Not that I know anything about transmissions but after reading the thread my bet is the bushing is allowing the input shaft to turn even with the clutch pushed in. Keep us posted interesting read!!

My new mechanic gave me a fresh perspective on why the pilot bushings are going out every 1500 miles. And he may be right.

The slave cylinder push rod is not perfectly perpendicular to the clutch fork. The rod is pushing up at an angle of about 35 degrees. He theorizes that the upward pressure on the shift fork is causing the fork to press on the input shaft causing the shaft to press on the pilot bushing thus causing premature wear.

We are going to fab a new slave bracket so that the piston and rod travel at a right angle to the clutch fork thus eliminating any abnormal force on the other parts.

Then, another bushing will go in and we will see what happens after that.

Makes sense to me now!

I think mine has a "dragging" or something when I go from 1-2. I don't hear any grinding at all, but when shifting like there is some resistance. I don't feel this going from 3-4. I will also add that I notice it more when I'm accelerating rapidly (like getting into a short acceleration lane) than in just normal usage.

Plain and simple, the disc and thus the input shaft is continuing to spin while the pedal is depressed. Complete release of the disc is measuresd in "Thousandths" of an inch within the bellhousing. The pressure plate with a hydraulic slave is self adjusting and if proper travel (release stroke) is not originally designed into the application it will never be able to be obtained by any amount of adjustment. No two set of disimilar components (clutch disc/pressure plate) will require the same travel for complete release. Thats why there is in reality a range necessary to work properly. In the case of Hydraulics it's a matter of juggleing the diameters of the slave and Master without creating over travel at the throwout bearing interface. Once obtained it's a happy moment.

I am not so sure on the physics of the clutch arm pushing on the throw out bearing and in turn deflecting the input shaft causing binding of the pilot bushing is accurate. In fact if you take off your slave cylinder you will find the clutch arm to pilot bearing has quite a bit of movement by design. It is impossilbe to deflect the input shaft by use of the clutch arm so slave cylinder misalignment may result in reduced slave cylinder life it will have not affect on input shaft to pilot bearing / bushing.

Tell him to guess again. I would take a radial runout measurement on your input shaft, id measurement on your bushing/bearing. Obviosuly radial runout should be zero.

That is true.

The throwout fork and bearing come nowhere near the input shaft.

Every manual trans has a snout for the throwout bearing to travel on. The input shaft runs inside the snout.

If there was any contact is this regard you have a clutch that wouldn't disengage at all, and a high pitch squealing noise.

What Gaz64 say's

The T/O bearing runs on the snout of the bearing retainer. NOT the input shaft.

Run from the new guy & find a new, new guy that will investigate, NOT guess!
This is getting expensive & a waste of time for you.

JMO
Craig

Went to the shop yesterday morning and examined the pieces.

Clutch is fine, throwout bearing is not.

The clutch fork (maybe due to the misaligned slave push rod) was off the fulcrum and applying a side load as well to the throwout bearing, possibly resulting in only partial release of the disc.

So, the pilot bushing may not have been the culprit after all. Might have been a series of events leading to a slightly dragging clutch disc. Every time we replaced the pilot bushing, we replaced the t/o bearing too just for safety sake.

Putting it back together today with a new slave bracket so the rod is pushing straight. New pilot bearing and a new t/o bearing.

Will test and report in a few days.

Once you get the mechanical fork aligned properly, then adjust "clutch engage" distance (pedal engagement from top) and add an ADDITIONAL 1/2 to 3/4 inch travel. This will account for heat buildup. This is a naturally occuring situation. Although it may feel a little strange, Do not adjust this clutch linkage like your mid-sixties corvettes. Old timer (read:experienced) at Millville taught me this valuable lesson. We also run Mobil 1 in both trans and rear.

Mechanic fabricated a new slave cylinder bracket so the slave push rod is pushing perpendicular to the clutch fork. Replaced t/o bearing and pilot bearing.

50 miles on the new setup and, so far, trans shifts like it new. Will report back in about 1500 miles. That seems to be the point when everything turns to s--t!

Make sure the TO bearing is not installed backwards !!!


.

The TKO input shaft will only turn inside the pilot bearing when the clutch is disengaged, so wear here only happens when you are pressing the clutch.
The rest of the time the TKO input shaft is turning with the flywheel and the input shaft in not rotating inside the pilot bearing and thus not wearing.
If the pilot bearing wears off so fast (in most cars they last a lifetime) it might be that the clutch is slipping and the pilot bearing is doing an abnormal work supporting the rotating input shaft.

