Thrust bearing noise..... or is it?

[SADLOTUS]

Hi all,
Just had the engine out for a bit of a refresh and at the same time I had a close ratio gearbox built (woohoo! looking forward to that!). Put in a new clutch and pressure plate, new thrust bearing and new thrust bearing carrier springs - everything else was as it came out.
Got the engine back in, fitted a remote clutch bleeder (to make life easier) and adjusted the clutch to what I thought was right.
Baring in mind the car is up on sturdy axle stands, steady and safe I started the engine.
Let it tick over and checked for leaks and smoke.
Ticking over up in the air, even in neutral everything sounds louder.... I could hear a low graunching noise.
Risked sitting in the car and selecting first (checked wheels could turn etc - despite doing what is quite dangerous I'm very cautious and double checky).
With the clutch disengaged (foot off) there was a graunching low roaring noise, foot down and clutch engaged the sound goes. All my motoring life that has indicated a worn thrust bearing. But it's new! In any gear and neutral the noise was there.
Dropped the car to the ground and 'drove' a very few yards in the barn back and forth.

Reading through various forums the opinions are split between the noise for a noisy thrust/release bearing being there when the clutch is engaged or when it's disengaged. The alternative suggestion is the main or layshaft in the gearbox... ! But it's new!

Right.... I don't want it to be either because it's an engine out either way.
But... The clutch bites right at the bottom. I'm hoping the bearing might be very slightly dragging, and spinning.

I didn't have time to adjust the slave rod because it was teatime, and to adjust the clutch meant jacking up the car once again. Also, the slave cylinder adjusting rod has about four threads left on the adjustment.
Suddenly, I'm confused as whether the rod needs to be adjusted shorter or longer.
If I make it shorter will the clutch bite higher up and vice versa?

Opinions please.

doh. I've left the manual in the car.
I've added a picture of the car in the barn coz I like it.
It's taken 51 years to progress to this point... and it's still not my barn.

[nmauduit]

I see it this way : if you adjust the rod longer, the whole hydraulic/mechanical chain between the foot and the clutch gets longer, so for a given clutch position it corresponds to a higher pedal.

[Panda]

Hi Sadlotus, if you have assembled the throwout (thrust) bearing properly and with the correct, or any, clearance at the adjuster, the bearing is NOT turning when your foot is off the pedal. Hence it cannot make any noise. However the input shaft/gear and the layshaft gear are turning and may be noisy. The input shaft bearing in the back of the crankshaft only turns when the clutch is depressed, but that is not when your noise is occurring, so isn't the problem. Re the adjuster length. Shortening the rod increases the free play and therefore you have to depress the pedal further for it to release, so it will engage closer to the floor when you lift your foot. I do think from the "graunching"sound that you describe, it will be an internal gearbox fault.
Good luck!
Alan P.

[Panda]

Hi again SADLOTUS
I just had a further thought. You mention that you have just fitted a close ratio gearbox. It's not a straight cut gear train by any chance? If that's the case, it's normal to be very noisy and not really suitable for a road car unless you are quite deaf!!
cheers
Alan P.

[UAB807F]

Hi all,
With the clutch disengaged (foot off) there was a graunching low roaring noise, foot down and clutch engaged the sound goes. All my motoring life that has indicated a worn thrust bearing. But it's new! In any gear and neutral the noise was there.

Those symptoms describe my car when the input shaft bearing broke up although in my case it wasn't a graunching sound more of a grumble. This stopped as I pressed on the clutch pedal because then you're disengaging the gearbox. Release the clutch pedal and the input shaft will turn so any noise is gearbox related ?

As already posted it might be normal for your gearbox, I only have experience of the standard box and considering the metal filings that came out afterwards it certainly wasn't normal then !

Brian

[rgh0]

A few issues here i think

1. With the car on the stands and the gears engaged and transmission running you get a loud noise that goes away when you push the clutch in. ---- In my experience this is normal and may not indicate any issue. The body set on rigid stands transmits all the vibrations differently. Plus the suspension at full droop generates a lot of vibration in the rear end. All this adds up to a lot of unusual noise.

