12/11/04
STRANGE LIQUIDS:Transmission fluids
 

Transmission fluids seem fairly simple--manual transmissions ought to take gear lube, and automatics ATF. But neither is as simple as it looks. Most import stick shift transmissions take 90w, now ususally available as 80W90. One early exception is that most MG's, as well as other English cars and Volvos with the Laycock DeNormanville overdrives, use engine oil. 30W was the original specification, but 20W50 is OK in a pinch.  Some of the newer Japanese transaxles require ATF, even in the manuals. And ATF isn't quite as simple as it looks, either. Originally, General Motors transmissions used a fluid known as Dexron, and everything else used the Ford specification fluid. A common application for Ford ATF is the Borg-Warner transmissions used in many European and Japanese cars. There is a slight difference in viscosity; a oil company rep once told me that transmissions will operate on the wrong fluids, but that a GM transmission will shift rough with Ford fluid, and a Ford trans will be mushy on Dexron. Dexron has been reformulated twice, so what we get now is Dexron III, which contains additives which offer greater resistence to temperature degradation. I was told that the current formula contains rapeseed (also known as canola) oil, which is supposed to be as good at preventing the fluid from turning into a black gooey mess as the original whale-oil derivatives that were used in the original Dexron. There are also additives available (the major one is Lubegard) which also offer protection against heat damage to the transmission fluids.

Some years back, we started to see cars calling for a new Ford fluid, originally called FA6, now Mercon. It turned out to be Dexron, and so you often see Dexron labelled as Dexron/Mercon. The commonest supplier of automatic transmission now found in European cars is ZF, most of which use Dexron. In short, you cannot guess at what is supposed to be in your gearbox.

There are a couple of new fluids: Many VWs and Audis after 95 are listed as using a AT fluid that lube charts list as "AE", referencing Esso LT71141. We carry this as VW G052-162-A2, made by Pentosin in Germany, for $14.95/liter.
Some BMWs 95-99 are also listed as requiring AE fluid, but I have not been able to cross-reference the BMW number to the VW fluid. We have heard that later BMW's have sealed transmissions with a 100,000 mile factory fill, so don't do routine transmission service on these vehicles without BMW's advice.  Mercedes 96-later with the 5-speed auto trans are listed as using MBZ 001-989-21-03-10 which we carry for $12.50/liter.

Chrysler and some of the Japanese manufacturers use a highly friction modified fluid listed as ATF+3 or ATF+4, (AP3 and AP4 on lube charts). You can buy an additive that makes Dexron III meet this specification. There is also a new Ford requirement for Mercon V; again you can get additives to add to Dexron III for this.

Amsoil makes a universal synthetic transmission fluid that will work for Dexron, Ford, Mercon V and the ATF+3 and ATF+4 fluids. It claims superior high and low temperature performance, with three times the service life of petroleum fluids. We have this available at $9.95/qt.

Standard transmissions don't put a lot of stress on the trans fluid (except Mini's that run in the engine oil pan), but should be changed according to your owners' manual. Automatic fluids do run hotter and degrade eventually, but Dexron III is supposed to outlast the old Dexron II. Most factories recommend changes about every 25-30,000 miles.
 

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