Andor

Hey everyone. I'm getting a vibration/noise that starts almost dead on 40 MPH+ There's nothing I can pick up before that. It occurs coasting or accelerating with no difference between the two. I know its difficult to diagnose sounds but its kind of like the sound of rumble strips. There is a also vibration I can feel in the floor.

I just got my tires balanced and rotated to rule that out but it didn't help.

I recently replaced shocks, sway bar links, and axle u j joints which fixed the other issues I was having.

My wheel bearings didn't have any play when I checked them by pushing and pulling at 12 and 6. But I'm not ruling that out

One added thing is the there is a long pretty steep hill on my way home when I'm accelerating pretty hard up it to go 30-40 MPH it doesn't seem to happen but when it level out and goes down it starts again.

Thanks in advance

Andor

Anybody ?

SteveMongr

This is tough to diagnose. What is your jeep? Is it stock? Have you checked the driveshaft u-joints?
From the description this is difficult to speculate on further. Feeling it through the floor has me concerned.

Andor

99 Cherokee stock. Just daily driving. When checking the drive shaft u joints does the vehicle need to be off the ground? I crawled under initially and all the joints along the driveshaft felt tight. Is there anything particular to check? I'm new to working on cars, everything I've learned has come searching jeep forms in the past few months. My fear is something differential related because that would likely send my buddy to the junk yard. Is there anyway to rule that out? It's more sound than vibration especially in the 40 mph range.

centuryhouse

Did you lift it, or replace your rear springs with HD springs?

I ask because I replaced my rear springs with HD which boosted the height a few inches, and at that time I started getting a little vibration at around 40 mph.

SteveMongr

If it is related to the differential, the entire axle assembly can be replaced for about $200. First would be to check the fluid level. Then remove differential cover and inspect internals (be ready with a catch pan for the 2 quarts of nasty fluid that will drain out). Could likely use fresh gear oil anyway.

To check u-joints, driveline needs to be relaxed. In other words, on level ground, chock wheels, place tranny in neutral, then crawl under and using both hands turn driveshaft back and forth, there will be some movement in the axle and transfer case but the u-joints should have zero movement.

Wheel bearings can also cause a grinding noise at speed and when really bad , can sound like rumble strips.

Andor

Thanks Steve. I appreciate it. I already turned the corner on staying with the jeep and was starting to kick myself although I didn't have any other option except another older vehicle. It's good to know it'd be possible to avoid differential work if it came to that which is way out outside of my abilities and budget. I'm going to Check the drive shaft as you suggested. Would bad wheel bearing (s) cause vibrations or would that not be typical? Does the fact that it doesn't happen while going up a hill have any significance to you? Sorry for writing a book but you seem like a knowledgeable guy and it's good to get other views on thing

SteveMongr

A wheel bearing should not really cause vibrations, just noise/grinding, and will build up heat.
Yes, not happening while powering uphill is a clue but I cannot put my finger on a definite reason. There is a weight shift, and subtle changes in driveline angles.
Perhaps you could find a fellow jeeper in your area to assist in person. There are a lot of local groups on facebook.
While inspecting u-joints, also inspect leaf springs. Springs should have a small amount of arch, if they are flattened or curving upwards that they can be a contributing factor.

Also, pictures would help in this situation, we may be able to spot an issue.

Andor

Finally got a break in the rain and checked the driveshaft today. Nothing felt blatantly loose. There is a small amount of rotation in the front drive shaft which seems normal. Behind the transfer case (towards the back) if I push up and down on the closest U joint to the transfer case there is a small amount of play when its in neutral. The play seemed to be in the piece that goes into the transfer case not the U joint its self. Is this normal? When out of neutral that small amount of play isn't there. The leaf springs are pretty flat.


I've read of removing the front drive shaft. Would this help rule anything out?