Improper Pilot Bushing Installation

[jss06c6]

Here's a textbook example of improper pilot bushing installation and the damage it causes. The oilite bronze bushing was not set to correct depth and was contaminated with grease. Not only was the pilot bushing shot, the input shaft tip is destroyed. Significant vibration upon acceleration from 1500 rpm felt in shifter as well as the floor. Flywheel (Ram Aluminum) was also damaged (now resurfaced and balanced) along with the throwout bearing (rebuilt).

The input shaft was continuously riding on the face of the pilot bushing!8643864486458646

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[Ccmano]

Improper bushing seating depth and use of grease when none should have been applied....
H
:cheers:

[jss06c6]

Properly set with FW machined and balanced..[ATTACH][ATTACH][ATTACH][ATTACH]

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[Paul Workman]

Improper bushing seating depth and use of grease when none should have been applied....
H
:cheers:

Seating depth, I can understand. But, greasing the broze bushing (pilot bearing) resulting in THAT particular failure - considering those bearings are impregnated with lube (are they not?) out of the box?

I'm seeing the damaged(?) input shaft and bearing, and not intending to be casting dispersions, but I am a shade skeptical of the diagnosis. I know I'm setting the stage for ridicule, but I'd want to know more...:happy1:

[Dynomite]

Seating depth, I can understand. But, greasing the broze bushing (pilot bearing) resulting in THAT particular failure - considering those bearings are impregnated with lube (are they not?) out of the box?

I'm seeing the damaged(?) input shaft and bearing, and not intending to be casting dispersions, but I am a shade skeptical of the diagnosis. I know I'm setting the stage for ridicule, but I'd want to know more...:happy1:

I concur...…..Those impregnated bushings (I use needle bearing bushings on ALL Zs) do not need grease. Matter of FACT...…From a different Pilot Bushing Failure analyzed by ZF.Doc…...

From the ZF.Doc

I replayed the video about twenty times. It sounds like the pilot bushing is
compromised. Install GM fluted pilot bushing (GM P/N 10125896). WARNING: Applying grease in an oil-lite type pilot bushing will cause the pilot bushing to fail within the first one percent of its normal life expectancy. Although very dry looking straight out of the bag, the oil-lite type pilot bushing is infused with enough oil to lubricated the input shaft pilot tip for the entire service life of the clutch. Why not just install a pilot roller bearing instead? When a pilot roller bearing fails, the input shaft pilot tip will be compromised requiring removal of the input shaft for pilot tip repair or replacement of the input shaft.


I seems to me that rather simple measurements would prove exactly how far the transmission nose penetrated the bearing. Maybe the Transmission was loose from the Bell Housing :p

It appears that the marks on the Trans tip would indicate the Trans was seated well into the Pilot Bearing :dontknow:

All sorts of possibilities :rolleyes:

Ridicule ???? ……….You mean Debate on this Forum :D

What we have to do is load our photos into our Forum Albums (Registry or CF) so we can see what is going on :thumbsup:

http://www.zr1.net/forum/picture.php?albumid=387&pictureid=3856

[Paul Workman]

As I study the photo of the input shaft to the extent the photo allows, there was GALLING occurring in 3 distinct bands along the shaft. Why not along the entire contact length between the bearing and the input shaft??

You don't get galling between steel and bronze. There has to be a third element (steel) contaminant in the mix. And, when you look carefully, is that a bit of the grease on the end of the input shaft? Note that it no longer looks to be viscus, and it appears to be impregnated with metal filings.

I'm intrigued...

Tell ya what: Not being able to inspect the clutch components directly, a real forensic analysis is difficult. That said, and this is just a SWAG mind you, but something else was going on with that installation - i.e., the REAL reason CONTRIBUTING to the demise.

