4.0 gonna blow?

[Joopin]

For the past couple weeks I have been observing the new noises coming from my jeep (91 4.0 5spd.). It started on the way back from Atlantic City the first weekend of Dec. It is difficult to describe the noise but here it goes...

it's a whine, and grinding/chattering

But it only happens in top end of 3rd gear and all of 4th and 5th. It also only makes the noise when I have my foot on the gas, when I let it off the noise goes away. When I downshift the noise goes away. I can "feel the noise" through the shifter too.

My thoughts are that the inner bearings are starting to go... but this is just a guess. The rear main went over 2 years ago, but I didn't fix it right away and I heard that not fixing it right away can lead to the inner bearings to get loose. But it was that then wouldn't the noise happen as long as the engine is running? I'm wondering if the 4.0 is on it's last legs, it does have almost 212k on it...

 

[Sparky-Watts]

I dunno....sounds like when my transmission let go in my Toyota....3rd, 4th, and 5th gears started to whine and chatter, then one day BANG!!!! It was gone.....

 

[Craig]

I was thinking the same thing of my 4.0L two weeks ago. Sounded like really loud lifters, not the usual lifter noise you get from these 4.0L's but really loud. Got faster as the rpm's got higher. Held a stethascope to the motor to try and figure out where it was coming from and couldn't because it was resignating through everything. We narrowed it down to a bearing in the front of the motor. Started with the tensioner pulley (for my compressor), not that. Did the water pump, not that. Bypassed the compressor with a stock serpentine belt, not that. Ended up being a bad bearing in the power steering pump.

 

[Joopin]

I was thinking the same thing of my 4.0L two weeks ago. Sounded like really loud lifters, not the usual lifter noise you get from these 4.0L's but really loud. Got faster as the rpm's got higher. Held a stethascope to the motor to try and figure out where it was coming from and couldn't because it was resignating through everything. We narrowed it down to a bearing in the front of the motor. Started with the tensioner pulley (for my compressor), not that. Did the water pump, not that. Bypassed the compressor with a stock serpentine belt, not that. Ended up being a bad bearing in the power steering pump.

So you used the Stethescope to narrow it down to the bad bearing? Or did you have to take all that off and check everything. That would be great if it was something small like that, now to find a stethescope. Thanks for the idea!!!

Joop

 

[Sparky-Watts]

now to find a stethescope. Thanks for the idea!!!

Joop

A long handled screwdriver works just as well. Put the tip against the suspect part, and the handle against your ear.

 

[Junkpile]

A wooden broom handle cut to a manageable length works too.

 

[OutOfStep]

I had a cam go on me, it had similar symptoms before tshtf

 

[Craig]

You can buy a mechanic's stethascope which has a long tube on the end instead of a round thing like a doctor's. You can find them at autoparts stores. It works pretty good for finding squeaks and noises under the hood. Didn't do too much good this time because the noise was so bad and the bearing was so far gone that it was vibrating and the sound was being transmitted through everything. Just started replacing things starting with the cheapest.