dizwiz24

The castrol stuff belongs in bmw engines, not our transmissions:

Ive had issues with castrol 10w-60 bmw stuff in my 93's ZF6.

I had shift-when-cold issues. More disturbingly, I had a lot of grinded shifts during WOT operation from 1 to 2 shift. I had to abort some dragstrip runs because the shifter would physically not move into the next gear at WOT.

ZFdoc recommended I replace my clutch hydraulics (following correct, careful bleed procedures) - which I did (with NOS parts) and it did not solve anything.

His next recommendation was a transmission rebuild at a cost of thousands of dollars.

The thing that fixed this was going to GM recommended tranny fluid. When I drained the Castrol 10w-60, lots of bronze speckles clouded the oil. That stuff was eating my synchros! I think GM now recommends syncromesh - which is the approved replacement for the unique 5w-30 transmission oil (note: this is not motor oil). The original trans oil p/n in my owners manual is not avail anymore.

Recently, I thought I had an improper throwout bearing (large OD for 89-93 black tag guide tubes) installed onto a small guide tube from a 94-96 transmission. I thought this might have caused my unusual results - where others seem to think the castrol stuff is great...However, when I took it apart, I saw that the throwout bearing was the correct one for the application. So that does not explain the bad results I had with castrol 10w-60.

Recently, Ive been using AMSOIL fluid and its worked great. I even changed it recently during a clutch swap. Hardly any bronze particles came out when I drained the fluid - so its working good.

GREGGPENN

I also observed notchy shifting when I tried the thicker TWS 10W-60 in my ZF a few years ago. When it was below 50-degrees, it would take about 10 minutes before I'd get "normal" shifting.

At the time, the original GM product (5W-30) was still available. Switching back to that fluid solve my cold weather issue. OTOH, I don't recall having problems getting it into reverse.

Because of my own experience...and observation over time, I think it's likely that many older black tag trannies don't do well on the thicker lube in colder weather. I haven't run a poll on it, but it's the best I could figure after running/participating in a couple of threads over the years.

Because blue-tags have different cut (angled) gears, I think they do well with either lube weight.

Bill's website (ZFDoc) simply states what ZF provided to him -- before they released rights of the ZF6 to another company. Since the mid-90's that information has not been updated to include possible modern synthetic options. Looking for ancillary feedback...possibly with lab testing is the best confirmation of whether a particilar product is adviseable to use.

That said, I believe AMSOIL has been proven reliable. Redline products seem a good choice as well. Mobil doesn't make anything suitable. I don't have an opinion on RP products...except to assume they're over-hyped. Or at least over-priced.

C66 Racing

Replied and sorry for the slow response, was offline this afternoon.

For those interested in the AMSOIL mentioned above, specifically designed for this type of application and being used by many forum members who all seem to share the above positive comments:
AMSOIL Synthetic Synchromesh Transmission Fluid (MTF) (Product Code MTFQT)

mxnuke

Not to jack this thread,but i just came from a bmw dealer and only sells the new tws 10w60 edge.he said he knew what i was doing with it [ zf6 trans ] and would not say it was safe to use.He said it was reformulated but did not have specs on it..So i put in a call to the only other bmw dealer in town and waiting on a call back..sucking the fun right out of this...lol

dizwiz24

return it.

dont take the risk.

youve read about a couple users here having issues with it.

use the amsoil stuff.

good luck in your decision

DMCCobra

I switched to Amsoil Synchromesh a couple hundred miles ago. The cold and warm shifting is much better.

Black89Z51

I'm using Amsoil Synchromesh in my ZF6. Great stuff.

pacat

I just picked up 2 quarts of Amsoil Synchromesh for the 6 speed and 2 quarts of Amsoil AGL for the rear end. I hope to do the fluid change this weekend. I will give you guys an update on the results.

DMCCobra

@pacat, I think you need a little over 2 quarts. I can't remember if it's 2.1 or 2.2 quarts.

GREGGPENN

2.2

pacat

Over the weekend I did the fluid change. Out with the old Castrol 10W60 and in with new Amsoil 5W30. After driving the car for about 25 miles I didn't think there was much improvement in the shifting, still a little stiff going into each gear and still very difficult getting into reverse when cold. Looking back thru all of the comments you guys posted on here I saw at least 3 of you suggest that the problem could be clutch related. Long story short, I replaced the Clutch master cylinder and problem solved. It’s now smooooooth shifting. Thanks very much everyone for all the help.

I also found this article on http://www.zfdoc.com/clutch_hydraulic.htm clearly stating, “Note: Difficulty getting into reverse when in this condition indicates that the clutch master cylinder is not at 100%.”

LEAK DOWN TEST OF THE CLUTCH
MASTER AND SLAVE HYDRAULIC CYLINDER
How to check out the operational condition of the hydraulic clutch system:1. Thoroughly bleed the system with Valvoline Dot3 Dot4 Full-Synthetic brake fluid.
2. Simulate the vehicle being parked on an incline for 12-24 hours with the front end at least 1 foot higher than the rear.
3. Lower the vehicle if raised for test. Note: Do not cycle (pump) the clutch before next step.
4. With the clutch pedal remaining depressed, start the vehicle.5. Try to put it into reverse when it first gets started (cold).
Note: Difficulty getting into reverse when in this condition indicates that the clutch master cylinder is not at 100%.
6. Repeat steps 1-5 of this procedure except with rear end raised.
Note: This will be the leak down test for the slave cylinder.