Again, I'm only seeing the pictures. I could be wrong, but there appears to be waaay too much metal filings contaminating that bearing, evident in the "grease" residue. So, I'll toss this in for your consideration, this possible hypothesis:

The grease became saturated with the normal clutch disc (dust) material, true. But, far more important is the metal filings. The combination of the two combined with the grease to form a stiff material, forming a barrier scattered randomly along the input shaft. The metal filings became dammed up and HEAT soon followed.

The bronze bushing then became impregnated with the metal filings that were clumping up along the shaft. That led to isolating the lubricity of the bronze from the shaft, and RED HOT HEAT (also very evident) ensued to the point of initiating the (steel on steel) galling evident from the pictures.

Replacing all the damaged parts sets up a "do over". And, if in fact there IS evidence of metal filings, the cause of that evidence may too have been eliminated. But, I'd really want to run that filing contamination to ground - assuming there ARE significant amounts of such contamination remaining to be found. Unless the cause of the metal filings is identified and corrected, the stage is set for a sequel of the first act.

That's my hypothesis - and worth the price of free internet advice, no doubt. I just don't buy the theory that the grease, because it was used, caused the galling. It may have been a contributing factor, but were there no metal filings, would the galling have taken place anyway?? I doubt it.

[Paul Workman]

I concur...…..Those impregnated bushings (I use needle bearing bushings on ALL Zs) do not need grease but on the other hand I am not so sure adding grease would cause such a failure.


I seems to me that rather simple measurements would prove exactly how far the transmission nose penetrated the bearing. Maybe the Transmission was loose from the Bell Housing :p

It appears that the marks on the Trans tip would indicate the Trans was seated well into the Pilot Bearing :dontknow:

All sorts of possibilities :rolleyes:

Ridicule ???? ……….You mean Debate on this Forum :D

What we have to do is load our photos into our Forum Albums (Registry or CF) so we can see what is going on :thumbsup:

Ya beat me to the "enter" key, my friend!!;)

[WARP TEN]

An interesting situation and discussion. I tend to agree with Paul that it would seem there must be a source of steel or other strong abrasive to cause all that galling. The shaft is (I believe) case hardened steel and the bushing is bronze, a much softer metal so I would expect that it would not in itself cause the galling, rather the scoring would likely be more pronounced on the bushing itself. Curious to know if you examined the grease for what appear to be metal filings in it (although presumably some of it probably came from the shaft) and whether there was scoring inside the bronze bushing. --Bob

[Dynomite]

Here's a textbook example of improper pilot bushing installation and the damage it causes. The oilite bronze bushing was not set to correct depth and was contaminated with grease.

The input shaft was continuously riding on the face of the pilot bushing!



The marks on the Trans Shaft do not indicate that (Red Highlight Above) but possibly later after considerable use the Pilot Bushing drifted to a greater depth and the Trans Shaft finally was free of the Pilot Bushing.

http://www.zr1.net/forum/picture.php?albumid=387&pictureid=3856

ZF.doc analyzed a different Pilot Bushing Failure somewhat similar to this Failure in this Thread......and suggests Applying grease in an oil-lite type pilot bushing will cause the pilot bushing to fail within the first one percent of its normal life expectancy.

This was posted by Daryll regarding the
similar Pilot Bearing Failure (not this failure in this thread)...…..
From the ZF.Doc………….
I replayed the video about twenty times. It sounds like the pilot bushing is
compromised. Install GM fluted pilot bushing (GM P/N 10125896). WARNING: Applying grease in an oil-lite type pilot bushing will cause the pilot bushing to fail within the first one percent of its normal life expectancy. Although very dry looking straight out of the bag, the oil-lite type pilot bushing is infused with enough oil to lubricated the input shaft pilot tip for the entire service life of the clutch. Why not just install a pilot roller bearing instead? When a pilot roller bearing fails, the input shaft pilot tip will be compromised requiring removal of the input shaft for pilot tip repair or replacement of the input shaft.

