I have the dreaded "Jeep shakes on take off" syndrome

egclassic

egclassic

TJ Enthusiast
Joined
Nov 16, 2016
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Location
Cincinnati, OH, United States
So now that I've gotten all my maintenance work done and front fender replaced and painted on my "new to me" 2000 TJ, I figured its time to deal with the shaking on take off issue I seem to have.
This jeep has a cheap RC 2" lift and BF Goodrich Mud Terrains that were on it when I bought it.
The issue is that it shakes when I take off from a stop. It only last for a second or two until I get moving. It seems to be worse if I'm taking off on an uphill incline rather than on a flat grade.
I've read it could be a number of things, like various mounts or pinion angles. So where do I start to diagnose the issue? I know it sounds like I answered my own question, but I just need some insight on how to go about checking these.
Thanks
 
Drivetrain shaking while accelerating is normally caused by the rear pinion angle being too high. Has anyone used cam bolts or adjustable length control arms to raise the rear pinion angle? It should not have been with the factory rear driveshaft still installed.
 
Jerry Bransford said:
Drivetrain shaking while accelerating is normally caused by the rear pinion angle being too high. Has anyone used cam bolts or adjustable length control arms to raise the rear pinion angle? It should not have been with the factory rear driveshaft still installed.
Click to expand...
How would I go about adjusting the pinion angle if I have stock control arms? Or do I need to just lower the T/C by shimming the skid plate?
 
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egclassic said:
How would I go about adjusting the pinion angle if I have stock control arms? Or do I need to just lower the T/C by shimming the skid plate?
Click to expand...

Jerry is right, I had the same issue. I put a mask on the issue by lowering my TC skid like you said but adjustable control arms are the real fix so you don't sacrifice clearance.


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egclassic said:
How would I go about adjusting the pinion angle if I have stock control arms? Or do I need to just lower the T/C by shimming the skid plate?
Click to expand...
Adjusting the pinion angle should not be done with just a 2" lift. Since your control arms are stock so the pinion angle hasn't been raised, odds are good you just need to drop the t-case skidplate by about 5/8" by stacking enough washers around all six t-case skidplate mounting bolts, placed between the frame and skidplate. Due to the indentation the washers sit in, you will need more like 3/4" to 7/8" worth of washers to lower the skidplate 5/8? Just use heavy duty galvanized washers with a 1/2" bolt hole through them. Support the skidplate with a jack, loosen all 6 bolts but only remove all the bolts on one side at a time to insert the washers. That will keep the skidplate in alignment instead of slipping off to the side if all six bolts were removed at once. Dropping the skidplate 5/8" will reduce the excessive angle the rear driveshaft u-bolts are operating in that causes the vibrations.
 
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dylansalrin said:
... adjustable control arms are the real fix so you don't sacrifice clearance.
Click to expand...
Actually no, since with the stock rear driveshaft you have to keep the pinion angle as the factory set it. The rear pinion angle must remain parallel with the tcase output shaft with the factory driveshaft.

There are two fixes for drivetrain vibes... drop the tcase skidplate or install a SYE kit with an aftermarket CV driveshaft. It's only with an aftermarket CV driveshaft when the rear pinion angle should be adjusted with adjustable length control arms. :)
 
Jerry Bransford said:
Adjusting the pinion angle should not be done with just a 2" lift. Since your control arms are stock so the pinion angle hasn't been raised, odds are good you just need to drop the t-case skidplate by about 5/8" by stacking enough washers around all six t-case skidplate mounting bolts, placed between the frame and skidplate. Due to the indentation the washers sit in, you will need more like 3/4" to 7/8" worth of washers to lower the skidplate 5/8? Just use heavy duty galvanized washers with a 1/2" bolt hole through them. Support the skidplate with a jack, loosen all 6 bolts but only remove all the bolts on one side at a time to insert the washers. That will keep the skidplate in alignment instead of slipping off to the side if all six bolts were removed at once. Dropping the skidplate 5/8" will reduce the excessive angle the rear driveshaft u-bolts are operating in that causes the vibrations.
Click to expand...
Yeah, I am kind of dreading lowering the skid plate as I have read all the issues about the nutserts spinning, but if thats what I need to do I will.
 
The large SAE bolts holding earlier TJ skidplates like yours are long enough to drop the tcase as recommended. The smaller metric bolts they started using around 2003 are not.

If you ever need new tcase skidplate bolts, Grade 5 is fine. No need for Grade 8. :)
 
As Jerry stated: "rear pinion angle" - had the same issue w mine, after installing a 3" lift. Bought a SYE and an Adams shaft and after installing them, the vibs / shakes are all gone.


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Sorry to hear that @Scotiarebel and It has good reviews at extreme terrain. So I bought it and installed mine 2 months ago, I thought I fixed my death wobble already but since I installed my RC death wobble came back and I'm not happy about it.


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sjaydomingo said:
Sorry to hear that @Scotiarebel and It has good reviews at extreme terrain. So I bought it and installed mine 2 months ago, I thought I fixed my death wobble already but since I installed my RC death wobble came back and I'm not happy about it.
Click to expand...
DW is often caused by nothing more than having installed larger tires that were imperfectly balanced. And the larger the tire, the more important that they be perfectly balanced to prevent DW. And I don't care if they were recently balanced, not many tire shops are willing to get tires balanced any better than to what they consider "good enough" which for the type of front-end the TJ and many trucks have, is not good enough. The bigger the tire, the more critical perfect tire balance to preventing DW. Yes I made that point twice for added emphasis. :)
 
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Jerry Bransford said:
DW is often caused by nothing more than having installed larger tires that were imperfectly balanced. And the larger the tire, the more important that they be perfectly balanced to prevent DW. And I don't care if they were recently balanced, not many tire shops are willing to get tires balanced any better than to what they consider "good enough" which for the type of front-end the TJ and many trucks have, is not good enough. The bigger the tire, the more critical perfect tire balance to preventing DW. Yes I made that point twice for added emphasis. :)
Click to expand...

What should I do to fix it, yes I have 33's on my TJ.


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sjaydomingo said:
What should I do to fix it, yes I have 33's on my TJ.
Click to expand...
Other than insuring the tires are perfectly balanced as I suggested above? :confused:

Be aware that some tire shops have to be pushed to spend enough time to insure the tires are perfectly balanced. It took three trips to my tire shop in one day before they finally believed me that they needed to spend enough time to get them perfect. The third time was the charm.

Also insure your toe-in is properly adjusted. An improper toe-in adjustment can encourage DW.
 
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