Clutch / throwout bearing / probably transmission problem

231 v6/SM465/D18 combo, only ever really driven in low range off road.

A while back my jeep started acting up. I'm getting a loud but low pitch grinding noise out of the transmission / bellhousing area and it wants to creep forward with the clutch out and the transmission in neutral. I ended up pulling the transmission out and finding an obviously bad throw out bearing, figured that was likely the problem and put it back together with a new one. At the same time i looked into the bellhousing with a flashlight and the pilot bearing felt good spinning it with my finger, no sign of it seizing up on the input shaft or anything. Needless to say when I got it all back together my problem was still there.

If I sit with it idling in neutral with the clutch out, it continuously makes the noise. When I push the clutch in, I can hear whatever it is slowly spin to a stop and stop making noise. Which tells me it's something spinning in the transmission if it's not moving when I have the clutch in. The oil in the transmission has a definite shiny metal color to it. I'm about to pull it back out to see what I can find. Any idea what specifically to expect? I'd like to think it might be the transmission input bearing, but I'm thinking it would have to be the bearings between the input shaft and main shaft or something to make it want to drive forwards in neutral? To further complicate things, I had a somewhat suspect shop rebuild the transmission 3 years (but only 50 miles) ago with new bearings and a new novak mainshaft.

As possibly a side note, the bad throwout bearing that I just replaced had less than 1k miles on it when I took it out. I'm thinking it failed because I had it set up so that it spun 100% of the time and it's probably not rated for that. But I suppose a bad input bearing could contribute to a quick failure of the throwout bearing as well? When I set up my clutch slave cylinder, how much free space do I need to leave between the throwout bearing and the clutch pressure plate to assure they don't touch all the time?

 

If you just had the SM465 rebuilt I would think it would be bullet proof. I rebuilt mine 7 years ago, still going strong. As for the grinding noise? Not sure. I can explain winning coming from the transmission. Not grinding. Now when you said. Spinning the pilot bushing with your finger. The pilot bushing should be pressed into the crank. Or do you have a pilot bearing?
The hydraulic clutch should be adjusted so there is free play on the throw out bearing.

 

Yup, clutch not releasing fully or pilot bearing/bushing sticky. The other possibility is the bellhousing is distorted not allowing the transmission input to run true to the crankshaft. Any angle will cause the pilot bearing to bind on the input. Can be checked with a dial indicator. This will cause excessive wear on the input bearing, main drive gear to mainshaft pocket bearings, etc. plus the main drive gear won't be running true to the cluster gear causing metal shavings. Just something to consider although not common.
You might contact the shop that did the work. They may follow through with a warranty even though its been so long. The shop I contract for has warrantied years after purchase if it was an obvious shop issue and the trans was obviously not run much. Any good rebuilder should be able to tell this as long as water, debris, or abuse hasn't occurred.

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I do have a pilot bearing, so I was able to move it with my finger, and it visually still looked 100% new. Literally all of these parts (clutch, pilot bearing, throwout bearing, rebuild parts on the transmission) are all but new, which leads me to worry about something being set up or installed wrong. Or maybe a distorted bellhousing. The pilot bearing is made up of like a cage of needle bearings, so I imagine if there was an alignment issue with it or it seizing to the input shaft there would probably be visible damage or play in the bearing? I haven't ruled out my premature throwout bearing failure to an alignment issue either...

If the clutch wasn't releasing fully, would the jeep still try and drive forwards even with the transmission in neutral? I'm not trying to discount what you're saying, just trying to wrap my head around this. I feel like I have so many clues, I just can't make sense of them.

Here's a video of it making the noise, you can hear it starting right at the beginning, and it goes silent every time I have the clutch pedal pressed in.
http://youtu.be/o8oIhUmm3xw

I've got tomorrow off work, so I'm going to pull the trans first thing. I'll definitely throw a dial indicator on the input shaft and see if I can come up with anything.

 

Is it hard to get into gear? If not then probably not a clutch or bellhousing issue. Another thought, is it possible the nut holding the transfer case input gear on has come loose? Have seen this before and depending on which adapter/mainshaft you have (there are different ones for the 465) it's possible if this nut is loose the mainshaft could be walking forward causing the problem you describe.


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Every now and then it kind of "binds up" and is difficult to shift, but it usually keeps me from getting it out of gear, not into gear. And it does it very rarely, I wheeled a whole weekend at moonrocks and it never did it.

I've got the 1" thick novak adapter/mainshaft, that's a good idea about the nut coming loose.

 

Thought I would fill you guys in on the mystery problem. When I had the trans rebuilt the guy used the new 1st gear bushing from the novak rebuild kit which is for a pre 1978 transmission. The thrust washer that goes with it is supposed to measure 0.197" thick, but he reused the thrust washer from the newer donor transmission which measures 0.187" thick. So the transmission had 10 thousandths too much end play.

I put in the correct thrust washer and a new pilot bushing and it got rid of 75% of my noise and now it shifts correctly and doesn't try to creep forwards in neutral. It still sounds like hell, but I'll probably run it for another year or two until I get sick of it and then throw another rebuild kit at it.

At any rate, thanks for trying to make sense of my ramblings.