Dear Forum-

I just want to say up front that I think the BMW Oil and the GM Oil are both fine... I'm probably insane and just wanted to explore something else:

Around two years ago I purchased my C4 and shortly after I pretty much went through the entire car and replaced all fluids and filters with the recommended choices. One of those fluid replacements was filling the ZF6 with Castrol TWS Motorsport 10w60.

I haven't had any real problems since, short of a hard 1-2 shift and some more than noticeable "notchy" behavior in my ZF6. Most of the 1-2 shift problem was linked to the well known hydraulic system problems with the clutch, so I've never completely blamed the transmission on that.

The nearest BMW dealer is about two hours away, and back in 2004, I purchased my Castrol 10w60 from Bavarian Motorsport online, which increased the overall cost per quart due to shipping.

So today, I went down to my local Royal Purple dealer and picked up three quarts of their Synchromax fluid for manual transmissions ($9/quart). I had read all the warnings and recommendations, but since I like to try new things (and I'm probably a fool) I went ahead and put two quarts and a half (give or take) into the ZF today.

I took it for a 30 minute drive and here are my impressions:

MUCH quieter than before, especially with the clutch out in neutral. The only real noise that remains is my aging throwout bearing... but the gear whine is (for the time being) negligible.

I also noticed, say, on the bypass, cruising at 75, that the car was much quieter. I used to think the electronic fuel pump was just extra noisy... but now I realize that it was gear whine. It's so quiet now, that now I can hear my throwout bearing going down the highway, which was obviously drowned out by gear whine previously.

Another observation was that the shift gate feels slightly less "notchy" going in and out of shifts. It still has that positive lock feeling as you enter a gear, but it just feels a bit smoother. This could be attributed to the fresh oil though, and may go away in the next week or so.

Since today was around 85 for a high, this is all based on warm oil temperatures... so cold shifting will have to wait until fall or later. Just looking at the weight of the oil; however, I would hope that this would be easier to shift in cold weather, over the Castrol 10w60.

I don't track this car, or really drive it extra hard at all, so I can't comment on attributes in that arena.

Since I'm only on day one, I can't say if this is going to cause any harm to my ZF over time, but I see an improvement (in my opinion) over the BMW dealer oil. Plus it was cheaper for my particular area.

Just thought I'd share and I'm just happy that it appears I have another option in my ZF lubricant. I'm not a certified technician, so don't consider this gospel by any means.

Have a great Holiday.

 

Thanks for the info Jim. I use redline myself and feel that there are other alternate options out there that are safe as well.

 

The "10W" in 10w60, means that it has the winter viscosity of a SAE 10weight oil.


Do you know what weight the royal purple is? It baffles me that this transmission needs some uber special lube.

 

CC - for some reason, the nature of the syncros in this box really put stresses on the sheering forces of the oil. It really has to withstand those pressures.

I am paraphrasing as a result of conversations with Bill B @ ZF Doc, so the message may not be as clear as he would give.

 

Royal Purple has a spec chart for the Synchromax on their website:

http://www.royalpurple.com/prodsa/scmax.html

Just looking at it I was guessing it was closer to a 5w at cold temperatures. Then again, my guessing skills aren't ANSI certified yet.

 

Mine are ISO9001 certified.

 

come back in a month and let us know. My BWM fluid felt notchy again after a month or 2.

 

thanks for the info.i have had good luck with amsoil's synchromesh as well.about 4k miles and all is well(except for the clutch but thats another matter).

 

I'll report back in a few weeks, enjoy the racing today!

I just heard Jim Nabors sing "Back Home Again in Indiana..."

I'm pumped!

 

This is kind of quick, not well thought out response, but it looks to me like you didn't use Royal Purple's recommendation for the ZF6 transmission????


http://www.royalpurple.com/techa/tranxref.html

The chart says Sae10w/30 or XPR5w30???

Frankly I think you might have made a mistake???

 

yea, that synchromesh stuff doesn't appear to be a direct replacement for C4 corvette, that specifies GM #1052931 (ZF-6), per that chart.

i don't care what anyone says, its either GM or the BMW oil, nothing else is getting near my tranny.