transmission fluid and cavitation

[dyoungen]

I have a 1985 Diesel Jetta with a 5 speed and no turbo. What seems to be the transmission fluid of choice? The tranny shifts ok but it sometimes hard to get into first. I"m not used to finding first gear and sometimes it seems to be in gear and sometimes it doesn't. Also it pops out of first once in a while.
Another thing I haven't seem mentioned in this forum, cavitation. I also have a 1987 Ford F250 with a 6.9 Diesel. One of the things we have to watch out for is cavitation in the engines, especially the 7.3. Does the VW Diesel ever have this problem?

[mystery3]

I like the redline mtl, they have some other weights as well.

As far as cavitation, do you mean in the water pump? Where does the cavitation occur in the fords?

[Vincent Waldon]

Cavitation refers to microbubbles that form in a fluid as a result of sonic pulses being transmitted thru the fluid.  The bubbles are highly erosive to metal.

In this case the issue is microbubbles in the coolant passages of diesel engines that have sleeved blocks... the normal "detonation" that is diesel combustion causes sonic pulses in the iron sleeves and cavitation eventually erodes the sleeves.

Ford solved the problem by specing coolant with special anti-cavitation additives for their sleeved diesel engines... Volkswagen solved the problem by not using sleeved blocks.   

[mystery3]

Thanks! I only knew of it in relation to props or pumps.

[dyoungen]

My 6.9 doesn't have sleeves. The 7.3 has thinner cylinder walls and that is supposed to be the reason they have a problem. Napa has "SCA"s to add to the coolant to stop the cavitation in the newer diesels. Just curious.

[Vincent Waldon]

Yeah, as I understand it it's the "thin walls", sleeved or otherwise, that allow the sonic pulses from diesel ignition to cause cavitation bubbles and the resulting metal erosion.

Some pictures of cylinder wall cavitation... for the geeks out there:

http://www.buyerzone.com/construction/rbic-diesel-engine-coolant.html
http://flashoffroad.com/Maintenance/Cooling_system/Antifreeze/antifreeze.htm

ASTM abstract with some info:

http://www.astm.org/JOURNALS/JAI/PAGES/JAI100686.htm

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[jb86]

this may help explain
VERY VERY IMPORTANT DIESEL ENGINE INFORMATION
i googled the product he uses.
only if it has cylinder sleeves.
jon