CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

1994 Grand Cherokee making ruttle noise

Hello everyone,



I have this all wheeldrive, 8 cylinder, 5.2L that it just started to make this loud rattle, that vibrates the car. The sounds and vibrations almost feels coming from under my feet. I checked all fluids, transmission in particular is clear and do not smell burned. Transmission was completely rebuilt 2 years ago. The 2 front axles are 6 months old and the tires are 3 month old; at which time get aligned. The front stabilizer bar was just replaced as well. Checking and checking I discover that the front and rear differentials were very low in gear lubricant, and the transfer case was also very low in fluid. I fill all of them. I did notice a smoother drive but the original roar /vibration still there.



I checked all universals and driveshaft and all seems OK. At this point I run out of ideas… I was hopping that someone would give me some other ideas on what to check.



Many thanks and thank you for checking out my post!



Steven

Good Morning Everyone!

I am kind of surprised no one has a comment out there. Any ideas would be greatly appreciated.

First you referred to a vibration/rattle which makes me think that you should just look up under the car all around the exhaust system for a loose heat shield, though I wouldn’t expect that to vibrate the car.

Then you referred to it as a “roar/vibration,” and the roar part makes me wonder about wheel bearings. But if that comes with a distinct vibration you better deal with that asap (actually deal w/ it asap either way). Does the noise change/die down when you take a turn?

The only other thing I can say is not to necessarily trust the axles just b/c they’re old. I have had lots of problems with “new” axles, which are more often than not remans rather than new.

Thank you for your reply! Well, a mechanic friend of mine drove the car and concluded that the noise is a front differential noise! He suggested that it is easier to replace the entire front differential than to replaced the gears inside the differential… How is that possible? I think that he told me that because he has never changed the gears in one before. I know you still have to remove the two front axle in order to replace the gears but at least you are not removing out the entire front. Then, there is the cost of parts and side of them. A whole unit cost much more more than just the gear kit… Would you guys agree?

Your comments are greatly appreciated

As AA suggests, there is a considerable difference between a rattle and a roar, so either there are two separate problems, or the noise is not being described very clearly.

Anyway, here is a thought that came to me while I was in traffic a few minutes ago. I was driving behind a late model Dodge Durango that had apparently just been purchased as a used vehicle from a Nissan dealer.

As the Durango drove along, the spare–which is mounted beneath the rear of that vehicle–was visibly bouncing up and down on its tether. If the '94 Grand Cherokee has a similar placement of the spare, that is one possible situation to check, simply because noises can sometimes be telegraphed in such a way as to sound like they are coming from an area other than where they really originate. Of course, if the OP’s problem noise is actually a “roar”, and not a rattle, this suggestion will not help.

Revision: Now that you have posted that your mechanic suspects a bad front differential, that obviously eliminates the possible validity of my suggestion. However, if it is indeed the front differential, this does prove that noises can sometimes be telegraphed so that they appear to come from an area other than where they actually originate.

Ok guys, I am getting ready to proceed replacing the bearings.

As I mentioned at the beginning, I neglected to keep the front differential fill with fluid, so when I heard a roar from there I checked and it was almost dry and the little bit left smelled burned. So I am hopping I just need to replaced the bearings with the kit, and I was hopping someone could give me the steps on how to go about doing this. I have being told that I need to remove both axles; which I replaced about 6 months ago, so if that is the case, I have that part covered. Then I open the differential plate and I think that I supposed to remove the lock bolt securing the pinion mate shaft, then remove the pinion mate shaft, I understand pretty good up to here. There is something about a c ring which I do not understand yet, and then the actual removal of the bearings and seals with the bearing puller.

and installation of the new bearings and seals. Also, How can I determine if the gears are fine. Your help is super appreciated,

Steven