Engine/Transmission (1994 - 1998) Pilot Bearing?

[JacobsonD]

I've spent the better part of the afternoon reading everything I could find in the forums when I searched for "Pilot Bearing. " Here's why. After fully engaging the clutch on the shift from 3rd to 4th while climbing a grade, I get a fairly loud growling noise when I get on the throttle. I have to really back off the fuel to get the noise to go away. In one case, I finally downshifted back to 3rd while climbing a hill towing my 7500lb trailer to get the noise to go away.



I thought it was the clutch, but I've talked to a couple of people who think it's the pilot bearing. I also notice that once in a while it's just a little tougher than normal to get into 1st while stopped, engine running. It's also tough to get into reverse while stopped with the engine running.



Is this the pilot bearing?



It's on the original clutch. A retired Cummins mechanic put in a different fuel plate. It's putting out around 225 to 250 HP now.

 

[K5IP]

After fully releasing the clutch, the pilot bearing is not doing anything. Even if bad, is should not be noisy when the clutch is released. A bad pilot usually is only noisy when the clutch is depressed.

However,

A bad pilot is consistant with difficulty engageing the transmission with the engine running. Is engagement smooth while the engine is stopped? If so, your diagnosis of a bad pilot may be correct.

Rog

 

[JacobsD]

I think that's fairly normal. Its just your motor lugging. Especially on the 3-4 shift with a wide ratio. My suggestion is to get a 3k governor spring kit and rev the motor more between those gears.

 

[GCroyle]

When the clutch is fully engaged (transmitting torque) the crankshaft and input shaft are locked together, there is no difference in RPM, no noise.



Pilot bearings and bushings are "active" during shifts and sitting at a stop with the clutch released (not transmitting torque) the crankshaft is turning and the input shaft is not, this is when the clock is ticking on the pilot bearing.



You can minimize the pilot bearing active time just by selecting neutral whenever possible at stop lights and engage the clutch until the light changes.



The noise you are hearing is most likely a load/RPM dependant gear noise being created in the transmission.



As the pilot wears out if it starts to drag the input shaft, then you can experience difficult engagement of 1st and Rev, but one other hidden cause of input shaft drag is the growth of rust on the input shaft to clutch disc hub. With time this rust grows and does not allow the disc to slide freely on the input shaft, it sticks to the flywheel and continues to rotate.



If you are looking at a high mileage original clutch, might be time to look at a new one and detail the job.

 

[JacobsonD]

Thanks for the input.



With the engine off, I can more easily slide into reverse and first than with the engine running. So this is probably an indicator of the pilot bearing getting bad from what I understand the responses to mean.



So the noise is just the transmission/driveline when the clutch is fully engaged? I'll look into the cost of the 3K kit. Is that easy to install for a guy with moderate competency wrenching?

 

[JacobsD]

Yes the 3k kit is. I tried it once, looked scary, then got motivation from an upcoming dyno day to put it in, and realized that it wasn't that bad. It was pretty easy especially if you have the proper tools. A pair of calipers, pencil magnet, and basic wrenches and sockets are really all you need.



My opinion is the 3k kit is the best 100 bucks to spend on a 12 valve.

 

[KYOUNG]

If your pilot bearing is toast, you run a good chance of whipping the input shaft bearing out..... been there done that!!!