Throwout bearing problem?

[CAROLINA CUMMINS]

Hey guys,



I have been pretty quiet here lately. I did manage to get a 3200rpm gov spring and piston lift pump installed Man, this thing will roll now:-laf Anyways, back to the scheduled program, that'll hafta be a diff thread



I've been having problems with my throwout bearing, it has been rattling for the past 1000mi or so. It's only gotten real bad here lately, it's starting to squeal after extended driving but will immediately go away when the clutch pedal is pressed. OK R&R no big problem, but I need to figure out why it failed in 40,000mi?; before I replace it.



I try top extend the life of throwout bearings by leaving my foot off the clutch pedal at stoplight, in everything I drive. So that didn't seem to be the problem; but I crawled under the truck and it IS running all the time I have to move the clutch fork maybe 1/2" before it will stop. I understood that throwout bearings were not supposed to run while the clutch pedal was released. It's kinda hard to see on my 2nd gen, so hard to tell there.



What could cause it to run all the time? Wrong pressure plate/clutch? Flywheel ground too much?? Clutch is a SBC Rally, it was put in and flywheel ground about 40,000mi ago. Just want to get it figured out before I install and wear out another one.



Thanks, Steven

 

[PToombs]

It could be air in the slave cylinder. When you push the clutch, it compresses, then when you let off it expands and holds the bearing in?

The only other thing I can think of is improper install?

 

[CAROLINA CUMMINS]

Hmmm, I'll have to check on the air in the slave cylinder. thanks



I did the install. I could have missed something, but haven't had any problems before. I guess I'll see when I pull it out, hopefully. Any more ideas??



Steven

 

[NIsaacs]

Doesn't the throwout brg. always turn with a hydraulic release system? That is why they never need adjusting, they self adjust. As the clutch fingers push the brg. back on release, the slave cylinder will self center at that point. As the clutch wears, the brg. stops sooner, thus the slave cylinder picks a new self centering position. Or am I all wet?





"NICK"

 

[CAROLINA CUMMINS]

TTT



Well, I found out this evening what the problem is. I chased down the squeal to the front of the engine. Looks to be A/C clutch pulley.

Anyway, I got to thinking; what could possibly be wrong that would cause clutch/throwout bearing problems and a squeal @ the front of the engine that goes away when you press on the clutch Only one possible thing connects the two. Sure enough. the crank has about 1/4" play in it I was hoping against it, but I'm glad I found out what it was. Looks like I'll be putting in some thrust bearingspretty soon. Hope that's all



thanks for the input guys



Steven

 

[1stgen4evr]

Mark H Or is that MarkH did a thrust bearing in 'frame'. Quite a chore but do-able. You might want to PM him for any tips. I think he did some pics as well.



James

 

[Don Tanklage]

anyone else think that by a time the crank ends up with a 1/4 inch of end play that maybe there are other bearings n such that ought to be looked at?



don

 

[PToombs]

If it has a 1/4 inch of play, I think you're into the block. If not, you are darned close. Not what you want to hear, but you might want to pull it for this. I think it's going to be more than thrust bearings. :{

I hope I'm wrong!

 

[1stgen4evr]

- - - -ought to be looked at?- - -- -



Oh for sure, by the time you see the thrust bearing, you will have seen lots of other things. But in fact, it may only require a new thrust bearing. It is a real pita however you go at it. Pulling the engine is a heck of a chore and in frame is also a tough trip. I would look at all the lower mains. I cringe just thinking about it. I hate wrenching with a passion. Did so much of it when I was younger. Now days, if it ain't broke, I don't fix it.



James

 

[DEdds]

Hey Carolina, Has your truck had a hard previous life before you got it. I'm just curious. I worry about such occurences in my truck now she is getting up there in mileage.

 

[CAROLINA CUMMINS]

Hmm, no it's not had an excessively hard life. My grandpa bought it brand new; and I've had it the last seven or so years. It has been worked, but what pickup hasn't?



Not sure how long this has been an issue though. Just recently have had clutch disengagement issues. I hope it hasn't got the block yet. My 1/4" guesstimation could be wrong, I haven't pulled the ruler or dial indicator out yet, but I will It could get right interestin'





Steven

 

[GCroyle]

Clutch Bearing Freeplay

Sorry to hear about the crank endplay, that doesn't sound good but I can't offer much more that that.



Just to help understand what is going on, the clutch release bearing on these trucks (and most all modern applications) does not have freeplay. Freeplay will be defined as the bearing being pulled away from the diaphragm fingers and the bearing is no longer contacting and turning.



The slave cylinder has a spring inside it that pushes on the fork and this creates a preloaded bearing that turns the entire time the engine is turning. If you want to disprove this, please post a picture of the RETURN spring necessary to pull the beating back away from the spring tips. If we know how it works, we can all do a better job of diagnosing.

 

[1stgen4evr]

- - - - a spring inside it that pushes on the fork - - - - -



I thought that but have not had the occasion or problem that required a look inside the slave cylinder.



I ALWAYS replace the throwout brg when I am down that far. I did think that the brg turned all the time even though I suppose it is very lightly loaded except when the clutch is depressed.



Some people ride the clutch with their foot. That will definitely shorten the life of the throwout brg.



Good luck Steve



James