Borg Warner Velvet Drive Tranny Fluid Color

About a year ago after moving our Defever 44 to Annapolis from Florida after purchase, I changed out the ATF. The fluid from one transmission was dark brown. The other was still bright red. I just changed the ATF again, 30 hours on the clock. Same result. Dark reddish brown from the same one, the other bright red. Should I be concerned about the transmission that is turning the ATF brown? Cause?

catalinajack said:

Should I be concerned about the transmission that is turning the ATF brown? Cause?

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Yes.

Clutches slipping perhaps.

What Capt. Bill said.

Also perhaps a bit of raw water from the transmission fluid's heat exchanger seeping into the ATF might be the cause.

If you smell the fluid on the dipstick, does it smell "burned." I know, how do you define that smell? But I think most people would recognize a burned smell, particularly if you compare it to the smell of the "red" ATF. If it does smells burned, then Capt. Bill's suggestion is more in line with reality than a raw water leak.

ATF turns dark with time and use, even if everything is okay with the transmission. It should be changed as soon as it starts doing this, or preferably before. But if the fluid you have now was put into both transmissions at the same time and one is still red and the other one is now dark, then there is a problem of some sort causing this.

catalinajack said:

Should I be concerned about the transmission that is turning the ATF brown? Cause?

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If the fluid is "milky" I would suspect water intrusion.
If the fluid is clear but brown I would suspect heat.
That's not a lot of hrs for a significant color change...

My opinion most likely heat related... and a perfect case where a Non-Contact Infrared Thermometer With Laser Targeting can be a great tool for troubleshooting. The cheap ones may not give you the exact temp but you are looking for large differences not couple of deg. Take it out for a run and check them both after running at cruising speed for awhile.

Fluid change on a BW leaves a good bit undrained. Old fluid hides in reduction housing and cooler and lines.

Do a couple more changes with a run between each.

A sample can tell you if it is water. Or put some in a spoon and hold over a lighter. Spatters, there's water.

A trace of water can corrode iron parts and turn fluid brown, not always milky.

What does the dark fluid smell like?

Many thanks for the advice so far. Smell? Unfortunately, I discarded the fluid. I am going to start with a trial run over the weekend to determine whether the "bad" transmission is running hot. Easy test. If not running hot, I will move on to the other possible causes. If running hot, I will change out the cooler. The boat came with five brand new spares. I will post the results.

Bacchus, I thought as you did that 30 hours was surprisingly short for brown fluid even if the discs were slipping especially because I experienced no operational anomalies in 1,200 miles of cruising.

Ski, I will check for water intrusion (teaspoon method) and my run this weekend if the temp test shows normal. If water is present, I will change out the cooler as I believe this would be the likely source. However, it may take may than a couple of hours of run time to get an indication of water. I may have to run the boat until the fluid turns brown again and send a sample out for testing. Silly me, I should have retained some for a test.

Around those parts Eastern Canada most use no 30 non detergent oil in bw trannys 2-1 2.57 -1 2.9 -1 with good results.Softer shifts and prolonged oil changes.Thats for diesels under 3000 rpm.If you have heat problem or slipping cluthes thats different story.Hope you track down down your problem.Good luck.

If the fluid is burnt I highly doubt it's due to the cooler. Don't you have a high temp. alarm on your transmission?