Drivetrain Knock/Vibration HELP!!!!

[xjhighroller]

Ok guys,

I have a 1995 Jeep Cherokee XJ that is driving me nuts. It has a nasty knock that primarily occurs when the truck is in gear and under a load that progresses with speed and turns in to a heavy vibration. when the truck rolls forward you can hear it ever so faintly, but it really stands out when you put your foot on the gas and even more so when you ride the brake a little. I am almost positive that its somewhere from the motor back because I nosed the front end up to the curb in the rain and power braked it and yes, the knock was there. It’s first started as a light knocking sound that over 2-3 weeks progressed into what is now pretty nasty sounding.

The list of things that I have done:

1. Replaced the Pinion and Carrier Bearings in the rear end by local shop
2. Replaced the wheel bearings in the rear end by local shop.
3. Had my rear Chromo shafts checked to make sure they weren’t bent.
4. Had the local Shop Check the rear end to make sure that nothing was broken in the ARB air locker.
5. Had the rear driveline rebuilt by reputable local shop.
6. Replaced the transfer case with another rebuilt transfer case.
7. Replaced the trans mount bushing. Old one was shot.
8. Took truck to Transmission shop and they said no way its the automatic transmission.

What is the problem? I have a slip yoke eliminator, the transfer case is the same as the one I replaced, the driveline is a Tom Woods w/CV that has now been rebuilt, the angles all look fine. I have the guy at my drive line shop crunching the numbers for me as far as the angles go, but said he thinks its fine, I have heavy duty transfer case drops that I made out of steel round stock, and still have the problem.

Any Brainstorming would be greatly appreciated.

Thanks,

Scott

 

[MTBracer367]

loose torque converter bolts?:dunno:

kinda sounds like what happened to my friends 89 and his was that the torque converter bolts came loose i've heard of people ruining their fly wheels form that happening

 

[xjhighroller]

That is the one thing that I have not checked. I did check the Flexplate for cracks and made sure that the bolts were tight, but not the Torque Converter. Is dropping the Transmission any harder than dropping that transfer case?

 

[xjhighroller]

i started thinking after taking off the inspection cover and looking at the flex plate and bolts. does the torque converter not turn unless the tires turn or does it spin the whole time while the motor is running even at idle?

thanks

 

[jeepinwi]

Is there any play in your front driveshaft? My wife's 00 XJ had a nasty vibration from a worn out front driveshaft. Replaced it with a new shaft and vibration went away completely.


The torque converter is bolted to the flex plate, which is bolted to the crankshaft. It will always be spinning when the engine is running.

 

[xjhighroller]

I rebuilt and balanced the front driveline and I dont even have it in right now.

 

[xjhighroller]

its a nasty Knock as soon as the wheels start to turn mainly under load

 

[jeepinwi]

Lets try to isolate the problem. Does the knock speed change with engine RPM's if revving in neutral? Does the knock sound change with each transmission shift? Is the sound still present if vehicle is run in 4lo? Does the knock happen with ech tire revolution?

May be worth a shot to pull off the rear diff cover to make sure all the bolts there are tight.

Maybe remove your rear driveshaft and run the trans through the gears to see if the sound is still there. If so, that would eliminate the rear axle.

 

[xjhighroller]

Lets try to isolate the problem. Does the knock speed change with engine RPM's if revving in neutral?
it does not knock when in when you rev the motor in nuetral.

Does the knock sound change with each transmission shift?
it stays consistant through all gears, but progress with speed mixed with gas. if you coast the sound is not pronounced but is still present.

Is the sound still present if vehicle is run in 4lo?
I dont know about 4Lo but if i drive with just the front drive shaft in 4hi the sound is much lighter but still there.

Does the knock happen with ech tire revolution?

it seems to be that way. only if the wheels turn.


May be worth a shot to pull off the rear diff cover to make sure all the bolts there are tight.

this was all just rechecked.

Maybe remove your rear driveshaft and run the trans through the gears to see if the sound is still there.
I jacked up the rear end on jack stands and it would not make any noise in gear. It only does it when they make contact with the ground.

If so, that would eliminate the rear axle.

 

[jeepinwi]

My best guess would be some bearing(s) in the rear axle are trashed.

 

[xjhighroller]

I replaced all the bearings in it. wheel, pinion, and Carrier bearings. still the same noise.

 

[xjhighroller]

what can this be? as soon as I let off the brake and start rolling the knocking starts and become more pronounced with gas and speed. The wheels only turn about a quarter to a half rotation per every knock.

 

[j33pownr]

Here are a couple things I havent seen mentioned to narrow it down:
1) If it knocks at a really slow speed I would get someone to walk/jog along the side of the jeep to see which side and location the noise is comming from. Or you could get a video camera and some duct tape to narrow the search .
2) Also have you tried to reproduce the noise with the tranny in drive and the transfer case in neutral? Maybe the noise is in the case and not axle.
3) Does it make the noise in reverse as well?
4) If it still seems to be in the rear axle take the brake pads out of the drum and give it a test drive to see if they were rubbing. Look for wear on the drums to see if they scrape a rim or something weird.

I hope something helps because chasing gremlins sucks. I have been chasing a vibration at a certain rpm for a few months and have it down to either a crap ballancer or loose torque converter bolts. I dont think you have either being that you get no noise/vibs with the tranny in neutral and I do.

 

[xjhighroller]

So I finally figured it out after almost 2 months and a ton of money. The knock was the double Cardin cv on the driveline. I took it to the driveline shop twice too to have it checked and they told me that it was fine. I ran out of things that could cause the problem and decided to put the front driveline in the rear just to rule it out and today my dreams came true. No more knock

 

[Vanquish]

Wow.