Engine/Transmission (1998.5 - 2002) Warning to others about throwout bearing noise

[WaltHess]

Just wanted to give others a heads up. My throwout bearing started to make a squeal when it was depressed, and I continued to drive it till I got my information together. Well last Sat the truck would not shift , and the clutch got real stiff. I don't have the time, nor any concrete to work on at my place, so I ran it down to a local shop to get it fixed. Didn't want to wrestle with a 350# trans, and 100# transfer case on gravel. Got a call yesterday that not only was the throwout bearing toast, it took out the pressure plate, and wore into the clutch fork as well. If I had taken care of it as soon as I heard the noise I probably wouldn't be buying a clutch now. Even with 315,000 miles on it, he said the original friction disc still has a lot of life on it. So now it is going to be $1,000 instead of $600.

 

[Ram4Sam]

I think you fixed the right way... ... As big of a job it is and the cost of removing this heavy trans and transfer case, reusing a clutch with that many miles would be a huge, huge leap of faith.

Sam

 

[WaltHess]

Even though I have 315,000+ ,,most of them are straight highway miles, very little shifting. The new clutch is in, and you would hardly know it had a clutch. Takes very little effort to release it. As I remember the stock clutch had a bit more resistance.

 

[GCroyle]

Guys,



Just a comment from a clutch guy, some of this is common knowledge, but worth repeating with this thread.



1. If the engine is turning, the clutch bearing is turning. I talked to a guy recently that overnight idled his engine, big light bulb went off when he realized the bearing was turning too.

2. Clutch bearing freeplay pretty much disappeared with the introduction of hydraulic release systems. Pass car and light truck as primary reference.

3. Extend clutch bearing life by NEVER resting your foot on the pedal.

4. Use the clutch for shifting, minimize the amount of high bearing load time by selecting N at lights or other situations and take your foot off of the pedal.



Installation comments.



Lately I've seen way too many cases where the bearing was installed w/o greasing the grease groove in the collar. these were not our parts, it's a long story and I'm not elaborating but I've seen total failure in as short as several months. This causes hard pedal, bearing cannot always relax and slide back freely. This can hold pressure on the diaphragm spring reducing the clampload. The Dodge fork is robust, does a good job. A film of grease where the fork pushes on the ears and a bit on the sides of the ears where the fork rubs. Fork installation, part number is in lower left as viewed looking at input shaft.



The bearing may appear off center to the collar, normal. This is the self aligning function, snap it L, R, Up, Down. Just install it, the bearing will self center after startup and a few release strokes.



What I'd expect from a high mileage teardown, the bearing is dry, free spins, howls a bit and it was just hanging in there out of sheer guts.



The biggest reason for a high mileage preventitive teardown, the pilot bearing. If the engine is running and the pedal is down, clock is running on any pilot bearing. Extend life by selecting N when possible when stopped and take foot off of pedal.



One more, replacing a clutch with basically the same type clutch will almost always result in a softer pedal, normal. As the disc gets thinner from wear, release load increases. New system release load is back to original PLUS the bearing is sliding freely, not dry and nasty feeling.

 

[BigPapa]

1. If the engine is turning, the clutch bearing is turning.

Hello Gary,


Please explain this. What bearing are you saying is turning?

Thanks.

 

[NIsaacs]

The throwout bearing. With hydraulic release systems the bearing is always in contact with the clutch fingers so if the engine is running the bearing is too.

Nick

 

[Gary - K7GLD]

The throwout bearing. With hydraulic release systems the bearing is always in contact with the clutch fingers so if the engine is running the bearing is too.



Nick

BUT presumably - and hopefully - with very little or no load?



You'd think a spring loaded pull-back setup would exist, that would unload the throwout bearing...



But then, manufacturers are always counting pennies -and main concern is getting the unit somewhere past the warranty period...

 

[cerberusiam]

BUT presumably - and hopefully - with very little or no load?

Exactly. When the clutch is out, yes. When the clutch is engaged, no.

That is why Gcroyle mentioned N and foo toff the clutch at stop lights. The high load sitting and waiting is hard on the throwout bearing.

