JasBass

Happy 4th!

Took the car out for a ride this morning and sure enough, holiday mood killer . Running through the gears spirited, not hard, when going into 6 to highway cruise, I heard what sounded like a buzzing start. No issues going into the gear, no sticking, grinding, etc.. When slowing down for a stop sign, I could hear the noise even better and man was it loud. The best I can equate it to is the sound brake squealers make when pads are low, but all the time when the clutch is engaged. The car will make this at idle, in neutral, when it is not moving, so wheel bearings, U joints, and other driveline parts are eliminated.
Crawling under the car, it seems to be coming from the gear box, enough that when i'm down there, it almost drowns out the sound of the L98 with Flowmaster 40s. The sound increases with revs in neutral with clutch engaged. Sound will stop when clutch is depressed, but you can hear it begin to slow down and then disappear. It does not disappear instantly when the clutch is depressed like the normal ZF gear rattle. In neutral, I can access all gears without sticking. I used recommended redline gear oil and I changed that about 1,000 miles ago and its been butter up until now.

So to the gearbox novice, this sounds to me like it is a bearing or race in the box... Thoughts?

mike1990

You may have a failed throw out bearing. They are not available. I found one in Florida from White racing. Very expensive. If you used 90w gear oil in your transmission you may have caused some problems. This transmission uses GM 5W-30 or BMW 10W-60. Sounds odd but that is what is required. Check ZR-51 Performance web site. Bill is the foremost authority on the ZF transmissions. Even GM uses his services

Mike

JasBass

I forgot to mention I had the FW and PP replaced with a SMF unit (yes, sprung hub clutch disk lol). That has about 1,000 miles on it no issue. TOB had crossed my mind. But since the bearing itself spins constantly, shouldn't the noise be constant regardless of clutch position? As the FW and pressure plate constantly spin, even if the input shaft is not turning, the pressure plate/TOB should be spinning around it. Conceptually the same for the pilot bearing that was replaced.

I look on the tech pages of ZFDoc and see if there is anything there. I'm definitely concerned this is bearing internal in the box, especially since it sounds like the noise is biased to the rear of the box.

mike1990

So you have been down the " part no longer available " road. Also possible the pilot bearing. I had a similar issue. Took out the transmission. Was sure it was the TOB. Read all about the struggles people had with getting the Pilot bearing out. As I was removing the transmission the Pilot bearing fell on the floor. It was very loose inside the bearing pocket. Bill indicated the PB would make noise when loose like that . Also it wore the PP on the edges severely due to this issue. New Pilot bearing, TOB, PP put all back together last week fired up the car while on jacks ( wanted one last clutch bleed) aaaannnnnddddd, Water pump started screaming!! Pulled that out and sent it for rebuild. I will never put made in China junk in my cars.

Mike

JasBass

I got it to the shop this morning and we looked it all over under the lift. It's definitely not the TOB or pilot bearing. It's biased toward the rear of the box. We're thinking one of the needle bearings on the countershaft has given it up. Tracking down some shops local that can open it up and replace. Thankfully we are in NC race shop country here. But I'm also going to shoot off an email to ZF Doc for a quote on maybe beefing it up some. I'm in this funky time now with the car where I have build plans for it, this might just have accelerated that timeline. I've been eyeballing a nice 4 bolt 396 miniram setup and EZ EFI 2.0. Now to just put a kidney on the black market