So it now appears the culprit all along was the relationship of the slave cylinder pushrod.

All clutch mechanisms push or pull on the throwout fork parallel to the input shaft.
If the push or pull occurs at an angle, it no doubt tries to twist the fork and apply uneven load to the throwout bearing.
If the bearing carrier has a little more than acceptable clearance on the bearing snout, it will not be parallel or concentric with the pressure plate fingers.
Uneven release results in a dragging clutch and difficult shifting, especially from rest.

I haven't visited this thread in a while but I feel the pain you guys are going through. Consider this for a moment:

Whie it is possible that one or even two of you may have had a faulty throwout bushing/bearing installation, it is highly improbable that all of you or your installers can not master the installation of a throwout bearing.

The drag of an improperly installed or worse failed throwout bearing or an improperly adjusted clutch can overwhelm the synchronizers and produce the problem you are experiencing. The problem can also be produced by synchronizers that are barely up to the job of synchronizing the gear sets.

The problem is the latter not the former. The synchros in the TKOs are brass rings like we used to see on T-10s, Toploaders, and A-833 Chrysler 4 speeds. With the new lubricants, and metal finishing on the the synchronizer gear cones the plain old brass rings can't do the job anymore.

If you look at a T-56 they went from paper assisted dual friction surfaces to triple cone versions of the synchro to get improved shift quality. Tremec knows the problem there just hasn't been any fix available or desire to provide a fix - until now.

If you go to Liberty Gears they have an improved synchronizer available with a carbon fiber friction surface. They also have a retrofit to correct the 2-3 shifting problem. The synchros were about $50 each when I last checked and the shift fix was comparably cheap. Give it a try you'll like it.

Ed

It's only reverse that drags, the synchro's are masking the problem in the other gears. Where it is most likely the input shaft drag is so slight "at speed" it really isn't a factor anyway. When stopped, however, that slight drag is what is causing the non-synchro reverse gear selection to be problematic.

Madmax says,
THAT sum's up the problem in my opinion. After so many adjustments of the clutch components by different shops it is clear that is not the problem. Which only leaves one variable, the input shaft bushing dragging on the input shaft, keeping it in rotation.

Changing over to a bearing, from a bushing, is a good approach in this case and it appears that has now been done.

150 miles and all is still good.

Just a TKO related FYI:

I had a brand new, less than 100 miles, TKO 600 that was problematic with reverse, had to select 5th at the very least almost every time.
On the grid at VIR the car in front of me could not get started, so I grabbed for reverse and SNAP! Broke the linkage like a dry twig.
Done for the weekend.........
What we found under inspection was the 5-rev linkage, (looks like a connecting rod) is made out of junk white metal. This may not normally be an issue but the neutral allignment was off, causing a engagement issue.
Sent the trans back, they sent me a new trans which I had blueprinted to exacting specifications, my Tremec guy said this trans was assembled in Mexico and many just like it are "sloppy" mine was no different.
Oh BTW he first had to sent back a cracked housing (at the input shaft) probably happened during shipping, after that he did his magic........so far so good.
If I ever have another problem with this thing, in goes a Kees alumin case WR toploader, end of story.

Sorry to hear of your hellish problem. As we all seem to agree that a spinning input shaft would cause this grinding. And now you've aligned everything you should be good to go. I read that clutch plate gap should be a minimum of 0.100" for the TKO to make absolute no possibile clutch plate spin. So if this is your final setup and you get gear crunch then you still have rotation of your input shaft with clutch disengaged. So what else can cause the shaft to spin? This is a shot tn the dark. But what about crankshaft end play? Say you measured every thing and you have 0.005" between the bearing and the spline and you have 0.010" of crank end play. With a situation like this a few thousands of movement of the crank and some expansion of components due to heat you end up with the shaft being driven by a great deal of friction. Not enough to move the car or the wheels, but enough to keep the shaft in rotation?. Arthur

In my example, this never became an issue until the trans warmed up.

Ok, here we are at the 1000 mile mark.

Trans shifts smoothly into reverse when cold but is starting to catch a few teeth when hot. And yes, I always shift into a forward gear or two before engaging reverse.

First gear will OCCASIONALLY, resist going into first gear when hot. Hasn't done that for 1000 miles.

Clutch feels good, but I'm going to adjust a mm or two and see if conditions improve.

Hope this isn't the beginning of the next chapter of clutch problems!