ZF6 oil question
Thread Starter
Racer
Joined: Oct 2007
Posts: 338
Likes: 0
From: Kansas City Missouri
ZF6 oil question
My brother looked at a 94 C4 today with the 6 speed transmission. The price is right and the owner just changed the fluids so he purchased the car for 5k.
When I was looking over the receipts he had with it, I noticed he has been using Mobil Synthetic 74w90 in the transmission. I thought these transmissions needed a lighter weight then this...is this something he needs to get on the ball and change?
Thanks
When I was looking over the receipts he had with it, I noticed he has been using Mobil Synthetic 74w90 in the transmission. I thought these transmissions needed a lighter weight then this...is this something he needs to get on the ball and change?
Thanks
Last edited by nada1; Oct 24, 2009 at 05:47 PM. Reason: spell
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
My brother looked at a 94 C4 today with the 6 speed transmission. The price is right and the owner just changed the fluids so he purchased the car for 5k.
When I was looking over the receipts he had with it, I noticed he has been using Mobil Synthetic 74w90 in the transmission. I thought these transmissions needed a lighter weight then this...is this something he needs to get on the ball and change?
Thanks
When I was looking over the receipts he had with it, I noticed he has been using Mobil Synthetic 74w90 in the transmission. I thought these transmissions needed a lighter weight then this...is this something he needs to get on the ball and change?
Thanks
The OEM lube has been discontinued (from what I've read). The BMW lube is pretty heavy too. Plus, the measure for a gear lube isn't on the same scale as engine oil. IOW, a 75w-90 lube is closer to 30w engine oil than you think.
Any of the products (besides the BMW lube) will also be a 75w-90 anyway. Lots of people are running them.
Burning Brakes
Joined: May 2007
Posts: 965
Likes: 13
From: turn 12 at Road America or TX
Look here: http://www.zfdoc.com/
I'd get that Mobil synthetic out of there right away. Back when this tranny was new in
ZR-1s there were synchro failures because the Mobil synthetic at the time was too slippery.
Replace it with the BMW stuff according to zfdoc, or just get what replacement oil GM is selling today.
The original stuff you can't get anymore was a 5W-30 engine oil with friction modifiers for use in the ZF6, and it was made by Texaco.
I'd get that Mobil synthetic out of there right away. Back when this tranny was new in
ZR-1s there were synchro failures because the Mobil synthetic at the time was too slippery.
Replace it with the BMW stuff according to zfdoc, or just get what replacement oil GM is selling today.
The original stuff you can't get anymore was a 5W-30 engine oil with friction modifiers for use in the ZF6, and it was made by Texaco.
Last edited by gbrtng; Oct 25, 2009 at 03:32 PM.
Thread Starter
Racer
Joined: Oct 2007
Posts: 338
Likes: 0
From: Kansas City Missouri
That is true, but did they not use regular Mobil motor oil then, where the stuff today is 75v90 gear lube? (syn)
I have no idea myself, as I use amsoil, just throwing this out there.
I have no idea myself, as I use amsoil, just throwing this out there.
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Castrol is the only ZF-approved lube left. Keep in mind though, that ZF is NOT in the business of keeping this list up-to-date. Neither is GM for that matter. (In fact, I wouldn't pick the replacement GM lube. I suspect they're just pushing something across the counter at you -- because the "correct" stuff isn't available anymore!) What this means is there are acceptable fluids that haven't been tested for our application. And, they NEVER will be.
I don't remember exactly when the ZF rights were sold, but the info on this transmission is definitely into the try-it-and-see stage.
I've posted 2 or 3 extensive threads on the subject (after contacting ZF for guidance). After doing so -- and seeing what people are successfully running -- I came to the conclusion that modern-day synthetics should be fine. (Like AMSOIL, Royal Purple, Mobil shockproof, etc...)
Use the search function to get existing background on the subject.
I don't remember exactly when the ZF rights were sold, but the info on this transmission is definitely into the try-it-and-see stage.
I've posted 2 or 3 extensive threads on the subject (after contacting ZF for guidance). After doing so -- and seeing what people are successfully running -- I came to the conclusion that modern-day synthetics should be fine. (Like AMSOIL, Royal Purple, Mobil shockproof, etc...)
Use the search function to get existing background on the subject.
Last edited by GREGGPENN; Oct 25, 2009 at 08:44 PM.
