Well if you're able to pinpoint the sound to behind the bellhousing, I guess the next step is going to be to take it apart and see what's in there. There's not a lot of moving parts in there and I think it's gonna be tough to diagnose over the internet without looking behind

Maybe it's a stupid as something fell down there during reassembly (small screwdriver or something).

 

Ill probably start tearing into it this Saturday. I hope I see something or by replacing the pilot bearing resolves the issue. You are correct in that there isn't a lot of parts inside the bell housing. All of them are new besides the pilot bearing. Its beyond me why I just didn't replace it to begin with. It seemed to be fine when I checked it. No play and spun smooth. It actually felt like a new bearing.

 

I hate the decisions of what to do "while I'm in there ... I might as well ..." I didn't change the sleeves on the balance shafts when doing the front end seals and a month later it began leaking oil like crazy and I had to go in again. They looked great and I even put the micrometer on them and saw little wear. Fortunately, I needed to go in to retension the belts anyway.

If you didn't do it the last time the clutch bell housing was off - you may want to do the rear main seal.

 

Friendly tip: you must always weigh the cost of the "while I'm in here" against the PITA factor of doing it later.

In this case, a pilot bearing is $7.50 on Pelican (and there is a $6.50 option too).

When I dig into my car for anything that'd be considered "moderate" effort or greater, I generally put together a price list nearby of all the wear or consumable type parts I'd touch while taking it apart (gaskets, seals, small bearings, whatever). If it's a cheap part, I just order it and replace it.

The max price threshold goes up with difficulty level.

I just did my clutch 2 years and ~25k ago, but it's starting to grab pretty high up in the pedal travel. (Lots of aggressive AX starts over the last 2 years, so I imagine the disc is worn.) The pilot bearing, clutch fork bearings, guide tube... should all be fine. But I'm replacing them anyways. I'd rather drop an extra $100 in parts now than have to rip into it all later if my new clutch lasts longer. I'll probably do a fresh RMS too, even though it's not leaking.

 

A new rear main seal was installed when I rebuilt this engine 2 months ago.

 

When I did the clutch, I did the RMS, pilot bearing, clutch fork bearings, clutch fork pivot shaft, guide tube, TOB, clutch and pressure plate and had the flywheel ground. I didn't replace the fork itself, although I cleaned it up. I rebuilt the clutch slave cylinder, but didn't replace it, as it's pretty accessible.

After doing all that, I started on the front end where I had oil leaking, and I just bought a front seal kit. I should have spent more time looking at the various options that included the balance shaft sleeves in other kits.

 

The fact that I have to replace the pilot bearing is a little frustrating but, shame on me. Doing all that work to replace the pilot bearing not knowing that the bearing is 100% the issue is whats killing me. I'm trying to think of a way to prove that its the bearing and here is what I have come up with...

Remove tranny.
Start motor and wait for noise to happen.
Stop motor
Unbolt TT from clutch bellhousing.
Slide TT back just far enough so drive shaft is no longer inserted into pilot bearing.
Start motor again and see if noise is still there.

Ill prob install exhaust as well before starting again. Thoughts? Stupid? dangerous?

 

I wonder if you'd ever get the input shaft back in without disassembling the clutch and aligning it again? I've never heard a bad pilot bearing on a 951, but that wouldnt be my first guess for that sound. Any chance you put the starter ring on upside down or used nonstock pp bolts that stick out too far? Are you sure you assembled the throw out bearing in the pp properly and got the retaing circling fully seated with the retaing ring in place right side up?

 

Hey Tom.

My plan is to slide the TT back just far enough, 1/2 - 3/4 inch, so that the small end of the drive shaft is no longer inserted into the pilot bearing. I believe that I can pull the shaft out of the bearing without removing the spline portion from the clutch disc.

Starter ring is correct orientation, bolts are recessed properly and throwout bearing/rings are seated fully. I paid particular attention to the throwout bearing because I was getting some clutch chatter on previous clutch job. The chatter drove me nuts and it turned out that I didn't use enough spacer rings.

 

It seems likely you will find it when you get the bell housing open, but I understand why you want to be sure before going that far. Have you tried manually rotating the clutch disk by turning the wheels with the engine stopped, or manually rotating the engine with the clutch disengaged to see if you can hear any rubbing or bearing noise at slow speed? You'd need one person underneath. preferably with an electronic sound pickup and one person rotating engine or wheels, and another holding the clutch disengaged, but you might learn something that way.

 

Something similar to what you suggested Turbo17...

Seeing as though the car is on 4 stands I could put it in gear and bring speed up to 30-40 mph or faster if needed. If I press and hold the clutch down, turn off the engine the inertia of wheels/transmission will still keep the drive shaft spinning for a bit. The drive shaft should also be spinning the pilot bearing and maybe I can hear something then.

 

If you're sure that the noise is inside the bell housing, you're going in there regardless and this may just be wasted effort. If you're not sure, then I'd be doing what you're doing - trying to make sure I'm going into the right place. I spent a lot of time trying to figure out why my clutch wasn't disengaging. I checked the whole hydraulic clutch system, and inspected the clutch plate and wear, etc. and never did learn much until I gave up and opened up the bell housing. In my case it was just a gummed up throwout bearing. I replaced everything, including the TOB, but after cleaning it up, that bearing seems to be in great shape. I'd never use it again, but it's annoying to know it just needed to be cleaned. (I would have needed to replace the clutch in less than 5-10K anyway)

 

This is one of those things that goes through your head, you know, whats the worst possible thing that can happen and remember someone saying they broke a windshield when changing a hood strut.....anyway...

Maybe the bearing was good and you just managed to bang it with the TT install. I pulled one once and found it visibly beat up (but, in my case, still working fine).

If I really get nervous like with the throw-out bearings I take pics of those stinkin shims.
Its been awhile but IIRCC, those guide tube bolts are super short - maybe they got switched. Thats all that comes to mind...Bruce

 

I dropped the transmission, slid back TT and removed everything inside the bell housing except the flywheel and supposedly bad pilot bearing. I inspected all of the removed parts and everything checked out ok. No unusual witness marks or grease/foreign objects to indicate whats causing the noise.

After inspecting things I reinstalled just the pressure plate, bell housing and starter leaving out the clutch disc, fork, fork pivot pin, slave cylinder and TT/drive shaft. Today Ill start her up and let it get up to temperature and see if the noise comes back.

If the noise returns... then it has to be related to one of parts I did not install

If the noise doesn't return... Ill slide the TT forward, engaging the drive shaft into the pilot bearing and retest.

This is the procedure I used to install the new T/O bearing..
http://www.lindseyracing.com/LR/Parts/TECHTO.html

The only difference I did was use 2 spacer rings in step #2 in Lindsey's instructions. Ill post what I find after testing today.

 

Sounds like the best way to proceed. I'd do the same thing if it was my car. Put it back piece by piece and start it up between each piece to see if the noise comes back.