Need a Good Jeep Mechanic

[Gezza57]

Hi John

I have a 2007 KJ CRD.

I have a Murchison 3" lift installed and this was done a couple of years ago.
I have spent quite a bit of money on the car including "tunit" chip, arb which bar to name a couple of mods.

My problem is that on fast acceleration I get a vibration through the car.
If I thump it, I get an almighty shudder through the car and it seems to lose
power. I have sought advice from the ausjeepoffroad forums and it was
suggested it mat be the torque converter. However I have sent the car to an auto trans expert and the say there is nothing wrong with the TC.
I have had the car in jeep kraft in Perth for the past two weeks and they have pulled everything down including the transfer case, removed drive
shafts, checked the diff etc. after what I expect to be a massive bill,
they are throwing their hands in the air with no resolution to the problem.

At the time of writing this it is still at Jeep Kraft. I am particularly concerned during their testing they displayed some confusion as to the difference between full time and part time 4WD stating they thought part time was usable on the bitumen. Now they are trying to tell me there is no difference in performance or feel whether it is in full or part time 4WD. That is the drive train should bind up on bitumen in part time. My concern now is I am worried they have screwed up the cv joints or the like.

Have you heard of this problem and can you give me some guidance please.
By the way I am in Perth.

I look forward to your response with thanks


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[Methamon]

Found this on another site possible issue with yours maybe:
Drivetrain vibrations that only occur during acceleration are usually caused by the rear driveshaft u-joints vibrating from either an excessively high pinion angle (when modifications have been made to allow that) or a bad u-joint in the driveshaft. Both of those would be my immediate first suspects. But that you have a 4" suspension lift makes me think that your u-joint angles are simply excessive. Fixing those excessive angles is best done with a SYE kit and aftermarket CV driveshaft. Dropping the t-case via spacers can also reduce the excess angles but I doubt you could drop it enough within reason to cure the vibrations from such a tall suspension lift. With a 4" lift, installing a SYE (slip yoke eliminator) kit into the transfer case and aftermarket CV driveshaft is the right solution

Just trying to help

[Gezza57]

Thanks Charliebrown

I have asked Jeep Kraft to lower the transfer case when they reinstall it.
Being a 3" lift, half to one inch should offset the lift effects for this lift (I hope)

Thanks again

[senatorjohn]

Hi Geeza
Just got back onto this post. Sorry for the delay.
Your lift may play havoc with the driveshaft angles and cause the vibration. some set ups are touchy, others are not. The driveshaft angles to the gearbox output shaft an the final drive pinion should be the same, otherwise the velocity variations created at each joint do not cancel each other out. The angle the joint works at also has a maximum value for smooth operation. The apparent loss of power I have no clue on.
If someone cannot diagnose the problem without dismantling multiple components, good chance they will never find the problem. I do not dismantle until I know the cause or at least the particular component or area causing the problem.
Sorry I cannot be of any help.
John

[Gezza57]

Thanks John / Charliebrown

Guys you hit the nail on the head. I had the tfer case lowered 1" and that has solved the problem.
Sacrificed a bit of height but it was worth it. The car runs like a new machine.

Thanks for your help.