Just picked up my 1988 F350 7.3 with a new clutch. It is a single flywheel? clutch instead of the original dual flywheel. Part of the object was to make the clutch pedal lighter - and it sure did. However, at low speeds and low rpms there is a grinding or rattling noise that mostly goes away if I push in the clutch pedal. This is a new noise. What do you think is the problem?

 

It sounds like what you are experiencing is "gear rollover", which is completely normal with a single mass flywheel. No worries

 

That's good to hear. Since the truck has so much torque we've been lazy about shifting - running in third when we should be in second. Now if we do that we get the grinding rattling sound. Still sound like no problem to you? If we push in the clutch or shift to a lower gear the rattle is much less or goes away.

 

My 1990 F250 with the ZF 5-speed behaves the same way.

 

At this point, if no one thinks this is abnormal or I'm doing damage, I'll just drive it. I need to pull the trailer this weekend. It'll be interesting to see if that's better or worse.

 

Even after having my ZF5 rebuilt, I still experience gear rollover noise. If it happens with the engine running and transmission in neutral, or when you lug the engine while in gear then it is completely normal.

Just to make sure, it sounds similar to a can of marbles correct?

 

Right now it only makes the noise when lugging in gear - usually at too low an rpm for the gear. We are running a synthetic transmission fluid to try to reduce the noise. Any other suggestions on fluid, additives, etc?

 

I added the Lucas trans oil product (drained out about 16 oz of the ATF first).
It made a slight difference. The rollover noise is something you get used to- mines been doing it for many many miles....

 

Thank you.