Your ZF6 makes noises or won't shift, what to do?

[tccrab]

Your ZF6 has problems, what are your options?

Chapter 1.

Replace or Rebuild?

Replace:
GM no longer supports the ZF6, so taking your car to local Chevy dealer isn’t all that great of an idea.
In fact, GM sold off its entire inventory of new and rebuilt ZF6’s several years ago, so your dealer would have to locate a rebuilt unit from a GM authorized rebuilder. He will of course add on a sizeable markup and a “stocking fee” so figure on paying double for the transmission. And don’t forget that the mechanic replacing your ZF6 has likely never seen a ZR1 before, so you will be paying top dollar for his “On The Job Training”. Luckily, replacing transmissions isn’t exactly rocket science, so you’ve got a 50% chance that he’ll get it right.

Most of the new/old stock ZF6’s that GM sold off would up in private hands.
I was able to track down at least 7 of the new/old stock ZF6’s during my search so they are out there, for now. 5 years from now, who knows?
The current market price for a new/old stock ZF6 runs between $1800 and $2500.
Be sure to add in at least $250 for shipping unless you are fortunate enough to locate a unit local to you. Shipping weight is approximately 220 pounds if the ZF6 is shipped in its original packing crate and pallet.

Rebuild:
ZF Industries has long since sold the ZF6 S640 product line to Rockland Standard Gear Inc. located in Sloatsburg NY.
http://www.rsgear.com
“Rockland Standard Gear is the only ZF-certified distributor/ remanufacturer for the S6-40 6-SPD transmissions found in the 1989-96 C4 Corvette. We remanufacture this transmission for ZF and GM. Call for information on getting your unit rebuilt.”
Their current price for an exchange ZF6 is $1895 plus shipping. They give a 1 year warranty on parts and labor. There is a $500 core charge if you don’t send back your old transmission. They will rebuild your transmission, but the price will depend on what is wrong and what they have to replace.
Parts for the ZF6 are VERY expensive.

Bill Boudreau, the “ZF Doc”; http://www.zfdoc.com does rebuilds and performance upgrades. He’s in Cave Creek AZ, a nice little “Artsy Fartsy” town outside of Phoenix. It's where Cave Creek Chili Beer with the jalapeno pepper in it comes from. Stay away from it at all costs(the stuff is Nasty!!).
His prices range from reasonable to not so reasonable, depending on the cost of parts, whatever upgrades you might want, and the time he spends on it.
Bill is a great guy and a wealth of information. I can't thank him enough for his guidance and patience in answering all my phone calls and emails and tolerating all my stupid questions.

Other Rebuilders:
There are other rebuilders that advertize that they rebuild ZF’s. I don’t know much about them. There’s a list over on the ZR1 Net Registry here:
http://www.zr1netregistry.com/ZR1_faq.htm#44


The ZF6 S6-40:


There are two versions of the ZF6; the “Black Tag” which was installed on 1990-’93½ model year ZR1’s and the “Blue Tag” version which was installed in the ‘1993½ -‘95’s.
Black tag units were assembled in Germany.
Blue tag units were assembled in the United States.
Black tag units are rated to 450ft/lbs torque, blue label units are rated to 400ft/lbs.
The contact ratio was increased in the blue tag units so as to reduce the “Growling” noise common to the black tag units.
The later model ZF6s do not have a Reverse Lockout Ring below the shift knob. They have a “Crash Through” to reverse that takes about 15lb of force to engage the reverse gear.

There are a few other subtle differences between the black tag and the blue tag:

• The speed sensor plug is different on the blue tag.
• The tailshaft does not have two holes drilled and tapped on the drivers’ side to mount the exhaust hanger on that side.

Rather than finding a new plug which I’m told is still available through GM, I just transplanted the speed sensor from my black tag into the blue tag.

Luckily the exhaust hanger has two bolts on the passenger side, so no problems there. I bent the drivers’ side away from the transmission a little so as to reduce the chance of vibrating against the transmission.

The ZF6 S-40 that is in the ZR1 is nearly identical to the one in the L98 & LT1 cars with the exception of the input shaft.
The input shaft on the ZR1 transmission is 190.5mm and the non ZR1 is 159.5mm.
The good news is that the input shaft from a ZR1 transmission can be installed into a non-ZR1 ZF6 relatively easily by most transmission shops.
There were significantly more ZF6s put into L98 & LT1 cars so it’s a lot easier and less expensive to find a non-ZR1 ZF6 and swap the input shaft from your old transmission into the new one.

Stay tuned for Chapter 2.
Removing the ZF6 at home, or...
"Honey, where's the Band Aids, and while you're in the medicine cabinet would you get me the BenGay?"