Possible YJ Clutch Slipping - JeepForum.com
 
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post #1 of 9 Old 05-04-2021, 04:04 PM Thread Starter
alexs93
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Possible YJ Clutch Slipping

Backstory on the YJ:

'94 YJ, 4.0, AX-15 It sat in one of my dad's coworker's barn for maybe 10 years or so. About a year ago I got it up and running: new clutch, throwout bearing, pressure plate, slave/master, engine/trans mounts, brake lines, fuel filter, u-joints, CAD delete with XJ shafts, complete exhaust from front to back, dist cap, rotor, plugs and wires, BDS lift, you name it and it was replaced.

Since getting it back on the road I've put about 3000 miles on it. Driving today about 30 minutes into a 35 minute drive, I felt what seemed like the clutch slipping (4th gear about 50mph) that lasted all of 1.5 seconds and then it was back to normal. Pulling into the neighborhood in 2nd gear I had the gas pedal almost to the floor and it was stumbling and couldn't get out of its own way.

I drove to a steep hill to see if the clutch was in fact slipping, came to a complete stop, put it in first and let the clutch out and it pulled right up the hill. When I got to the top of the hill I shifted to second and floored it, it stumbled and sounded like it wanted to backfire. I couldn't quite tell if it was a backfire/misfire noise, or a "mechanical" noise.

I had my dad come over about an hour and a half later to ride with me to listen to see what he thought. Before we rode around we were power braking to see if the stumbling under heavy load would happen in the driveway, but nothing. As a matter of fact the clutch started to lightly smoke well before stalling during the power brake. We went out for a ride, but the stumbling and mystery noise didn't happen. I noticed that it still lacked the power that it should have had at high revs, but it wasn't stumbling as bad as earlier in the afternoon. Pulled in the driveway and put it in 1st and let the clutch out to see if I could feel clutch slipping and it felt fine. Dumping the clutch also grabbed hard enough to throw gravel.

I can't help but wonder if something got on the clutch disc or flywheel and burned off during the power braking. When replacing the clutch I didn't notice any leak from the trans seal. There is a slight RMS leak, but it's nowhere near as bad as it could be.

Thoughts? Questions?

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post #2 of 9 Old 05-04-2021, 05:05 PM
Boojo35
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A slipping clutch will not create a stumble or close to backfire condition. A slipping clutch will create a condition where the engine RPMs are higher than normal in a given condition.

A clutch that is overly grabby may do what you say. If the Jeep has sat a while, the input shaft splines may be rusty and the clutch disc binds on that. It may free up with driving but the right cure is to clean the hell out of the input shaft and use a very light coating of grease (and I mean very light coating because anything more will send grease across your flywheel and clutch through centrifugal force. Grease will destroy your clutch. ).

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #3 of 9 Old 05-04-2021, 05:09 PM Thread Starter
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Quote:
Originally Posted by Boojo35 View Post
A slipping clutch will not create a stumble or close to backfire condition. A slipping clutch will create a condition where the engine RPMs are higher than normal in a given condition.

A clutch that is overly grabby may do what you say. If the Jeep has sat a while, the input shaft splines may be rusty and the clutch disc binds on that. It may free up with driving but the right cure is to clean the hell out of the input shaft and use a very light coating of grease (and I mean very light coating because anything more will send grease across your flywheel and clutch through centrifugal force. Grease will destroy your clutch. ).
Input shaft was cleaned and greased when clutch and bearings were installed.

Now that you mention it, it makes sense that a slipping clutch would just over rev the engine rather than bog it down.
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post #4 of 9 Old 05-04-2021, 05:20 PM Thread Starter
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Also, maybe "bogging down" isn't the best way to phrase. How about it's not pulling as hard as it should under heavy throttle.
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post #5 of 9 Old 05-04-2021, 05:25 PM
fishadventure
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Drigas. How long has ethynul gas been in it, sitting?
Fuel filter.
Make sure the ASD and fuel pump relays are seated
Check for vacuum leaks
Check cat for being plugged

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #6 of 9 Old 05-04-2021, 06:02 PM Thread Starter
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Quote:
Originally Posted by fishadventure View Post
Drigas. How long has ethynul gas been in it, sitting?
Fuel filter.
Make sure the ASD and fuel pump relays are seated
Check for vacuum leaks
Check cat for being plugged
Gas tank was dropped, emptied, some seals replaced, fuel filter and rubber line replaced during rebuild.

It gets driven to work everyday that it's not raining so I don't think stagnant gas is the cause.

Relays are seated correctly.

Most vacuum lines were replaced during rebuild if it was suspect and the usual cracked elbows were also replaced. I looked them over this afternoon and there was nothing that stuck out.

Cat was a brand new walker during rebuild, but it's possible that it's plugged. It was actual one of my first ideas since it happened so suddenly. Since I dont have to do emissions I was considering taking it out to see if that makes a difference and just leaving it out either way.
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post #7 of 9 Old 05-04-2021, 06:07 PM Thread Starter
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Only reason I'm hesitant to point fingers at the cat is that it only happens under hard acceleration. I can sit in the driveway and take it to the rev limiter with no problem.
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post #8 of 9 Old Yesterday, 02:42 PM Thread Starter
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Fuel pressure was 30-32 psi with regulator plugged in and 40psi with regulator disconnected. Ignition coil was 1.1ohm for primary, but 9.38k ohm for secondary. I'm going to go ahead and replace the coil and see what happens.

I know this isn't a very exciting thread, but I appreciate when others report back with closure when I find an old thread.
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post #9 of 9 Old Yesterday, 03:16 PM Thread Starter
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Brought my meter with me to advance and the coil they sold me had the same measurements so I went ahead and returned it. No sense in replacing it with one that measures the same.

Gonna keep digging tonight.
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