Clutch chatter

[kenb]

1998, 4.0L, AX-15, 125k miles

My new to me TJ has an issue with the clutch. I think it's what you would call chatter but I'm not 100% sure. It's not a noise but a jerking feeling when I'm slipping the clutch starting from a stop. The issue is only present when I'm actively slipping the clutch. Shifting gears while already moving is fine, driving in gear and idling in neutral are also fine.

The feeling is similar to trying to start with not enough gas. However, using additional throttle actually makes the issue worse. It seems to be minimized when using just slight pressure on the throttle to start. The feeling is about the same in 4WD as 2WD. Perhaps a bit less in 4WD. I think the issue improves when the clutch is warm although it by no means goes away.

Any ideas where to start with diagnosing this one? I've read a number of older posts on this issue but was having trouble sorting out which ones might be relevant to my situation. Any suggestions are appreciated.

Thanks,
Ken

 

[CharlesHS]

Do you know if the previous owner replaced the clutch recently ?
IF the clutch was replaced; was the flywheel replaced, was the the surface just scuffed or was the flywheel surface cut ?
The flywheel surface should never be cut; it has a slightly convex surface to promote clutch engagement.
IF the flywheel surface was scuffed there may have been hot spots that are still remaining which is causing the chattering feel.
LUK (edited) is the recommended manufacturer for clutch repair kits and flywheels since OEM is probably no longer available.

 

[kenb]

Thanks for the reply. I don't know if the clutch was recently (or ever) replaced. It looks like the skid plate hasn't been dropped in a while. The previous owner had it for several years but not many miles. It may have had this issue the entire time he owned it. I was hoping to avoid replacing the clutch but if I do I'll replace the flywheel in case that is the problem.

 

[TheBoogieman]

Mine acted similar to that before the master/slave cylinder went bad. I started thinking I forgot how to drive with a clutch. There was a shudder every time I took off. Eventually it started to stall when stopped with the clutch depressed, like the clutch was let out.

 

[TheBoogieman]

LUX is the recommended manufacturer for clutch repair kits and flywheels since OEM is probably no longer available.

LUK makes a better clutch, and it was the OEM kit used by Jeep.

 

[bluescapegoat]

Not exactly the same thing but my 05 and 06 both with the NSG370 and original clutch/flywheel have shuddered when letting the clutch out when it's raining for the duration of my ownership. I've owned a lot of manual transmission vehicles, many of them with more miles than the Jeeps, and the Jeeps are the only ones that have done that.

I've just kind of learned to work around it but it's an odd quirk.

 

[cpwolf]

Our 08 JK has this issue and the Clutch Slave is a problem.

It’s still there some, especially on hills, but my son has 3.21 I think axles and 35” BFG’s. So that doesn’t help the situation any.

I’ve got 4.56 that will go in sometime before he’s back from Europe in December (which means I’ll do it in November knowing me).

 

[CharlesHS]

LUK makes a better clutch, and it was the OEM kit used by Jeep.

Thanks to TBM and JB for the correcting the manufacturers name....

 

[macleanflood]

Swapping the clutch out in the TJ is a relatively easy job compared to other vehicles.

Swap it with a Luk...buy the kit on Amazon... flywheel isn't too much more.

My biggest complication when doing my clutch was all six of my frame nutserts were siezed. Go pull one of the skid plate bolts and decide if you need to order a set from Mr. B's Black Magic Brakes.

And the only specialized tool you need is a e-torx socket for the top two transmission bolts. You can get the pilot bearing out with bread and a punch.

-Mac

 

[TurboTJ]

If your drive shaft angle is too much due to a suspension lift or a tummy tuck it can cause this. I have a 2 inch lift and that caused no problems. Then I did a small (1 inch) tummy tuck and had chatter. A double Cardan shaft took care of that.

 

[kenb]

Thanks for the replies. I think I'm going to give it a thousand or so miles and see if and how the clutch behavior changes. It's good to know it's a manageable job if it needs doing.
This is a new to me Jeep. I just found an old oil change record and it appears it has been driven under a thousand miles a year for the past 15 years. I think it had sat since last summer before I bought it. Perhaps some additional miles will make it apparent if it's the clutch itself or the clutch hydraulics.

 

[Steel City 06]

Could the engine actually be pinging? On my canned tune, the engine lets out a few pings when I stab the throttle after a shift.

Be sure to inspect the motor mount and transmission mounts for excessive motion as well.

I did find that running a heavier flywheel smoothed out the shifting a lot on my NSG370.

 

[kenb]

I don't suspect it's an engine pinging issue. The problem doesn't manifest itself unless I'm slipping the clutch. If my foot is off the clutch I can give it full throttle acceleration and it's smooth.
Is there a guideline for how much motor and transmission mount movement is too much? I can certainly flex mine with a pry bar but it doesn't seem like they are broken.

 

[Steel City 06]

I don't suspect it's an engine pinging issue. The problem doesn't manifest itself unless I'm slipping the clutch. If my foot is off the clutch I can give it full throttle acceleration and it's smooth.
Is there a guideline for how much motor and transmission mount movement is too much? I can certainly flex mine with a pry bar but it doesn't seem like they are broken.

Generally you'll notice cracks in the rubber itself. As far as I know there isn't a definitive guide to how much movement is acceptable, but I would guess that if you felt like it had slack in it where there was no resistance in either direction, that would be indicative of a bad motor mount or transmission mount. The mounts are essentially rubber springs. So if you could rock the engine back and forth noticeably by pulling on it by hand, I would take a closer look. If it takes a prybar, odds are they are still fine.

 

[TheBoogieman]

Bad MM.

 

[kenb]

I got the old clutch out today and this is what it looked like. Whether or not that was the cause of my issues I guess it needed to be done. I'm putting in a new clutch kit and flywheel. Will see how it does once it's together.