So I already had one ZF6 replaced back when the car was under an extended warranty, but now this one has gone bad! I was hearing a nasty sound that I thought was the throw out bearing, but after replacing it, the noise still exists. It is definitely coming from inside the tranny, and the best way to describe it is to say it sounds like it is running dry and grinding(but obviously the fluid has already been checked). When I had the first problem, it was as simple as a bad bearing, but at the time(4yrs ago) GM did not sell parts for it so they just replaced it. Now the trans is discontinued. Do ya'll know any place you can get parts for them so it could be rebuilt?

Thanks so much for any help,

Brian

 

Do a search for ZFdoc. I haven't had him do any work for me but there are tons of people on here that swear he's the shiznit. He has a website too. Another option is to hit ebay and look up a seller called "thepartsladi." I paid $1390+around $175 for shipping of a brand new blue-tag ZF.

ZF doc can rebuild it to a racing spec and I think he told me he charges around $900 to go through a brand new one. No idea about a used one. I am assuming the same price plus parts.

Also google white's racing in florida. They had some ZF's too, and he didn't think a new ZF needed to be gone through. Best of luck to ya!

 

wow, you have really bad luck! Well, that or you race it.... ZFdoc's treatment may be a good idea if that's the case.

 

$900 to rebuild?? That wouldnt be too bad.

Most I hear spend a couple grand with him on a rebuild. Sure he could give you the particulars depending on what you want to do. personally Id buy a new one and be done with it, much cheaper.

 

Pardon my Q, not intending to be insulting to you.:o

This grinding noise that you hear, does it happen when you put the clutch pedal down and are trying to shift say from 2nd to 3rd?

Does it happen when you are stopped & in a gear with the pedal down, like at a stop light waiting?

Does it happen if you are stopped and try to go from neutral into 1st, or any of the first 4 gears?

Since this noise appeared, is it hard to get 1st or 3rd from neutral w/ motor at idle?

With the motor off & cold, can you go from which ever gear you left it in, right to reverse no problem, or does it want to fight you? Like you parked it & left it in 1st...can you jump in and grab reverse & it goes smoothly?

If any of those symptoms are what you are having to deal with then the issue maybe with the hydraulics. The noise you hear could be the dog teeth on the synchros hitting due to a loss of hydraulic pressure in the system....bad slave, master, or both....or just low on fluid, but where did the fluid go...usually a leak somewhere.

Just some of the stuff I had when my hydraulics went out & GM was selling a bunch of deffective replacement parts.....took me a long time to find good parts so I could have my car back.


Tom

 

http://www.rsgear.com/zf.asp

www.zfdoc.com

 

He quoted me that on the phone for the brand new trans to be gone through. He also told me that with a used one it can snowball really fast. So, $900 was for him to work a NEW transmission.

 

Tomtom, to answer your questions, the sound can be heard with the engine idleing and foot off the clutch, as well as in any gear from about 1000 to1800 rpm and then again from about 2500 to 3500 rpm or any time it is under a good load, say putting it in 6th and giving it some throttle to accelerate. The hydraulics are brand new and I do not have any problems shifting through the gears at all.

Brian

 

A rebuild with new parts right now will be very expensive, the retail cost of a synchro kit for a ZF was recently raised to over $800, and that just the synchros.

Bill at ZFDoc just got some brand new ZF transmissions in last week, might want to shoot him an e-mail and see what he can do for you.

 

Cut your losses and get a TKO 500 or 600

 

I had my transmission redone by ZFdoc some time ago. It was not the cheapest thing, but it has performed flawlessly. My car has been autocrossed and drag raced a lot and it driven in a spirited manner.

I would suggest going with cryo treatment on all the replacement parts. ZFDoc goes through the transmission and determines how worn the syncros are and only replaces the parts that need replacing. He set up the shift springs to be equal pressure on all the forward gears.

There is a shop here in Austin that does work on them, Pistole's, in far South Austin. The shop is nothing to look at but they have been around for years.

Matt

 

Thanks Brian for not being insulted at my Q's. Did they change the pilot bushing/or bearing (some C4's used a needle type pilot, not sure which zf6 cars got that.) because you can hear the pilot bushing at idle, trans in neutral & pedal up. The needle types make even more noise than the bushing types. I believe that there was a TSB on customer complaints on that issue, but the needle type was really loud and the bushing type less so.

If I follow you right, your noise happens under specific circumstances?
The 1k to 1.8k & the 2.5k to 3.5k, does the noise intensity vary with the rpms?

