Wrangler guys - got a new shudder

99 TJ, 4.0L, 207K miles
I noticed yesterday that I have a shudder when I release the clutch from a stop and when I turn the engine off. It's a deep, "thunking" sound. Otherwise I don't feel or hear anything when going through the gears while driving. Just when starting from a complete stop and when the engine gets turned off. It feels like it's coming from the front half of the Jeep, not the rear end.

I'm thinking maybe a motor mount is bad? It's snowing like hell and the driveway is a mud pit so I'm not diving under there today. Just thought I'd throw it out there to get some ideas on what else to look at when I do.

Definitely start with the motor mounts.

Quote:

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Originally Posted by newracer

Definitely start with the motor mounts.

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Then work back, looking at the transmission and drive shaft mounts.

Also take a look at all the exhaust, cat and, muffler mounting brackets & isolators.

easy
Just
Empty
Every
Pocket

Solid advice on the first 3

you can see the rubber in the motor mounts from the top. No need to crawl under.

From your description, I'm guessing the chain slapping around in your np231.

I also had a shudder from a stop in an old toyota I used to have. The flywheel was starting to glaze. Replaced that and the clutch while in there and it fixed it.

"Shudder" sound like a clutch issue If its been a long time since the clutch has been replaced that may be the problem. A way to check engine mounts is to open the hood, sit in the drivers seat and find an angle to see the engine. Then push in the clutch, put your heel of the other foot the brake, reach over with your toe and give it some gas, slowly release the clutch, if the engine looks like it is trying to jump out of the engine compartment, the mounts are broke. If there is no abnormal movement they should be good. also with a clutch a new remanufactured clutch can tend to cause "shudder" for that reason I always spend the extra and get a new one.

An easy test for the clutch is to:

Put on the emergency brake.
Put into 1st gear.
Right foot gives gas while the left foot slowly releases the clutch.

If the tach stutters and jumps, there may be a clutch/flywheel issue. If the motor promptly dies, the clutch is probably alright.

There was no rubber left on the driver side motor mount, when I replaced mine. It didn't make any noise though.

Does it make the "clunk" sound if the trans is in neutral when turned off?

Update:
Motor mounts look fine. Exhaust looks fine. Shudder still happening but doesn't seem to be getting worse.

But wait! There's more!

I started getting a NEW noise: sounded just like squealers touching a rotor, seemed to be coming from the front passenger side. Not squeeling, but a metal on metal rubbing noise that has nothing to do with engine RPMs, but goes away when going slow (under 20MPH), so I know it's not a alternator or water pump bearing going to shit. Took the wheel off...brakes are in awesome shape. Dust cover not rubbing anywhere either. So I check for a bad wheel bearing and it's got some wiggle up and down. Not real bad, but there really should be NO wiggle up/down. So I replaced the hub thinking that's it. No dice. Now I'm running out of ideas and $75 poorer.

Then it snows tonight like a somabitch and I have to go into 4WD. Yet another not good noise. Squeeling from another location (TC I guess?) and an angry sounding Heep. Anger goes away when I take it out of 4WD but the "rotor squealing" sound remains.

I guess I'll look at all the u-joints up front and maybe open up the front diff to see what's up asap. I have to think this is all related somehow. Hopefully just a bad u-joint that gets even more pissed when it's under additional stress in 4WD. Any other suggestions?

It could be your axle U-joints. With your fixed hubs, the axle/u-joints are always spinning and could definitely squeal.