 

[NIsaacs]

This clutch was my original and working fine, I just brought a load of hay out of Utah. However, after talking to GCroyle about some hard peddle issues, I decided to pull it, 212k miles, it was toast. Notice the clutch fingers, the throwout bearing was ready to push right threw them, they were paper thin. Both bearings were dry but still rotating ok, the disk was almost touching the rivets. Hot spots on both the flywheel and clutch cover.



Nick

 

[Gary - K7GLD]

This clutch was my original and working fine, I just brought a load of hay out of Utah. However, after talking to GCroyle about some hard peddle issues, I decided to pull it, 212k miles, it was toast. Notice the clutch fingers, the throwout bearing was ready to push right threw them, they were paper thin. Both bearings were dry but still rotating ok, the disk was almost touching the rivets. Hot spots on both the flywheel and clutch cover.

Nick

Nick, I'd hafta say, you got your $$$ worth outta that clutch setup!

NOW, when changing out all that stuff, including the throwout bearing, do you usually also change the pilot shaft flywheel bearing?

I did mine, and getting the old bearing out was nearly as hard as changing out the rest of the clutch!

 

[NIsaacs]

Nick, I'd hafta say, you got your $$$ worth outta that clutch setup!



NOW, when changing out all that stuff, including the throwout bearing, do you usually also change the pilot shaft flywheel bearing?



I did mine, and getting the old bearing out was nearly as hard as changing out the rest of the clutch!

Gary, the pilot bearing is easy to remove with the flywheel off, just find a socket that size and whack it out. This was on my '01. I also did my rear main seal. At about 280k on my '91 I pulled the transmission and checked the clutch, it was fine so I just changed the throwout bearing, the pilot bushing (brass) was fine so I left it. I have 319k on it now but it is 4x2 with the little Getrag so it is a lot easier to work with. Anytime you do a clutch, always inspect the input shaft splines for any wear and also the throwout bearing slider tube.



Nick

 

[BigPapa]

The throwout bearing. With hydraulic release systems the bearing is always in contact with the clutch fingers so if the engine is running the bearing is too.

Nick

I'll have to disagree with this. If the throw out bearing was turning anytime the engine is, the bearing would not last 50K miles, probably not even 25K. It has no lube except the grease you put in it. Just like the pilot bearing.

Saying this is due to the hydraulics would be saying that your brakes are always dragging because they're hydraulic.

 

[NIsaacs]

Scott,



What Gary and I posted is a true story. When you release the clutch peddle the only thing that pushes the throwout bearing back is the pressure plate fingers, that is where it stops. There is nothing to pull it away from the fingers like on a manual clutch linkage with a return spring. Disk brakes work the same way, they always lightly touch the rotors. Drum brakes have a return spring so they will run clear if the adjustment is right.



Nick

 

[GCroyle]

I'll have to disagree with this. If the throw out bearing was turning anytime the engine is, the bearing would not last 50K miles, probably not even 25K. It has no lube except the grease you put in it. Just like the pilot bearing.

BIGPAPA,



Can you post a picture of the clutch bearing and fork return spring or system that creates the freeplay?



A bit more detail.



The slave cylinder has a spring in behind the piston body pushing from the housing or casting. It pushes the fork forward and applies a preload to the bearing. The bearing turns continously. The hydraulic system is at ZERO PSI with your foot off of the pedal. When you push on the pedal, the master cylinder closes a valve (incoming fluid supply) and creates pressure, the slave cylinder pushes forward and we get release travel.



To demonstrate on you own, next time someone has a trans out (with bellhousing if NV4500) install the bearing and fork then install only the slave cylinder from an old system, no fluid, no line, no master, just the slv cyl bolted up.



Now, try to push the bearing back in to its mid point of the travel range, feel the resistance, thats the proload.



Or with the clutch and trans installed, take a used slv cyl (retaining straps already snapped) and try to install it. You have to push it into position and hold it while you bolt it up. Why, its not the fluid, that peacefully just changed location and went to the reservoir. You're compressing the spring inside the slv cyl.



Simpler demonstration, find an internal slave cylinder from a Ranger or 96- Chevy C/K series. Make sure it doesn't have any fluid in it and leave the bleed screw open. Now compress the bearing back against the housing, feel the spring? There is a spring behind the bearing that applies a constant preload to the system.



