The Stovebolt Site Forums The Shop Area Driveline Throw out Bearing Clearance

1950 GMC 1/2 ton, stock 228 and 3 speed (column) transmission. Motor and transmission both completely rebuilt, with all new parts, including new clutch, pressure plate, and throw out bearing. I finally got the 3 on the tree shift box hooked up and adjusted on the steering column, so I have been able to take my truck for short rides up and down the dirt road I live on (full frame off resto, been working 5 years on it)! However, when I pulled back into my garage a few nights ago, while the truck was sitting there idling, all the sudden there was a whining noise coming from the flywheel/clutch area. I crawled under the truck while it was running, removed the flywheel dust covers, and think I pin pointed the noise from the new throw out bearing. One thing I noticed while looking up at the bearing, is that it was spinning even while the truck was not in gear. My question is, should the throw out bearing be spinning all the time even while the truck is in neutral? There is room for the bearing to slide back towards the rear (away from the clutch fingers) a little a more, so that it completely disengages the clutch fingers, but when I do that it throws my pedal free play adjustment off. Is the bearing supposed to stay in contact with the clutch fingers (no load though), or should I pull it back? Seems like there may be a fine line between keeping the bearing off the clutch fingers while keeping the pedal free play within specs. Note this a new (long) throw out bearing, that came with the clutch kit. Also note there is a brand new (New departure) pilot bearing in the back of the crank as well. Could this just be a bad/cheap throw out bearing?

When the clutch is engauged there should be some clearance between the brg. & the fingers. The free play spec is just aproxamit. There is variations between brands of clutches. As long as the brg. backs away from the fingers & the clutch releases before the pedal gets to the floor, you are good to go. Allow a little extra if possible as the brg. gets closer as the lining wears down.
George

I had an NORS throwout bearing start screeching on me. That was very annoying!

After adjusting the clutch free play rod to both ends of the bolt, I am still not able to completely disengage the throw out bearing from the clutch fingers. I did manage to get it to a spot where the bearing stopped chirping while in idle, but when I push the clutch in there is a brief chirp as I am pushing the pedal to the floor.

Also, notice in the attached photo, where the bearing rests on the transmission input shaft cover. There is still about 1/8 inch where the bearing could slide back. But now it seems like I have a new issue, oil leaking from the hole that's on the bottom on the input shaft cover. You can see about half of the hole in the picture, under one of the fork fingers. I am assuming this hole is not supposed to leak oil?

There are/were two lengths of release/throwout bearings. Perhaps your pressure plate needs the shorter bearing?

1 3/4" vs 1 7/8" length/height

Did you buy the clutch, pressure plate, and release bearing as a set?

That was my thought too. I did buy the clutch as a whole kit, so it came with the longer bearing. I am wondering if I swap them out though if that would give the me clearance I need.

If you bought it as part of a kit, it should be OK - unless it was mispacked by the supplier?

Clutch fork have a return spring on it?

ouh/ooh, BC59 - nice question (forgive this superfluous post)

There is a return spring on the pedal, is that what you are referring to? It’s new as well.

That's it, JakeM. Thanks

What about that hole? Can you tell me any more about that?should it be seeping oil?

The hole in the front bearing retainer is there in case any oil gets past the oil slinger, it will just run down the bellhousing.
This prevents it from dripping oil from the front of the tube. If it dripped out the front it would get on the clutch.

Could you post a photo showing the fingers on the clutch. If the fingers are recessed in the housing & are near parallel with the flywheel it takes the long brg. If the fingers are extended out to about the outer surface of the clutch, it takes the short brg. Those older trans. had no front seal. They used a slinger to keep the oil back. If the trans. is too full or slanting foreward the grease can leak out & drain from that hole.

I will try and get a photo tonight when I get home from work. I will also pull the paper work and receipt from the clutch kit. I’ve had the tranny and clutch on the truck for over a year and a half now, and I’ve never had any of these issues while running they truck at idle for 10-20 minutes at a time over that time. The issues (chirping and seeping oil) started after I was finally able to hook up the shift box, and take the truck down the road for a drive. Either way I’ll post that info tonight.

Also one other thing I noticed when looking up at that hole while the truck was running, I can see the transmission shaft spinning in that hole while the truck is in neutral, then when the clutch is pushed it stops spinning. I am assuming this is correct right, that shaft will be spinning in neutral, but no power is being transferred. Just wanted to double check.

That will pull the pedal back by there should be a spring to pull the clutch fork back as well.

I can't get a better picture of the clutch fingers without pulling the transmission, which I may do in the next few days.

The clutch kit I got is Sachs K1042-01, and seems to be a pretty common kit for these trucks and early 50's Bel Aires. So I am sure the bearing is the correct one. I think its just a bad bearing that I have. I am going to pull it off and take back to the store I bought it from. The kit has a lifetime warranty.

As far as a return spring for the fork, my truck definitely does not have one. I didn't pull one off when I initially pulled the clutch off, and there is no mention of one in the GMC factory manual. I'm not even sure a return spring on that would do any good. There is no way for a spring to pull it back as I can see. The fork is connected ridgedly (if that's a word) to the adjustment bolt, so I cant picture how that would work.

I'll try to get out & take a look my '49 GMC in the pasture.

Yes, it would spin, then stop when clutch is disengaged. But that's a good way to get run over under there. I think BC59 is correct. Oldtruckmanual project does not mention a fork return spring BUT I see one in the picture! Big and long. You need that.
If the throwout bearing has a slight preload against clutch, it will spin all the time. That is OK. Noise is not OK. either bad throwout bearing or transmission bearing. Does noise stop when clutch is disengaged? Can you stop noise with rod adjustment (forget the pedal freeplay for this test). Don't do any of this adjustment/testing while under truck and set parking brake, etc.

Bartamos can you post a picture of the spring?

I mentioned in a previous post that I can not stop the noise with adjustment of the rod. I’ve moved it to both extreme ends of the rod.

I think it’s just a bad bearing. However I am still getting mixed answers on whether the bearing should be touching the clutch fingers or not. Some say yes it’s ok, others say no. Since I can’t get it off the fingers, I am assuming with this particular kit it’s ok for it to touch, but without load.

If the bearing touches the clutch fingers it is going to spin, so no it should have enough clearance to unload itself completely away from the clutch fingers. I believe some late model ford engines have the throwout bearing spinning and it is normal for them but not our trucks and trans,.