Paul Workman

One experience does not a trend make. So, to be so adamant, perhaps you can enlighten us by have something in the way of scientific data; something other than singular anecdotal experience? Bill's reputation regarding the ZF is well established and is one of the best supporters of the C4s.

Truth is where you find it, so if you have some data to dispute Bill's position/recommendations, won't you please share it??

PS: For the record: you don't assure me. If anecdotes amount to scientific proof in your book, then my experience with Bill's advice has been just the opposite; including the Catrol TWS recommendation (which has worked perfectly in both of my ZF6s since 2003, one behind a stock LT1, and the other coupled to a 500+ chp LT5 often shifting at over 7200 rpm over the last 5 years - with NO problems). Just sayin...I wouldn't be so quick to impugn one of our best supporting vendors, especially with nothing more than one man's opinion on it...would be my suggestion.

Just sayin...

lt4obsesses

The very first time I went to change the fluid, I went to a BMW dealer to aquire their stuff. The parts counterperson had absolutely no idea what I was talking about. I wound up just going with the GM stuff from my local dealer that time. After that, it's been Amsoil.

mike100

I'm running the Amsoil syncromesh because the BMW 10w-60 was catching or notchy in 3rd gear. If the ZFDoc told me he wouldn't warranty my ZF due to that, I'd still run the Amsoil. I do feel that it might be a good idea to change it every two to three years just in case viscosity shear thins it out too much.

My old 95 blue label coupe also shifted like butter on the factory fill which, I'm told, is a Texaco 10w-30 manual trans formulation. Same oil weight, same good shifting.

70ZZ3 96LT4

I have never changed the lubricant in my 96's transmission and being the original owner with 40K original miles on it I have let the owners manual be my guide on changing.

Richard Raichert

My 94 owners manual states that: (has never been changed, has 25000 miles.

Manual trans fluid "doesn't require changing".
Fluid is 5W30
For a rebuild it holds 4.4 pints or 2.1 L

Amsoil or Castrol is a heavier viscosity, is that ok?
If I do change do you get the full 4.4 or 2.1 L?

Change or not? Opinions welcome!

scotth48

Changed both trans and differential on my '93 at 96,000 miles and used Recommended oi by AMSOIL in both.

RollaMo-LT4

4.4 Pints is approx. 2.1 Liters.

Up to you if you change it or not.
None of the actual spec'd fluid is available anymore, as it has been replaced with newer part numbers.
Is it the same fluid or not? No way of knowing.

I am sticking with the Amsoil fluid I posted earlier.
It is listed as meeting the GM Spec for part number 1052931

DGXR

Change it. Be sure to loosen the fill plug FIRST, so you know you can get the new stuff in after the old stuff comes out. There are bound to be some metal particles floating around in there after 25000 miles, and those are not good for the needle bearings and other fine parts inside that 6-speed. Sure it's not going to blow up or fall apart if you don't change it, but changing it is cheap insurance that it will last as long as possible.

Heavier viscosity is OK, but keep it as close to 5w30 as possible. The gears will shear the viscosity down slowly over time. But no 20w50! LOL

I'd suggest either the Amsoil synchromesh manual transmission fluid 5w30, or the Pennzoil Synchromesh which is not synthetic but is 5w30 (I have used the Pennzoil on two different ZF6 with good results).

emptnest

I just changed the fluid in my 1993 which I purchased in May with 42,000 miles. I assume that this was the first oil change for the zf6 (black tag).

Went with Amsoil synchromesh. It made a difference. Very smooth now.

dizwiz24

I didnt need any so-called scientific data pulled-out-from-who-knows-where to tell me that my car wasnt acting right after I swapped to the supposedly smoother shifting castrol tws 10w-60 bmw m5 engine oil.

I will report my experiences (again) as the synchronizers not working. Shifting was very notchy during normal driving. I couldnt even physically engage the next gear during WOT operation. I had to abort dragstrip runs, letting slower cars beat me because the lever would not move.

I got into contact will Bill about it, he suggested my clutch hydraulics were shot, so I spend a couple hundred bucks and replaced those - being careful to properly bleed the slave cylinder.

That didnt fix a thing.

Bill's next suggestion was that I need a trans rebuild at a cost of thousands of dollars.

I simply drained the castrol tws 10w-60, noting lots of bronze/copperish colored flecks in the 10w-60 fluid that came out. Note the castrol fluid was in there for maybe 200-300 miles tops.

