Clutch Induced Vibration

[ccrank]

81 CJ7, power train is 258 I6 - SR4 - Dana 300 (yea, I 've heard a lot of the SR4 jokes)

I had my jeep torn apart for while putting a fuel injection system on with the associated new fuel lines, pumps, parts, stuff that makes these projects take too long. That part runs great, as long as the clutch pedal is depressed!

When the clutch pedal is released I get a significant vibration, almost a shudder, making a chattering noise that I can hear over the engine sounds. In fact it took me a while to correlate the vibration symptom to the postion of the clutch, thinking I had an interference problem after the MPI installation! The noise occurs in neutal and any gear, but the vehicle shifts and drives in all 4 forward gears and reverse. Depress the clutch and the noise/vibration disappears.

Reading through the Jeep Tech manual pointed to the trany shaft bearings, so I pulled the gear box and took it to a reputable gear shop, where they replaced the bearings (and synchronizers - I noted the GL5 comments in other posts looking for info before I wrote this one).

New shaft bearings didn't help. The guys at the gear shop don't/won't do any on-vehicle work (mostly they do piece-work for the local dealers) so I need some ideas where to look next.

Adjusting the play in the shift linkage seems to change the noise - taking up slack reduces the effect - but that makes sense as just a little clutch pedal travel will make the vibration/noise go away.

Any ideas where to look next?

 

[SteelHeadz]

There are several parts that may be involved in creating this noise and vibration.. since the noise and vibration changes with a clutch input it's Possibly a Pilot bearing or Throw out bearing failing and causing the noise.. The Vibration could be from Either the Pressure plate clutch disc or the main shaft.. A Chatter or Vibration while releasing the clutch indicates a Warped Flywheel..

 

[ccrank]

I made the original post some time ago. I thought someone might find it useful to share what I actualy found and how I resolved this issue.

Based on suggestion from SteelHeadz, I dropped the transmission, checked the flywheel, replaced most everything I didn't the first time in, put it all back together again (Yep, dropped the transmission again. See first post). Good suggestion, and good work was done, but didn't solve the problem.

Based on insight/inspection by my local mechanic, the problem seems to have been well-worn camshaft lobes (engine had 225K miles). When ever I released the clutch pedal (engaged the pressure plate), there was enough stress on the engine to make the camshaft walk back and forth, causing the vibration and tapping sound, sometimes at the front of the engine in the timing case, sometimes at the rear of the engine in the camshaft bearing. "Sometimes" meaning varied with RPM, but not nearly as often as each rotation.

Maybe this is all wrong, but replacing the camshaft, some new lifters and rods, other associated parts like springs and rockers (since everything was open), fixed the problem. Since the original post, I had a great season wheeling, and am running well this spring as well.

 

[SteelHeadz]

That makes sense and a good catch.

 

[yo momma yj]

a 3' piece of garden hose used as a stethoscope will PINPOINT noises should you hear anything else odd.