If the noise goes away when you leave it in neutral with the engine running it says all things up to the input shaft and lay shaft and spinning unselected gears is OK.

I would drive the car and see what it sounds and feel like on the road

2. The clutch engages and disengages near the floor.---- you need to check the free play on the slave cylinder push rod and adjust it to the factory spec in the manual. if it still engages to low try adjusting the rod to reduce free play to less than the spec but still leaving a very small amount of free play. if it still is near the floor then you need to bleed the system again. Sometimes also new clutches will engage / disengage nearer the floor until they bed in and polish the friction surface. So I would bleed and adjust until it is drive-able and then drive it for a while and bleed and adjust again to see if you can get to the right engagement location. If still a problem I would then rebuild the master cylinder and slave cylinder and bleed and adjust again.

I would not pull the engine again until I had exhausted all the options

cheers
Rohan

[SADLOTUS]

Hi all,
The gearbox is a helical gear close ratio from new parts - except the casing.
I agree with you Rohan, I'll adjust the slave and drive for a day or two to see if it settles.
Rebuilt the slave this year, Master rebuilt last year.

I can't get to the car til later today after work.
I have to take the exhaust off to adjust the slave rod.
I will let you know how it goes.

Many thanks for the input, I still love this site and learn every time, even after all these years

Paul

[webbslinger]

You have sort of described the bad noises that came from my car when I thoughtlessly applied grease to a greasless pilot bearing.

[el-saturn]

....... i am just wondering WHY the exhaust has to be taken off? is a +2 or 130 different - my 36 4982 needs no such removals! sandy, alps

[SADLOTUS]

Evening all,
went down to the car with all good intentions but within a few minutes it all came to a halt when the trolley jack gave up the ghost.
Managed to bleed the clutch again but no air.
Will try again asap with a new jack.

Webslinger - I may have inadvertently/on purpose greased the input shaft into the pilot bearing. What was the outcome with yours?
El-Saturn - I'll post a pic soon to show how close and tight it is under there. I have a 4 branch manifold - a Geoff Howe from many years ago. Anyway, when I can jack the car up, it's only a 10 minute job to get it off (not the manifold tho HA!)

ttfn
Paul

[webbslinger]

Hey Paul, well, I had to pull tbe motor, again. It sounded just as you described, not at all what you'd think a little shot of grease would produce and I went through all the gyrations you are. If you did grease it I'll bet that is the problem. If it's any consolation to you, I've had my engine out 5 times before - I think- getting it all right. The pilot was #4. You just need to get in the right frame of mind; how many people get to pull and work on a twin cam? I found that a little mini gear puller specifically for pilot bearings from a rental place worked best for getting the old one out. Thogh lesson: greasless = NO grease!

[Craven]

The input shaft pilot bearing has an internal lip seal at one end! reason?
Ron.

[denicholls2]

Another consideration is that you scenario is leaving the driveline unloaded except for friction of the parts, (which shouldn't be substantial). This is nothing like using the car, where there's almost always a uniform force of acceleration or deceleration. This scenario (exacerbated by rotoflexes loading and unloading the assembly by virtue of a large droop angle) can cause the gears in both the transmission and the differential to 'use their play' and rattle/whine. Normally these surfaces are in full and loaded contact with each other.

I'd definitely drive it before reaching any conclusions.

[webbslinger]

Paul,
I just wanted to tell you that I had serious doubts that a new pilot bearing alone could make that much noise. It sounded horrible. I thought there was a better than even chance that the noise would still be there after all the work replacing it, but it was the bearing.

[rgh0]

putting some grease in the pilot bearing would only be a problem if you over fill it and got hydraulic lock when you pushed the shaft into the bearing.

This is actually an easy way to remove the pilot bearing if you dont have a suitable inside puller - -- fill it with grease and the hammer a bolt of a close fit diameter into the bearing and the grease hydraulic pressure pushes the bearing out.

cheers
Rohan