I replaced it with GM syncromesh and all the problems went away like magic. So much for need to spend thousands on a trans rebuild.

I have since replaced the GM syncromesh, routine mainentance during a clutch swap, and noted virtually no -zero- bronze/copper flecks in the fluid drained out that had been in there about 20000 miles.

The scientific evidence you state that bill has in his outdated website tells you nothing about how it performs or interacts with the zf transmission syncronizers.

Its like its tells you that a color spectoscopic analysis identifies the fluid is amber.

It is useless information.

I am not taking away from Bill's knowledge or dedication to our cars transmissions. Bill has been very helpful to me on certain issues and knows his stuff in certain areas.

The castrol 10w-60, again is suited for a bmw engine.

You wouldnt run syncromesh in your bmw engine, so why run bmw engine oil in your transmission?


Now: Is there something weird about my transmission (and the others who have had issues with the castrol fill)? I cannot answer that.

Paul Workman

Yours is an Interesting experience, but my point is it is anecdotal at best. In your case, it is what it is. But, to be sure, the kinds of problems you've experienced are NOT representative of all ZFs by far and one example (yours) is certainly not statistically valid enough to cast dispersions on Bill or his recommendations...at least not yet.

All I'm saying is, if your solution "fixed" your problem, great. I'm talking about the Scientific Method: To "cast dispersions" by stating "BS" on a set of statistically valid, albeit contradictory data, based on that one example - especially without allowing for some anomaly making your example unique somehow, is NOT a statistically valid argument.

Now... Because shifting into 5th gear has always been a little "notchy" on my Z's ZF, I mAy just give that GM Syncromesh you recommended a try.

Deakins

I would switch it over. When I first got my 93 I changed all the fluids to set a baseline and went with the much talked about Castrol BMW fluid (at like $15 a liter?). I immediately noticed that the car started shifting like crap (especially when it was cooler/cold in the mornings) and in many cases felt like the shifter was hitting a wall inside the transmission. I flipped through my FSM when it showed up shortly there after and found that they spec'd a 5w30 engine oil; I went to a friend of mine who is a GM tech and explained the situation to him and he thought I was nuts for pouring a 10w60 anything into an application that required a 5w30. I switched to and have since run several of the above mentioned products (in 5w30) and have never again experienced the nasty shifting that I ran into with the Castrol BMW stuff.

Say what you want but at least up in the cooler mid west that was not the fluid to have in this transmission. Just my .02

dizwiz24

Thank you.

It is not just a viscosity issue (ie. You cant just use plain 5w-30 motor oil in the trans either)....

There are some modifiers or something in the correct fluids (either the zf factory fill 5w30 based stuff or the gm shyncromesh or amsoil syncromesh), making it suitable for a transmission.

Im going to take a wild guess here and say the issue is the castrol fluid is too slippery For the synchros.

There needs to still be a tiny amount of friction for them to work right.

Im not a scientist though.

I would love for bill to get on here and try to explain his misguided suggestion and why it has done us all so wrong.

aDigitalPhantom

When I changed the fluid in my ZF6 I used the AMSOIL mentioned here. I had looked to see if there was a local place to get the BMW variety talked about here, but there was not. I could get the GM syncromesh from the local GM dealer at $30/quart, or the AMSOIL for $10/per quart@NAPA. At the time I had read more good things about the AMSOIL, and went with that.

Deakins

But I think that it does come down to viscosity on this at least to some extent. If you ever have one of these transmissions apart; we did at tech school back in the day, you will see that the synchros fit up nice and tight on their parts of the gears (it's literally a friction application) and there isn't much room for the thicker oil to get in there IMO (and have you ever felt how sticky that stuff is??).

The Castrol fluid probably works great down by Phoenix in the super heat where Bill operates but I can say up in Iowa where I operate the 10W60 (I still have partial bottle sitting on the shelf that I show people as it is some very trick oil) is thick nasty when it gets cold. And that is exactly when my transmission did not want to function properly. Get it up to the high end of operating temps and it still didn't feel great, but it felt pretty normal. Just my .02

dizwiz24

ill agree the cold makes it worse but my dragstrip issues really confused me.

The dragstrip is a 50 mile drive.

you would have thought it would have been warmed up by then.

Apparently not