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post #1 of 12 Old 04-16-2017, 01:56 PM Thread Starter
spiydr
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Grinding on acceleration

I have been trying to narrow down where the grinding or growling sound is coming from for the last few days. It appears to originate from the front of the vehicle but only on hard acceleration. So far I have replaced both front axle u-joints and hub assemblies. While there was a toasted u-joint it did not solve my issue. It did seem to lessen the extent of the grinding though. Today I decided to remove the front drive shaft in order to eliminate it as the culprit. That helped a bit but if I try hard enough I can still get the sound to occur.

After removing the front drive shaft I grabbed the yoke on the front diff and noticed it had a bit of play when twisting back and forth, is that normal? I can twist a quarter of an inch in either direction before it clicks.

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post #2 of 12 Old 04-16-2017, 04:02 PM
CJ7-Tim
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A grinding noise, or a rattle noise ? Have you inspected the rear drive shaft u-joints, the engine and transmission mounts, and the exhaust system and exhaust hangers for loose parts or contact with the body/frame ?


A generous amount of free rotation of the pinion yoke is normal.

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post #3 of 12 Old 04-16-2017, 05:02 PM Thread Starter
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Definitely a grinding noise.

I did do a visual inspection of the rear u-joints as well as grabbing the drive shaft to see if there was play. It seems fine but I will be dropping it soon to replace u-joints anyway.

The exhaust hangers look good and nothing appears to be contacting the body. Honestly I cant tell by looking at the transmission or engine mounts if they are good or not. I did read that some have reported contact between the radiator fan and the radiator due to bad mounts but I see no evidence of it.

Could a stretched out chain in a transfer case cause this? Would it still happen even in 2WD with the front drive shaft disconnected?
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post #4 of 12 Old 04-16-2017, 05:12 PM Thread Starter
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I did a little reading on the transfer case and if it was the chain it would be more of a popping sound. Not to mention with the front drive shaft disconnected and in 2WD the chain doesn't move. At least as far as I understand it.

Last edited by spiydr; 04-16-2017 at 05:33 PM.
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post #5 of 12 Old 04-16-2017, 05:38 PM
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A worn out T-Case chain makes popping noises in 4wd.

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post #6 of 12 Old 04-16-2017, 09:00 PM
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Transmission mount. One of the exhaust hangers is mounted to the transmission mount, and this forces the exhaust pipe into contact with the crossmember when a worn out transmission mount allows the rear of the transmission to droop too far under heavy acceleration. It took me quite a while to figure out what was causing this noise on mine, and a new mount fixed the noise. The mount tends to get pretty badly soaked in oil if you have (or have had) an oil leak on the engine or transmission, due to the oil flowing back during driving. The oil breaks down the rubber in the mount, resulting in the rubber being extremely soft and spongy.

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post #7 of 12 Old 04-17-2017, 07:21 AM Thread Starter
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Quote:
Originally Posted by KF4SQB View Post
Transmission mount. One of the exhaust hangers is mounted to the transmission mount, and this forces the exhaust pipe into contact with the crossmember when a worn out transmission mount allows the rear of the transmission to droop too far under heavy acceleration. It took me quite a while to figure out what was causing this noise on mine, and a new mount fixed the noise. The mount tends to get pretty badly soaked in oil if you have (or have had) an oil leak on the engine or transmission, due to the oil flowing back during driving. The oil breaks down the rubber in the mount, resulting in the rubber being extremely soft and spongy.
I will take a closer look and see if that's the issue.
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post #8 of 12 Old 04-17-2017, 07:35 AM
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Quote:
Originally Posted by spiydr View Post
I will take a closer look and see if that's the issue.
There is little clearance there as you can see.

Also, engine mounts can contribute to the issue.
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Transmission Mount Bracket.jpg  

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post #9 of 12 Old 04-17-2017, 07:46 AM Thread Starter
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I will definitely be crawling under there later today. Would be awesome if that's all it was.
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post #10 of 12 Old 04-17-2017, 07:56 AM
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We need a good comparison photo of good versus bad engine mounts.

Anyone have any?

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post #11 of 12 Old 04-18-2017, 08:07 AM Thread Starter
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The mount looks good and there are no signs of contact between the exhaust and the cross member. Tomorrow I plan to replace the fluids in the tranny and transfer case. Hopefully I don't find any metal shavings.
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post #12 of 12 Old 04-18-2017, 12:04 PM Thread Starter
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New symptom. When coming to a stop there is a binding noise when under 5 MPH. Kind of like something is winding up and letting loose every quarter second or so. It feels and sounds like its coming from up front (diff maybe). Which coincidentally is where the grinding noise is coming from.

Guess I need to pull the diff cover and take a look inside.

Last edited by spiydr; 04-18-2017 at 12:29 PM.
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