Which oil in the gearbox ?

[ghlkal]

Originally Posted by Hib Halverson

The Castrol 10W60 is an acceptable choice but while Bill the ZF Doc likes it, that lube needs to be changed frequently.

What would be an acceptable change frequency?

[VetteMed]

I think I remember reading that 10-12,000 miles is about the maximum before the viscosity drops below a "safe" range.

[Paul Workman]

Originally Posted by VetteMed

I think I remember reading that 10-12,000 miles is about the maximum before the viscosity drops below a "safe" range.

Yeah, I believe it could have been on Bill Boudreu's ZFdoc.com site where that was mentioned.

I put 12k miles on my Z in 4-1/2 seasons. So, I guess changing it "often" is a relative thing - depending on driving.

Maybe Marc Hiabeck can chime in here on this change iterval too. If I recall, Marc has a different opinion regarding oil change itervals for the ZF, as well as an opinion on what to use in it. And, too... I recall where he tells of a guy in France that had his ZF freeze up on him while cruising in his 95 ZR-1. (That makes two 95s; his and mine that had that problem!).

I guess my feelings on it is that at least some ZFs were/are prone to having inherent lubrication issues (to that reverse gear). So, because experimenting with different oils is practically beyond the ability of all but a tiny number of automotive engineering types, or emperical data gathered by those that repair them on a regular basis, I defer to the latter especially for input on what to use - and how often to change it.

I am damn sure I don't want to have another ZF lock up on me for lack of the "right stuff" whatever that might be! And, there is no doubt there is more than one lube out there that will meet or exceed the ZF needs. Picture this: A crowed expressway, cruising at 70 mph. Suddenly the car is decellerating as tho I was braking rather firmly. No brake lights, mind you, and no shoulder on the left side of the expressway. Engine is lugging hard in 6th to maintain cruise control input. Gotta get off this damn expressway NOW! Down shifting to 4th and give it more throttle, trying to maintain position and signal a right lane change - but still decellerating! I squeeze in front of the car in the right lane next to me, and then practically cutting off the guy in the next lane over to finally get to an off-ramp, just as the rear end locks up and brings the car to a screaching halt!!

OK, this is a rare occurance, to be sure. But, it is not unknown to this transmission, according to Bill B. And, it seems to be (from what others have said) more prevelant to 95 MY especially; including base model Vettes as well. So, I guess I'm trying to say that for me only, perhaps, I get a little nurvous about wandering off the path when it comes to lube recommendations in this application. There's more at stake than how it shifts...is my point, I guess.

Everyone's mileage may vary, I recon.



P.

[scottfab]

Originally Posted by Paul Workman

..........................
I am damn sure I don't want to have another ZF lock up on me for lack of the "right stuff" whatever that might be! And, there is no doubt there is more than one lube out there that will meet or exceed the ZF needs. Picture this: A crowed expressway, cruising at 70 mph. Suddenly the car is decellerating as tho I was braking rather firmly. No brake lights, mind you, and no shoulder on the left side of the expressway. Engine is lugging hard in 6th to maintain cruise control input. Gotta get off this damn expressway NOW! Down shifting to 4th and give it more throttle, trying to maintain position and signal a right lane change - but still decellerating! I squeeze in front of the car in the right lane next to me, and then practically cutting off the guy in the next lane over to finally get to an off-ramp, just as the rear end locks up and brings the car to a screaching halt!!
P.

Sounds a lot like the time my fuel sender stuck showing I had gas when I ran out on in the fast lane of a three lane highway. No fun cutting people off as you dive to the right for sure.

I've rebuilt a few ZF6s and the only thing I saw about the reverse rail of concern was the entry point for oil. It's vulnerable in that if you're even a slight bit low on oil it's bad news for the rail. Opening up the groove I'm sure would help but...... not a fix all. I keep my ZF6 ever so slightly overfilled.( 1 cup) And I make very sure the ZF6 is sitting level when filling it. I also use the stock GM oil (or Havoline 10w30)
Come to think of it, it's time to swap out the oil and coolant this year.

[XfireZ51]

I change my Castrol TWS about every 10,000mi. Have used it for ~ 10 years.

[A26B]

Originally Posted by Paul Workman

................ And, too... I recall where he tells of a guy in France that had his ZF freeze up on him while cruising in his 95 ZR-1. (That makes two 95s; his and mine that had that problem!).

...............
I am damn sure I don't want to have another ZF lock up on me for lack of the "right stuff" whatever that might be! And, there is no doubt there is more than one lube out there that will meet or exceed the ZF needs. Picture this: A crowed expressway, cruising at 70 mph. Suddenly the car is decellerating as tho I was braking rather firmly. No brake lights, mind you, and no shoulder on the left side of the expressway. Engine is lugging hard in 6th to maintain cruise control input. Gotta get off this damn expressway NOW! Down shifting to 4th and give it more throttle, trying to maintain position and signal a right lane change - but still decellerating! I squeeze in front of the car in the right lane next to me, and then practically cutting off the guy in the next lane over to finally get to an off-ramp, just as the rear end locks up and brings the car to a screaching halt!!

OK, this is a rare occurance, to be sure. But, it is not unknown to this transmission, according to Bill B. And, it seems to be (from what others have said) more prevelant to 95 MY especially; including base model Vettes as well. .....................
P.

It happened on my 94 @ about 65K miles. I was cruising in town, first noticed at stop light, like the brakes were dragging. Started home, getting more noticable. 2 miles from home, inside lane of city street, seriously pulling down @ abt 30mph. Even the 415 wouldn't pull it to get to the side of the road. Had to get a roll back to take it home. jacked up the rear & pulled it to the 4 post lift, then when it got on the ramps, i oiled the ramps in front of the tires & winched it the rest of the way.

I know of a 91 that it happened to also. Bill B. gave me the same explanation with a little discussion on lube. I drained the factory fill, which looked good, & replaced with Redline about3K miles before the failure. Bill said he's heard of 2 other failing after changing to Redline. I use the Castrol now.

Having that failure on a multilane highway with traffic, like Paul, would be scary. Could easily happen in a traffic lane if you didn't react very quickly.

[WVZR-1]

In these instances of "lock-up" what internals of the transmissions were actually damaged and required replacement?