Clutch grind

[Flex BT]

I just got my '81 CJ a few weeks ago. I've learned a ton from this site already so thanks.

It doesn't always happen, but most of the time when shifting a grinding / vibrating happens when I'm bringing the clutch back up and it stops when the clutch is fully released. The PO told me he had a new clutch professionally installed, is this a clutch issue or Transmission ? I think it's a T-4 in there but I'm not sure. I changed the Transmission oil today which came out looking pretty clean. I put in a quart of synchromesh and a quart of ATF and it didn't make any difference. I thought I read that the Transmission took 6.5 pints but it was overflowing after just the two quarts. In any case, it didn't make any difference whatsoever. Any ideas on the cause of the grind and how to fix it?

 

[CJ]

Just sounds to me like you need to adjust the clutch. How far down do you press the pedal until the clutch releases and how far up until it engages? What is the distance you have from the engage until the top of the stroke?

 

[Flex BT]

I'm not sure on the release point since I always slam it down to the floor before shifting. Once I've selected the new gear it moves quite a ways up before the point it starts engaging (and grinding in most gears).

 

[jeffgtoman]

It sounds to me like you're getting clutch chatter? It would make some noise and vibrate the Jeep quite a bit. Does it get worse when you apply more gas pedal during a shift?

Several things can cause clutch chatter which is more common for your description than gear grinding.

1. Clutch disc put in backwards. Sometimes this isn't even possible because of the thickness on one side of the disc.

2. Clutch disc contaminated with oil or hardened due to overheat.

3. Clutch disc has that overseas disease. (Made In China.)

Try letting the clutch out on level ground or facing downhill without giving it any gas. Do this in first gear and you can even try it in low range. Does the clutch release smooth without and vibration?

The whole point of the clutch disc is to slip smoothly while the Transmission speed catches up with the engine speed. When there is something wrong with the clutch disc, it will chatter and vibrate instead of slipping smoothly. It would vibrate the most taking off from a dead stop with the engine revved up.

If you've driven around with no clutch free-play, you could have been slipping the clutch which would overheat it and cause it to chatter. The only fix is a new clutch and pressure plate and a proper clutch adjustment. The flywheel also needs to be resurfaced if there is any damage to it.

Also check the free-play now to see if it is adjusted correctly. It won't fix your problem but it is a clue to what caused the problem. You should be able to push the clutch pedal down about 1/2 inch with 2 fingertips. It will bounce back up from the tension of the return spring.

 

[Flex BT]

I'm at work all day today unfortunately, I should be able to give all your suggestions a shot tomorrow afternoon.

It does seem more like a vibration than grinding that increases with more gas but it usually doesn't happen noticably in first gear. This may be because I don't hit the gas very hard while going into first and it's usually revved higher when going to the other gears.

 

[CRETE4U]

Mine vibrates a little too when I let off in first gear. I'm not too worried about it. I never slip the clutch in any gear but first. I've had clutches that chatter. That would need to be fixed.

 

[Flex BT]

Here's my results...

I am able to push the clutch in about 2" using only my fingers. It returns to the original position.

From a stop / slight roll I can move the jeep into first with little to no gas and it does vibrate, although not terribly. When I have my foot on the gas going to 2nd it vibrates a whole lot depending on how much gas I'm giving it.

Does it sound like I'm going to need to drop the tranny and replace the clutch disc? What else should I be replacing while I'm in there? I've never removed a Transmission before but I didn't get the jeep to send it off to a shop.

Here's what the blue beast looks like. Much uglier in person / close up. Whoever painted it didn't do a great job of rust removal so the paint is bubbling all over. I'm hoping I can get everything running good enough to justify a new top and fiberglass body some day.

 

[mtnwhlr]

The vibration or I like to call it a bad shake is from the springs in the clutch disk getting old and loose. When you do a clutch you want to replace the disc, pressure plate, throw out bearing, pilot bushing and get you flywheel turned. After getting it back together you want to adjust it so you have only 1'' of free play at the top.

 

[jeffgtoman]

The vibration or I like to call it a bad shake is from the springs in the clutch disk getting old and loose. When you do a clutch you want to replace the disc, pressure plate, throw out bearing, pilot bushing and get you flywheel turned. After getting it back together you want to adjust it so you have only 1'' of free play at the top.

I agree with this.