Shadowwar

Ok got a weird one and need some help.

2000 jeep cherokee sport 6 cyl 4wd. stock with jasper motor put in 6000 miles ago. The whole jeep has 112000 on it now. IT is running great until now.

There is a bad vibration at 1500 rpm only while moving and part throttle.

Front end is good. Axle joints are fine.

Basically if i coast at say 20mph and slowly and easy get back into throttle to bring to 1500 rpm there is such a vibration that it will rattle your teeth. If i give it more throttle or let off the pedal it goes away. It only does it while moving and under power braking it does not do it at all. Engine is running fine and passed a cylinder misfire and balance test. This seems driveline but all u joints and driveshafts seem fine with no play.

It also does not matter wether 4wd or 2wd.

Any help is appreciated!

Shadowwar

Just bumping for one last shot in case someone has run into this.

Thanks!

LeRoy90laredo

i had a similiar issue.
my u joints looks fine but once i replaced them it was solved.

Shadowwar

Thanks Leroy!

Gonna yank the driveshafts this weekend and check.

Cherockee

X2 on u-joints. Also possible that you have a bent or unbalanced driveshaft (or wheel or any number of other things connected to the engine and tires.

Shadowwar

Thanks will post back with results!

LeRoy90laredo

Thought the same about possible an unbalanced driveshaft but thought that it be more reoccurring throughout the higher rpms.

Chickenfloss

Is it 1500rpm at 20mph only or at any speed and 1500rpm?

Shadowwar

Well i can get it to do it up to about 30-35.. then the coasting rpms are more than 1500 so it doesnt do it anymore.

1500 rpm very light throttle is the constant here.

And again only does it when rolling.

Shadowwar

Ok still at a loss on this one. The vibration got slightly worse and will do it in park now at about 1300-1500.

Can feel vibration on throttle lever at throttlebody and holding a screwdriver against the exhaust. Also can see steering wheel bouncing around.

Did check the ujoints by pulling front driveshaft and it all seems fine. all cups rotate and no play.

Pulled inspection cover to check torque converter to flexplate bolts. All nice and tight.
Checked front balancer. Ring is intact and no wobble. It almost feels like a bad balancer but this one seems fine.
Double checked motor mounts and they are fine.

There are about 10000 miles since i put the jasper motor in it. She is also comlaining that oil pressure gauge seems to read higher now than usual. Getting 80 psi when cold and 45 psi when warm at idle with 5w30 oil.

Any one have any other ideas. I am running out of things to check.

LeRoy90laredo

Did you check the rear driveshaft as well? It wasn't mentioned.

Shadowwar

I checked the driveshafts and they are fine. all cups rotate and no play or binding. Its gotten slightly worse now and does it not moving but not as bad under load going down road. So driveline is back out again.. I am leaning towards the tps and going to test that tomorrow or monday. Thanks for the input.

Shadowwar

Ok replaced the tps and its better but still there. any other ideas?