Pro
Joined: Sep 2004
Posts: 505
Likes: 1
From: Guntersville Alabama
Do not run the GM replacement oil. Take Zfdocs advise and run the BMW oil. I tried the GM stuff first and found lots bronze metallic particals in the oil. The BMW oil gave me a quieter and smother shifing transmission. Just my two cents.
93cruiser
93cruiser
Race Director
Joined: Jan 2002
Posts: 12,261
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From: O'Fallon Missouri
GREGGPENN is right with a 75w90 gear lube being close to a 30w motor oil, they are measured on a different scale. Also, the factory fill for the ZF6 was a 5w30 motor oil with some additives, not the BMW Castrol.
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Thread Starter
Racer
Joined: Oct 2007
Posts: 338
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From: Kansas City Missouri
wow...seems to be no clear answer on this one...everyone has an opinion, if you use the search, it seems it makes no difference what you run, some people don't like it, even the BMW oil.....
Drifting
Joined: Oct 2006
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From: Romeoville IL
For what it's worth.
Race Director
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From: NEwhere Ohio
I do not agree with zfdoc's recommendation on the bmw castrol oil. I used this stuff and constantly found I was grinding gears. It was like the stuff was too slippery for the synchros. In some cases, I had to abort dragstrip runs because I awsnt able to physically move the lever into the next higher gear (it wouldnt go in). Also, when I drained the fluid, it was bronze with lots of sparkles in it.
Some friction needs to be present in there for the synchros to operate properly.
I got in touch with z_doc. He first told me that my master/slave cylinder were bad. I replaced them and bled them thoroughly, and the same issue existed. z_doc then told me I needed a rebuild (at a cost of thousands of dollars) or a new transmission. Well, when I put the gm factory fill 5w-30 (which is no longer available) back in there, all my problems disappeared.
I recently replaced the fluid with gm syncromesh and also had good results.
I do not agree with the suggestion on the bmw stuff.
***important note*** I am running the hurst short throw shifter - if that could make my situation a little different than the others.
Some friction needs to be present in there for the synchros to operate properly.
I got in touch with z_doc. He first told me that my master/slave cylinder were bad. I replaced them and bled them thoroughly, and the same issue existed. z_doc then told me I needed a rebuild (at a cost of thousands of dollars) or a new transmission. Well, when I put the gm factory fill 5w-30 (which is no longer available) back in there, all my problems disappeared.
I recently replaced the fluid with gm syncromesh and also had good results.
I do not agree with the suggestion on the bmw stuff.
***important note*** I am running the hurst short throw shifter - if that could make my situation a little different than the others.
Melting Slicks
Joined: Mar 2002
Posts: 3,108
Likes: 126
From: S.L.C. UT
I do not agree with zfdoc's recommendation on the bmw castrol oil. I used this stuff and constantly found I was grinding gears. It was like the stuff was too slippery for the synchros. In some cases, I had to abort dragstrip runs because I awsnt able to physically move the lever into the next higher gear (it wouldnt go in). Also, when I drained the fluid, it was bronze with lots of sparkles in it.
Some friction needs to be present in there for the synchros to operate properly.
I got in touch with z_doc. He first told me that my master/slave cylinder were bad. I replaced them and bled them thoroughly, and the same issue existed. z_doc then told me I needed a rebuild (at a cost of thousands of dollars) or a new transmission. Well, when I put the gm factory fill 5w-30 (which is no longer available) back in there, all my problems disappeared.
I recently replaced the fluid with gm syncromesh and also had good results.
I do not agree with the suggestion on the bmw stuff.
***important note*** I am running the hurst short throw shifter - if that could make my situation a little different than the others.
Some friction needs to be present in there for the synchros to operate properly.
I got in touch with z_doc. He first told me that my master/slave cylinder were bad. I replaced them and bled them thoroughly, and the same issue existed. z_doc then told me I needed a rebuild (at a cost of thousands of dollars) or a new transmission. Well, when I put the gm factory fill 5w-30 (which is no longer available) back in there, all my problems disappeared.
I recently replaced the fluid with gm syncromesh and also had good results.
I do not agree with the suggestion on the bmw stuff.
***important note*** I am running the hurst short throw shifter - if that could make my situation a little different than the others.
The BMW oil made my car shift like crap. I put the GM oil back in and it shifts perfect. But I would be real curious too see how that matched against royal purple and some of the other aftermarket oils.
Race Director
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From: Rolla Missouri
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I've been using Amsoil since 2005 and haven't had any issues.
http://www.amsoil.com/storefront/mtf.aspx
http://www.amsoil.com/storefront/mtf.aspx
