Throwout bearing?

[JDiehl]

It's been really cold here and I try not to use the parking brake after driving in the snow and rain. Other morning put the truck in low with the clutch fully depressed and made the truck rock. The rocking was almost unnoticeable so I took the truck out of gear again pressed the clutch in and had the same result. Could it be the cold temps or something more sinister? Truck has 29K.

 

[B.G. Smith]

Not sure I understand exactly what you are saying, does the truck "rock" by just depresssing the clutch or is it when the transmission is in gear? Could the rear tires be frozen to the ground? bg

 

[JDiehl]

Truck rocks as I move the gear shifter into gear. Rolls forward as the shifter is moving then truck rolls back to the original position once in gear. Don't think the wheels are froze down as it 's done it also in the heated bays (60 deg) at work.

 

[B.G. Smith]

Ok, I understand. Sounds like the clutch is dragging just enough to keep the transmission input shaft turning when pedal is depressed, which you have already figured out. I wouldn't think the cold weather would cause that. It could be a problem with the clutch master cylinder or slave cylinder I suppose but with the low mileage doesn't seem likely. It could be the pilot bearing in the flywheel binding up just enough to cause the clutch to not stop spinning??? Does it still do this after the engine is up to operating temperatures? bg

 

[DE Jeeper]

My dd does this expecially when going in reverse. I think its normal for my clutch. I would guess failing hydros would be the first place to look for you, but not sure I would worry about it unless shifting is effected.



Aaron

 

[JDiehl]

It shifts fine once every thing is nice and warm. The second to third is rough first thing in the morning.



Should I take it in and get it looked over. Will it make other components fail later?

 

[RPosey]

My 2 cents, I think it is the friction of the turning gear/gears and the cold transmission oil.

 

[B.G. Smith]

The only gears that would be turning with the clutch engaged and engine running would be input gear, cluster gear and reverse idler if transmission is in neutral, when clutch is disengaged, there should be nothing turning in the transmission. Something is (the input shaft) and the synchronizer rings are creating enough friction when trying to put transmission into gear to move truck slightly. If it is still in warranty I would take it in, otherwise if it were me i would see what develops. I can't see it being the throwout bearing, maybe the hydraulics or the pilot bearing or the clutch plate dragging slightly, if the pilot bearing fails it could damage the input shaft end, if the hydraulics fail, you just won't be able to shift into gear from neutral with engine running. This could also be the case if the pilot bearing siezes up. Just my 02. bg

 

[GCroyle]

JDiehl,



If you could give TDR members a bit more, it does this when I do this, we might see some more suggestions. For example:



How far off of the floorboard with the clutch pedal when the truck starts to move? Check cold and warmed up.



Mileage?



How does the pedal feel when you push it with your hand? Often we can feel more with the fingers than the foot in a heavy winter boot. If you percieve "slop at the top" then it might be time to think hydraulics. I might be able to help you check your system over the phone.



G56 fluid, got any leaks, fluid changes to Brand XYZ?



We check for release of finished systems sometimes by turning the driveshaft by hand and easing the pedal up slowly and feeling the catch point. Engine off, wheels free to turn, etc. Observe pedal reserve travel from floorboard.



Good Luck.



To B. G. Smith,



Very good comments and suggestion, my compliments.

 

[JDiehl]

Thanks guys for all the input!



Will be driving the truck in the morning and will get a little more info.

 

[cerberusiam]

Hydrualics are cold, grease in the pilot bushing\bearing grease is cold and stiff, trans oil is cold and stiff. The input will turn even with the clutch engaged just form the rotational friction and cold shrinkage.



As long as it doesn't grind when you engage the gears and everything works good once its warm I'd say its pretty normal. When it starts happening warm then you have a problem.

 

[JDiehl]

29k on the truck. The clutch is fully depressed to the floor. Clutch feels the same to me before I noticed the rocking. When the shifter is moving into gear feels like it falls into gear. Like shifting clutchless. ATF 4 right now fluid levels good with no leaks. No grinding. Might try changing see if it helps.

 

[TBartlett1]

The cold temps should actually help prevent the transmission from turning when the clutch is pushed in due to the thick gear oil. I would check to see if the clutch fluid is low, there could be some air in it.



One other thought!

Last year I had a 06 CTD come in with the same problem and it turned out to be the clutch master cylinder was broken.

This problem happened all of a sudden, what I found was the clutch master piston which is connected the clutch pedal with linkage was pulled out of the clutch master bore and air was admitted and the clutch would not release.

The cause of this was the owner's boot getting caught underneath the clutch pedal as he was getting out of the truck. This pulled the piston out of the bore. A new slave assembly cured the problem.



One other note; I have in the past cut the line connecting the master and slave cylinders so I could replace only 1 piece. The slave assembly is a 1 piece unit but I have used compression fittings to reconnect them with no issues.



Hope this helps.

Tim

 

[cerberusiam]

When the shifter is moving into gear feels like it falls into gear. Like shifting clutchless.

That is because the input shaft is spinning from the friction cause by the cold pilot bearing\bushing. You have what is like a partial clutch engagement.

The cold temps should actually help prevent the transmission from turning when the clutch is pushed in due to the thick gear oil.

Won't prevent the input from spinning in reaction to the pilot bearing as the mass is small enough, grease stiff enough, and the oiling minimal.



When the counter shaft is engaged the stored energy of the input spinning is transfered to the power train and you get a bump enhanced by the stiff oil. The colder the grease in the pilot the more energy from the flywhell is transfered. Pretty normal in a manual trans and cold weather.

 

[TBartlett1]

The pilot bearing is very small and could not transfer that much torque unless it was in very bad condition and even then very, very unlikely.

I live in the NE with temps that go below zero. When I start my truck I keep the clutch in until the engine smoothes out a bit. When I let the clutch out the engine speed droops when the clutch is engaged due to the cold stiff oil.



When the clutch is pushed in at idle (cold) to engage 1st gear there is not enough inertia to keep the clutch plate spinning and overcome the heavy oil and cause the truck to rock.

If the clutch is operating properly it should be completely disengaged from the flywheel/pressure plate and stop almost immediately.



Something is wrong, minor, major??

Oil on the clutch could cause the same symptoms but by design oil can not get on the clutch from a leaking rear main seal.



My first task would be to check the clutch hydraulics. It does not take much air to cause issues.



Tim

 

[Little Bill]

Gotta agree with Cerberusiam on this one. ATF+4 doesn't offer much resistance at cold temps. Input shaft is spinning due to grease viscocity at the pilot bushing. Maybe not at the same RPM as flywheel, but spinning up. When trans is slipped into gear (thank you syncro rings) the counter shaft absorbs the inertia and transmits it to the axle. Bump.

 

[cerberusiam]

The pilot bearing is very small and could not transfer that much torque unless it was in very bad condition and even then very, very unlikely.



When the clutch is pushed in at idle (cold) to engage 1st gear there is not enough inertia to keep the clutch plate spinning and overcome the heavy oil and cause the truck to rock.

You would be surprised by how much rotational velocity a good cold pilot bearing will transfer. You also need to consider the fact that the clutch disk(s) do not always completely disengage and transfer a fair amount of their own on cold start. Moisture, oil, clutch dust will all create a friction that spins up the input even with the clutch disengaged.



Every manual truck I have driven in 30 years has done the exact same thing at some point. Nothing wrong with them ever, just certain circumstances occuring at the correct time. Your routine and warm up procedure may preclude you from feeling it but its pretty easy to duplicate on any manual transmission.



As I said, as it works good warm and there is no grinding of the gears when cold its a good chance there is nothing to worry about.