can't adjust your driveshaft / pinion angle at all, and you shouldn't be either.

Assuming you do have a SYE, CV driveshaft, and adjustable control arms, the angle of the driveshaft at the transfer case output is absolutely irrelevant as you have a CV / double cardan driveshaft. The angle that matter is the one posted in the photo above.

Why would the angle at the transfer case output matter with a double cardan driveshaft? That's what the CV joints are there for.
 
Tell us more about your rig, is your rear driveshaft still stock? Did you install a motor mount lift or a tcase drop kit after installing the 3" suspension part of your 4.25" kit?
 
Chris said:
Slow down here a moment.

You said you installed a 4.25" combo lift, right? If so, did you install a SYE and CV driveshaft at the same time, as well as adjustable control arms (at least in the rear)?

If not, then you can't adjust your driveshaft / pinion angle at all, and you shouldn't be either.

Assuming you do have a SYE, CV driveshaft, and adjustable control arms, the angle of the driveshaft at the transfer case output is absolutely irrelevant as you have a CV / double cardan driveshaft. The angle that matter is the one posted in the photo above.

Why would the angle at the transfer case output matter with a double cardan driveshaft? That's what the CV joints are there for.
Click to expand...

yup, installed it over the weekend. did the MML and everything. but no SYE. Your explanation clarifies that for me now. I've read that I can add washers between the t-case skid plate and the frame to help eliminate the vibrations. I did that yesterday, and I can't really tell if it did anything. I just got new tires w/ spacers (33x12r15 BFG A/T) put on as well along with an alignment so it could be any number of things i guess.
 
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finchmeister08 said:
yup, installed it over the weekend. did the MML and everything. but no SYE. Your explanation clarifies that for me now. I've read that I can add washers between the t-case skid plate and the frame to help eliminate the vibrations. I did that yesterday, and I can't really tell if it did anything. I just got new tires w/ spacers (33x12r15 BFG A/T) put on as well along with an alignment so it could be any number of things i guess.
Click to expand...

Got it. The MML was a good idea to go along with the body lift for sure.

Since you have the stock driveshaft and no SYE, the only way to get rid of the vibrations will be to use washers (and longer bolts) between the skid plate and where it attaches to the frame. No one can tell you how many washers you'll need, so you'll have to play around with them and stack them until the vibration is gone.

Since you mention also adding new tires, there's a very good chance the vibrations you're feeling are from improperly balanced tires. This happens way more often than most people think, as most shops don't have enough experience balancing the larger tires we run. So, I would rule out the tires before anything else, as that is again, a very common issue that many people will mistake for driveline vibrations.

Also, be sure to have it aligned! That's very crucial.
 
Ok so your MML helped but you need to keep that stock driveshaft configured as is. Your rear axle's pinion angle must be the same as/parallel to the tcase output shaft angle. That you're still getting vibrations after the MML installation is troubling since that's normally more than enough to eliminate the vibrations caused by a 3" suspension lift.

If you add washers between the frame and tcase I'd go no more than 1/2" of drop and see what happens.

Make sure you get your alignment right away. That 3" suspension lift increased your front axle's toe-in angle substantially and if it's not restored back to its proper angle it will cause your tires to quickly wear unevenly. Would you like to set your toe-in angle on your own? It's easily done and with a modicum of care your results will be just as accurate as an alignment shop can produce. No exaggeration. All you need is a tape measure, big pliers, and a wrench.

Your rear pinion angle and tcase output shaft angles must be like this... parallel to each other. Don't worry about what the driveshaft angle is, it is inconsequential for the factory driveshaft when you only have a 3" lift.

2joint_angle.jpg
 
from some other research, the automatic transmission is slightly long than the manual. well, i have the automatic and the very well could be causing my issue as well i guess.
 
Check my angles this afternoon.

Between 10/11 down at the output shaft yoke

Between 18/19 down at the drive shaft

Between 13/14 at the axle yoke

Not really sure what this means. It took me 5 1/2” washers to get there, and barely enough threads to torque the bolts down with factor bolts. 1/2-13 bolts from Tractor Supply didn’t work for me. Which is weird cause I took a factory bolt with me to test on a 1/2-13 nut and it worked.
 
Here's the thing I've learned from my own experience with driveline angles.

The numbers don't actually matter that much. What matters is that it doesn't vibrate anymore. Now I'm not saying to ignore the numbers completely, I'm just saying that you may find they don't end up being exactly what you expect them to be.

Also consider that driveline angle can vary based on a number of things such as the amount of weight in the car when you drive it. For instance, if you adjust driveline angles, then put 4 people in the car and a bunch of gear, you can imagine that the angles will change.

Just food for thought. I've never been the type to mess with transfer case drops. The correct way to do it is a SYE, CV driveshaft, and adjustable control arms. I realize of course some people don't have the money for that, but it is makes things much easier.
 
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Looks like you have between 7 and 9 degrees at the tcase and 4 or 6 at the axle, if your numbers are what they seem to be. If you have 7 at the t case and 6 at the axle, probably close enough. If you have 9 at the case and 4 at the axle, not close enough.

The angles cancel each other out. They need to be close to be vibration free. The picture Jerry posted shows this pretty clearly.

Also, does it vibrate under acceleration? That usually points to the u joint angles not correct.

Old u joints get stiff in the area they have not been running after alot of miles. If they were running at 3 degrees for 80000 miles, they are not going to like 6 or 9 degrees now. May need to change them.

Paul
 
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Is does vibrate between 20 and 30 mph. One thing I’ve noticed though is that it does it in the morning while it’s cool outside. I feel it right under my seat.

In the after noon where it’s 80+ outside, it doesn’t do it, or it does but it’s so faint that I don’t notice it.
 
How many miles on your rig? I tend to agree with Paul's suspicion of u-joints. New rear ujoints and a new Adams front driveshaft made a world of difference in mine.
 
Are we talking about the Zone Offroad combo kit? If so, I installed one of those a couple of months ago. I had vibrations around 30 or 40. Rather than install washers (which I know works, but just feels like a half-solution to me, but that's just me), I put adjustable rear control arms in and dialed in the pinion angle exactly as Jerry describes. Drives like a dream now, no SYE required.

The fact that your vibes only occur when it's cold is strange though. I'm no expert, but that seems more like a tire issue - like pressures and balance is off, but when they heat up and the pressure goes up a few PSI it works itself out somehow.
 
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BlackJeep said:
Are we talking about the Zone Offroad combo kit? If so, I installed one of those a couple of months ago. I had vibrations around 30 or 40. Rather than install washers (which I know works, but just feels like a half-solution to me, but that's just me), I put adjustable rear control arms in and dialed in the pinion angle exactly as Jerry describes. Drives like a dream now, no SYE required.

The fact that your vibes only occur when it's cold is strange though. I'm no expert, but that seems more like a tire issue - like pressures and balance is off, but when they heat up and the pressure goes up a few PSI it works itself out somehow.
Click to expand...

So you're saying that you just added upper adjustable arms and adjusted the pinion angle without the installation of an sye?

Not trying to hijack this but interested in vibe relief also....
 
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