What are the common problems when you drive down the road at a speed of say 55-60 mph and let of the gas pedel a little bit and you start to feel a shake, add gas and it seems to go a way mostly?

This is on a 4Dr JK with a 3" lift Teraflex long arm kit, has 4.88 gearing and is an auto tran with 35" tires.

Dave

 

I would start with checking tire pressures and getting them rebalanced.

 

It has a new set of tires and wheels on it. Would this be caused by drive lines or gearing in the axels?
Dave

 

Just because they are new, doesnt mean they are balanced properly. Simple question, but are the lugs properly torqued and the rims fully seated? I had my 33's balanced 2 times by the original installer then again by a truck shop with a road force (i think that is what they called it) balancer before they did it right. So a total of 4 balances on a brand new set of tires.

Speed specific wobbles that you can drive through are almost always a tire balance issue.

Have you double checked all your fasteners/longarm brackets/trackbar etc. for proper torque?

Where do you feel this shake? is it in the steering wheel, or elsewhere?

I would start by checking the easy stuff first to try to resolve the problem. Drivelines and gearing questions i will have to respectfully decline to answer as they are out of my realm of knowledge.

 

^^^ have to agree with happy...

Check tire balance could be your issue. Did you recently go mudding? Check your rims for caked on clay or mud inside the rim and clean them out.

Also, IF you got new rims check to see if there is a retaining clip(s) on the lugs (basically a very thin washer type clip). If you still have the clips on these lugs, remove them as this could cause your vibration issue as the rim may not fit snug.

Also, you may have a bummed up tire that the tread is seperating. Try the easy stuff before you sweat about gears, tranny, or out of balance driveshaft or worn out U-joints.

 

have u reset the pcm recently with a tuner, or disco the battery??i get a similar feeling after i change my tune with the superchips... i think its the pcm relearning all the engine's paremeters.. its almost like a sputter, but no loss of power, and as u said when u apply gas it goes away...idk if this is your issue, but its what popped into my head....

 

I should have giving more information up front about this problem.
I purchased the JK stock in 2007 and all was well. I did one of the first few 3" skyjacker short arm lift kits that was out in 2007. Drove it and it had some viberations then, the shop could never help out in getting fixed. Finnaly they told me to re-gear it and so I did. That just changed the viberation point to a higher speed setting. Since I was told that the Skyjacker kit I had was "prototype kit" and I got screwed from how I purchased it from. So I had Teraflex install the Long arm kit to repair the problem. That didn't really fix any it, its better but not right.

So now I was told that two of my rims were bent so I purchased a new set of tire and rims and still I have the problem. I really believe that it has something to do with the gearing that the first shop did.

It feels like it is in the rear end or center.

Dave

 

Just a few ideas....

Drive your JK in 4x4 on the pavement (straight stretch) with not much traffic and then try it back to 2wd...if there is no change in the vibration between 4x4 and 2wd then you can basically rule it's coming from the rear end area. But if it get's worse in 4x4 than 2wd then it's more likely up front the issue.

Have a look at your U-joints on your driveshaft could have a seized up or bad U-joint on the axle also, take a look to see if you lost any driveshaft weights...could have a out-of balance Driveshaft??

Was there alot of difference in tread wear from the tires (used vs new?) Typically I purchase all 4 new tires to ensure the tread depth is similar. Also, maybe those older tires are toast (out of round, blown belt)>

 

"Finnaly they told me to re-gear it and so I did. That just changed the viberation point to a higher speed setting."

It does sound plausable that it may be an out of balance driveshaft. however i am leaning towards a caster problem based on what you said. My reasons being: I get a vibration about 65mph. I KNOW it is caster related as I have been fiddling with it off and on for a while. Adjusting my caster does not make the vibration go away, but what it does do is change the speed at which i feel it. I never drive over 70 so I want to get it inched up to not give me issues until around 80. I have been getting it moved up, but not quite where i want to be yet.

I had my driveshafts checked for balance and they passed just fine. Are you on the stockers or aftermarkets? You can check to see if it is a driveshaft by alternately removing them and going for a test drive. It would also help you narrow down more if it is coming from the front or rear of the Jeep.

I wish I knew more about drivelines and gearing to help you out there but I am way out of my element in all things gearing. Have you popped your diff covers and inspected your gears for any obvious signs of misallignment or damage? Or had anyone check them/bearings for wear?

What gets me is you only feel this when letting off the gas? that means the driveline isnt under load, it is essentially idling down so any looseness/play would be more noticable then. You had this same issue with two different lifts, so when swapping them, besides the gearing, what DIDNT change when you swapped lifts? driveshafts/trackbars etc? I would inspect those items first as they are common to the problem.

Sorry I cannot be of more help. this is a stumper for me.

 

keep us posted in what was causing your issue!