If my 6, if it is cold & I try to use 6th w/a load I get some strange noise but the fluid is cold and it ceases after full warm up.

I'm gonna say two things that are fairly simple to check & two things that ain't so simple to check.
Loose heat shields & loose C-beam bolts.
Miss-aligned C-beam & inner shifter boot not installed correctly.

I'm not fluent in zf6 but over at zfdoc.com there is a lot of useful Q & A on our transmissions....stuff ya can check yourself & complicated stuff if you have the tools & work space. Go over & give a read and even if you e-mail Bill you will get an honest long distance diagnosis....he's a stand up guy.

Sorry I don't have an answer to your issue.:o

Tom

 

Are they suppose to be stonger?

 

I have just a couple of thoughts. When I got my LT4, I had never even heard of a zf6. I noticed a winding/grinding noise after I got it. I thought something was wrong with the tranny. Shortly after that the clutch went out. Turned out the clutch fork pivot was backing out which toasted the clutch. (being a rookie on the six speed probably didn't help either). I figured the noise would go away with the new cluth assembly. Nope. Then I learned that this noise is inherant in the zf6. "Gear chatter". Happens at idle with the clutch engaged(pedal up). This is why GM used the dual mass FW. It's normal. Perhaps you already knew this and this isn't your problem.

But, after awhile, I suddenly heard a rattling noise when I pushed the clutch pedal all the way down. Turns out the clutch fork was putting grooves in the pivot ball. This made the clutch fork rub on the pressure plate. It also made the clutch not fully disengage, thus increase noise.

As far as the noise in gear, in first through third I get a little whine. everything I have read & heard tells me it's normal zf6. As far as sixth, that gear is not really designed to accelerate in, at least not in bunches. I too get a little groan when I try it, but that's going to happen. If I accelerate very gradually it doesn't happen.

Like I said, perhaps you already know all of this, and it doesn't apply to your situation. I just thought I would throw it out there because there was a time when I didn't know it.

 

5-speed,, 500 Ft-lb/TQ or 600 Ft-lb/TQ

 

If you have an aftermarket, single mass, aluminum flywheel, you will have a strong rattling noise at idle in neutral with the clutch disengaged (pedal up); if you push down on the clutch pedal and the noise stops, you have an aluminum flywheel (single mass). This happens b/c the flywheel does not dappen the noise of the ZF like the factory dual mass steel flywheels; just annoying but normal.

 

Do they have a 6 speed? How much are we talking? Does it bolt up?

 

Email ZFdoc with a decription of you problem. Your problem sounds very similair to my current problem. It could be a worn out pilot bushing. A bad pilot bushing can cause some noise in the transmission that sounds just like a bad throwout bearing. Talk to ZFdoc, he will help.
93cruiser

 

I bought a brand new zf-6 Blue tag and sent it to Bill at ZFDOC. A race rebuild with better bearings, laser welding synchros etc etc and the trans shifts and drives better than my old black tag or new blue tag ever did. 8000 rpm shifts for over a year and a half and it still shifts and sounds like new.

 

Brian,

The countershaft front bearing shim thickness is not thick enough to disallow slight longitudinal movment of the bearing within the bearing journal. This allows the countershaft assembly to move slightly in the longitudinal axis which in turn allows the occurance of harmonic related gear buzz.
Installing the thickest ship possible at the countershaft front bearing should fix problem.

Does the vehicle still have dual mass flywheel and stock clutch configuration?
When was the pilot bushing (or bearing) replaced last?
If bushing type, was grease applied to input shaft pilot tip and or bushing when installed? this is not good for lungevity of the pilot bushing. Grease dries up and clogs pours of pilot bushing reducing self-oiling characteristic of oil impregnated bushing.
This can cause problems with glaze build-up between pilot bushing and input shaft pilot tip leading to accellerated wear of the pilot bushing.
We recommend using Fluted pilot bushing (GM P/N 10125896) regardless if clutch is replaced when replacing the transmission.

I'll check in on this thread periodically to see Brian's replies to these questions and go from there. Just want to make sure you don't end up spending more than you have to to fix problem.

By the way folks, with the new ZF S6-40 transmissions, we charge $600 labor to balance and blueprint plus $100 small parts required. With used ZF S6-40 units, labor is $840 plus parts which we all know are very expensive.

Best regards,
Bill Boudreau (ZFDoc)
ZR51 Performance
(602) 319-6575