Marc Haibeck specific diagnosis on a similar Pilot Bushing Failure to the one in this thread explains...……

"It is a faulty pilot bushing for sure. What causes a pilot bushing to fail? Grease applied to the inside diameter surface of an oil-lite (oil saturated) pilot bushing is the number one cause for pilot bushing failure. Grease applied in a pilot bushing eventually dries up and clogs the otherwise normally self-oiling pours of the bushing".

See...…………….
Throwout Bearing and Pilot Bearing TIPS (http://www.zr1.net/forum/showthread.php?p=239369)
Pilot Bearing Failure TIPS (http://www.zr1.net/forum/showthread.php?p=261075)


Paul...…..Please delete my initial suggestion made without checking the -Solutions- thread first which is an incorrect suggestion I was Not so sure about :p:p ………."but on the other hand I am not so sure adding grease would cause such a failure".


Again......I use Roller Bearing Pilot Bushings which take a good amount of grease during the installation even though ZFdoc suggests...…."Why not just install a pilot roller bearing instead? When a pilot roller bearing fails, the input shaft pilot tip will be compromised requiring removal of the input shaft for pilot tip repair or replacement of the input shaft". ( I figure the Trans Tip was compromised in the this case with a much quicker failure than one would expect with a roller bearing) :thumbsup:

[Paul Workman]

Interesting topic, 'fer sher'.

That said, and having serviced many a clutch, starting with my part-time job as a mechanic, back in my college dayz, I became slightly paranoid about riding the clutch; either at a stop light or waiting for an opening in bizzy city traffic.

[jss06c6]

Bill Boudreau and I discussed before and after tear down. Grease contaminated the oilite bronze bushing (not a bearing), destroyed the lubricating properties of the oilite bronze. Input shaft tip galled as a result. Bushing was set shallow. When the trans was bolted up, the input shaft face was pressed against the bushing face, causing more heating from friction caused by loss of lubricating properties of the oilite bronze. Add to this a flywheel that was not planar causing erratic engagement with the clutch and pressure plate and you've got a recipe for disaster.

Clutch, flywheel and pilot bushing were NOT installed correctly.

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[Top Toy]

It appears from the photos that the failed bushing was a plain bore as opposed to the fluted style generally recommended today. The flutes provide a place for any contaminants to accumulate without compromising the already tight clearance between the OD of the pilot shaft and the ID of the bushing. If, in this case, the shoulder of the pilot shaft was riding hard on the face of the bushing, that would have caused the tip of the shaft to heat up when it was stationary and the flywheel was spinning (clutch depressed in gear) and expand to the point where there was an interference fit between the shaft and bushing. Having grease in that tight gap would only have made matters worse since it had no place to go and likely started coking in the heat. The metal particles in the mix probably came from the shaft itself as it heated up and flaked off.

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[jss06c6]

It appears from the photos that the failed bushing was a plain bore as opposed to the fluted style generally recommended today. The flutes provide a place for any contaminants to accumulate without compromising the already tight clearance between the OD of the pilot shaft and the ID of the bushing. If, in this case, the shoulder of the pilot shaft was riding hard on the face of the bushing, that would have caused the tip of the shaft to heat up when it was stationary and the flywheel was spinning (clutch depressed in gear) and expand to the point where there was an interference fit between the shaft and bushing. Having grease in that tight gap would only have made matters worse since it had no place to go and likely started coking in the heat. The metal particles in the mix probably came from the shaft itself as it heated up and flaked off.

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[WARP TEN]

Interesting topic, 'fer sher'.

That said, and having serviced many a clutch, starting with my part-time job as a mechanic, back in my college dayz, I became slightly paranoid about riding the clutch; either at a stop light or waiting for an opening in bizzy city traffic.

Agree--I long long ago developed the habit of always putting the car in neutral and getting off the clutch when at a stop. Always did it. Never had a clutch or bushing failure even when the clutch had been in for 75,000 miles or more.--Bob