Bearing design used to REQUIRE freeplay. Freeplay was an actual air gap between the bearing face and the levers or later fingers that allowed the bearing to NOT TURN with your foot off ot the pedal. The bearing of choice was a thrust bearing or aka step shell by some folks. Great for a direct inline with the input shaft load, but at high RPM the ball bearing actually want to fling out and cause wear internally. The current bearing design of choice is called angular contact. The load thru the ball is at about a 45 deg angle, so it does just fine with thrust or radial loads. Combine angular contact with self aligning and actuate with a hydraulic system and that is todays clutch release system.



Why the long answer? Not to disprove BIGPAPA's statement, but just an attempt to offer the inner workings of the system to help other diagnoise the problem. We (the clutch industry) have seen a lot of clutches blamed when the problem was elsewhere and the next clutch installation they either got lucky or learned from the previous failed installation.



I take a bunch of tech calls, my US record for most NV5600 R&R clutch fix attempts on one truck trying to get it to release... ... ... ... drum roll please... ... ... .



14 R&R's back to back, one tech, one truck, untold lets try THIS BRILLIANT idea!!!!!!!! next. Then contact the supplier, he's our best account, we gotta , oh never mind.

 

[BigPapa]

My throwout bearing started to make a squeal when it was depressed

So why this? Why not a constant squeal from the bearing if it's constantly turning?

 

[NIsaacs]

So why this? Why not a constant squeal from the bearing if it's constantly turning?

Not enough stress/pressure on the bearing when it is at rest. With the added pressure of depressing the clutch, the rollers or ball bearings will protest with a squeal.



Nick

 

[GCroyle]

My throwout bearing started to make a squeal when it was depressed



So why this? Why not a constant squeal from the bearing if it's constantly turning?

Healthy clutch release bearings do not squeal. Worn, end of service life release bearings can squeal and can completely come apart if ignored long enough. The seals go out, clutch and cast iron dust permeate the races, RPM, load, end of service life.



Comments based only on diaphragm clutches.



This is one of the great challanges in diagnosing clutch related noises. We really need to know more details, any history, mileage etc. But heres the big one, pedal position relative to the noise.



Pedal up, foot off the pedal: Release bearing is turning with the bearing preload force only, pilot is completely inactive, running at same speed on both outer and inner race or needles.



Pedal 1/4 of the way to the floor: Release load on bearing has increased dramaticly, but may not have peaked. Pilot bearing still sleeping.



Pedal 1/2 way to the floor: I'm expecting at this point that you have hit (roughly) the peak pedal effort of the diaphragm clutch. Maximum release load. Pilot still sleeping.



Pedal 3/4 and more to the floor: Release load has started to drop off, and as the disc spins down the pilot bearing starts doing its job.



So with the above position vs. noise info, where was the pedal relative to the noise and can you do anything with the pedal only that controls or triggers the noise? Also vehicle and clutch history is very helpful.

 

[GCroyle]

Guys,



This is an R&R we did on KLauber's truck http://www.youtube.com/watch?v=AihVShe0Ta0&list=UUSufPrfq8lm0rYJ0cM03jXg&index=4 look at the 5:12 minute mark. We're spining the bearing with a finger tip, hear that noise, easy. But Ken didn't report that noise or the noise from the broken DMF internal rivets, his issue slipping.

 

[BigPapa]

Alrighty then. I stand corrected.

Those throw out bearings are a lot tougher than I've given them credit for.

Thanks.

 

[GCroyle]

Alrighty then. I stand corrected.



Those throw out bearings are a lot tougher than I've given them credit for.



Thanks.

BIGPAPA,



Maybe someone with a little time on their hands will take a minute or two and calculate how many revolutions a clutch bearing might make in a 100,000 mile service life? You'd need to assume an average MPH figure out the hours to acheive the 100,000 mile mark, RPM, RPM/HR and so on. And FORD (easy Harvey) uses plastic collared bearings on 7. 3L's thru last handshakers for diesels they built.



I think we might have been in the same place several years ago with the Mid-TN gang either at Underwood Tire or Beans for some good fun.



Gary