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

I would think that you could for a small lift, But most people do not buy adjustable arms for small lifts. Hence the lowered skid option. Also you would need to keep and eye on the slip shaft to spline engagement. I have seen pics where people ran out slip and the shaft separated.
 
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MarkAlan

Agree, just wanted to see a real explanation besides just seeing it on the internet.

Nothing worse that I saw it on a forum or somethgin like that.

When I was at NASA I watched a young but real smart simulation guy give a day long presentation on the program he was on and comparing it to a previous program (the X-38 program). He got the bulk of his information about the X-38 from the internet (Wikipedia to be exact). Well Wikipedia was wrong, way wrong and those of us that were on the X-38 knew the errors and those errors caused his simulations to be very incorrect and I was quite embarrassing, not to mentions the weeks wasted with bad information.

Or with that oil filter video showing how bad FRAM is, but no technical reason why.

That is why I was asking from guys with the experience about rotating the axel (which is what that young simulations person learned the hard way)
 
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John I just tuned in so I may be out of school on the conversation...

I had the exact same issue and it was control arm bushings.

you can actually Park a Jeep and have someone step on the brake when you rock it back and forth and see the control arms move unnecessarily

If that is the situation you will be absolutely thrilled at the improvement new bushings will bring.

We all wish you the best man.
 
...just wanted to see a real explanation besides just seeing it on the internet.

If you want to roll the pinion upwards at the rear axle and change the slope of the driveshaft, fine...there's no problem with doing that, but you still have to get the universals working in harmony. Thus, you run a double-cardan shaft with an intermediate link that equalizes the angles and velocities between the two joints on either side of said link. The universal that's at the pinion yoke should be aligned with the driveshaft itself, lest you end up with a momentum problem on that end.
 
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Sundowner

Now we are getting some reasons as opposed to just do it. These reason could help someone decide between droping the Tcase and/or rotating the Axle depending on the lift and what they want out of the lift.

Thank You
 
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Sundowner

Now we are getting some reasons as opposed to just do it. These reason could help someone decide between droping the Tcase and/or rotating the Axel depending on the lift and what they want out of the lift.

Thank You

You're welcome, but you weren't getting "just do it" before; the information was present...it simply wasn't clicking.

For most of us, there's no decision to be made regarding a case drop: it's an ugly and graceless solution to a problem more correctly solved elsewhere, and which introduces more obstacles than it removes.

Oh, one other small thing:

Axle = part of a Jeep.
Axel = part of a figure skating routine.

;)
 
Not really a just do it, but more of a do not rotate the axle, must be parallel. I understand the drive line, but I have not worked on many TJ's so I thought that there must be a good reason that I have seen the following:
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.

Adjusting the pinion angle should not be done with just a 2" lift.

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.

drop the tcase as recommended.

It was clicking, and that is why I was asking why not to rotate the axle (was there something specific to the TJ's), but it turns out that it is ok to rotate the axle, even with the stock drive shaft as long as one stays within all the specifications required which is what should be stated.
 
John it is funny that you say that about simulations. I work in the EMI world, and all we hear is how great simulations work, and how they replace testing etc. And to some degree that is correct, but trying to make people see and understand that the simulation is only as good as the data that has been entered into the model makes me want to beat my head on the wall. Yes they have a purpose and can save time and money if and only if they are correct. We use them a lot for lightning strikes at the pad. But trying to use them on a new box is very difficult due to not knowing or having a grasp of how a unit will react to things makes it nothing more than a guess. Considering we have a full lab downstairs, and can walk a unit down to conduct a full test, it is much faster and you will know exactly what the outcome will be when the test is finished. No guess work involved. But we can sit around guessing and changing models without getting up from our desk and finding out the real answer.
 
Cool, I was with CPAS, and one of the parameters we had to verify/inprove ws the accuracy of the simulators of the revocery chutes for Orion. BUT like you stated, we tested and tested and tested to verify the simulations (and qualify parachutes and other stuff). One must have real data to simulate with or else garbage in = garbage out. Spent 5 years traveling to Yuma doing that.
Are you at the Cape?
 
I think is is best looked at from a cost perspective. As usual you have many ways of fixing a problem. But you also have a budget. Most of the time people will run out and buy a lift slap it on and think they are good to go. Then they have issues, and are out of funds to mitigate the issues. They easiest way, and least expensive way is to drop the case. Two bucks for washers and you could have the problem solved. If not a MML about 150 or less and that could be a solution to the problem. Once again if both are needed you still come out about the cost of 1 adjustable arm. Well for a good adjustable arm.
 
No I would not live in that area again. I am at MSFC Huntsville. I lived in Melbourne for a few years. Loved to surf, hated the area.
 
It was clicking, and that is why I was asking why not to rotate the axle (was there something specific to the TJ's), but it turns out that it is ok to rotate the axle, even with the stock drive shaft as long as one stays within all the specifications required which is what should be stated.

It's okay to rotate the axle to align the pinion and the stock driveshaft as long as the stock driveshaft is a double-cardan shaft that's already aligned in such a way, and as long as you aren't using those goofball cam bolts. If those conditions aren't met, then no, it's not okay, and you'll spend a night in the box.
 
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I thought there were issues with the cam bolts not staying tight. Maybe thats what MrBlaine was talking about the holes would wallow out.
 
Axle = part of a Jeep.
Axel = part of a figure skating routine.

Yeah, but don't foget:

83565
 
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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.
Hi Jerry,
Dealing with same issue in this thread. We took off rear drive shaft and drove it. All shuddering/ drive line vibrations are now gone. Based on that, does this seem like pinion angle issues? If so, do you think shimming the t case with washers would improve my issue? (Note: 4” lift with standard t case drop). Thanks!
 
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.
Hi Jerry,
Dealing with same issue in this thread. We took off rear drive shaft and drove it. All shuddering/vibrations are gone. Based on that, does this seem like pinion angle issues? If so, do you think shimming the t case with washers would improve my issue? (Note: 4” lift with standard t case drop) Thanks!
 
Unless you're driving an Unlimited, a tcase drop is not enough to eliminate the vibrations a 4" suspension lift will cause. 4" is where a standard SWB TJ needs to have a SYE and CV driveshaft installed.
 
Unless you're driving an Unlimited, a tcase drop is not enough to eliminate the vibrations a 4" suspension lift will cause. 4" is where a standard SWB TJ needs to have a SYE and CV driveshaft installed.
Thanks Jerry. It’s a 98 TJ. Before going the SYE and CV driveshaft route, would the washer shims on t case likely improve the issue? If it is the pinion angle? Again, the fact that all issues went away with rear shaft disconnected leads me to think it’s the angle.