Blue tag or a black tag? What is the P/N on the trans?


helphos, the syncro going out is related directly to clutch Hydraulic system failure. The clutch hydraulics needs to be at 100% or syncro damage will happen. This could be a case of just old & worn out hydraulic parts. I would suggest a trip to zfdoc.com for the skinny on the zf6spd from the Man....Bill B.


Tom

 

Thanks for the comments and insights to The Blur, GregPenn and Tomtom!
I expect to be completing the purchase of this 93 Vette within the next two weeks. I've been reading other threads, and agree that I at least have to replace the slave (The master is showing no signs of leakage, but others are advising replace both--any opinions?). My concern was that I might get a 'new' slave with the 'old' problem (reversed seals, which I would have to disassemble to check and fix)). It also looks like the fluid must be Valvoline Synthetic DOT 3-4 brake fluid, right?

Finally- any definitive info on what color my trans tag is? I will definitely crawl under at my first opportunity to check visually, but I am sure it is original. I have seen many posts that the black tag ZF went through the end of the 93 model year. but a GM TSB that says the blue tags began with the 93 model year. Since mine is (will be!) a '93, that is critical to know, because I would like to avoid dealing with the clutch if I can help it, and replacing like with like will be least costly (I think).

and REALLY Finally, thanks for responding to a thread that has been in suspended animation for several years!! http://images.ibsrv.net/ibsrv/res/sr...ies/yesnod.gif

 

Helphos,

Not a problem man. This is very important to all of us C4 owners with zf6spd's.

Link to Bill B's web site. Please go and do some reading, it's stuff every zf driver needs to know! http://zfdoc.com/

Yes, according to Bill any time any part replacement is done on the hyd system, it should always be done in master/slave pairs.

Fwiw, GM has made all C4 hyd parts NLA from the factory. This was a response to them being called to account by Bill B and his supplier ( a big chevy dealer ). GM was to talk with the original contractor responsible for the re-supply mfg'ing, TRW I think, to figure out what went wrong and how to fix the issue. That was the last anyone heard about what GM was doing to look into the issue. The next thing that happened was that all the zf6spd hyd parts became NLA from GM. The aftermarket is now the only source for our slaves & masters.


Tom

 

Ditto on the suggestion to visit Bill Boudreau's zfdcoc.com web site. There is loads of info in there on the ZF trans and related items and Bill is a master of knowledge of that stuff.

I replaced my original ZF with a blueprinted unit from Bill a few years ago (after a few too many burnouts in the Carlisle downtown parade ) and needless to say, it has performed flawlessly since then.

ZF 6-speed trannys are still available from a few sources, but good luck trying to find a stock dual mass flywheel/clutch assembly. If you come across one, I suggest you buy it and hang on to it.

 

I like Bill and think he provides some good advice. OTOH, I like to double-check his (or any other person's advice). Why? Because they may be inconsistent in what they say, temporarily forget something, or learn something new.

For example, on one page of Bill's website, he says this: "Pay attention to the clutch hydraulic system. 85% of the ZF 6-speeds (S6-40) that come across my bench are in for service due to early failure due to improperly maintained hydraulic clutch systems operating in a degraded condition. Don't hesitate to replace the slave cylinder when it no longer bleeds out and (doesn't trap air/moisture for several months) operates perfectly. Prepare to replace the clutch master hydraulic cylinder once for every 2 slave cylinder replacements. The hydraulic clutch system must always operate in the 97+% efficiency range to provide for normal transmission life expectancy (75,000 - 150,000 miles) based on demand usage."

On another page, he says this: "The clutch hydraulic master and slave cylinders should be replaced as a set." This statement is obviously the more conservative advice of the two but indicates slaves might fail at a higher rate? Maybe they fail faster as a result of being attached to a hot tranny (vs the master up on the cooler firewall?).

A few yrs back, Bill described the problem as a disintegration of the rubber components in the clutch hydraulic system as a problem. When rubber particles degrade into the fluid, they act as abrasive particles to speed up wear/breakdown of the seals/cups. I suspect most of that debris settles at the bottom of the system -- in the slave cylinder. Maybe that's why he initially posted a 2 for 1 swap rate. But, once problems become serious, it's better to swap everything. That includes slave, master, and the connecting hose.

Remember the OEM hose is also made of rubber. As such, it can degrade (from age) and induce it's own contaminants into the system.

Compared to the potential cost of replacing the synchros, doing everything can't be bad advice.