Old Mercon V Fluid??

[Marauderjack]

As our trans fluid ages what exactly happens to it besides burning??:confused:

The reason I ask is my trans was "Freewheeling" lately and by freewheeling I mean when coasting down to go around a curve it would feel as if it was in neutral for a second when I got back on the gas.....kind of like the pump had to build pressure...if that makes sense??:cool:

It only happened at about 35 MPH at one certain curve on my way home and most people wouldn't even notice it!!:shake:

I drained the trans pan (a little less than 4 quarts) and put new Mercon V in and....VOILA....no more freewheeling??:beer:

Just wondering if the fluid viscosity breaks down over time?? BTW, what I drained was almost as clean as new and had no burned odor at all!!:beer:

Also, all up shifts were firm and crisp....it was just the down shift on that one curve that felt funny!!:rolleyes:

Marauderjack:burnout:

[RF Overlord]

jack, I don't have an answer for your apparent "freewheeling" condition. The only ways I know of for a transmission to slip into neutral are either an internal problem or if the fluid level is so low the pickup becomes uncovered. Incidentally, that's why Ford put that little "well" in the middle of the pan; older versions of this transmission had that very problem.

Anyway, ATF isn't subject to the same conditions as motor oil, which is one reason it doesn't require changing as often. There are no combustion by-products to deal with, no fuel-dilution issue, no condensation, and it's a closed system so outside contaminants aren't introduced. ATF will, however, oxidise if overheated too much or too often, and the additive package gets depleted over time, just from normal use. Like motor oil, you can't judge the fluid's condition solely by its appearance. This is why periodic changing is needed. Exactly how often is dependent on driving style & conditions and the power level of the engine, among other things. It can be as little as 10,000 miles or as much as 30,000. .

[Marauderjack]

I think it may have to do with viscosity since 4 quarts of new stuff not only cured the freewheeling in the curve but also a long delay when turning the O/D OFF when coasting.....2-5 seconds for the down shift (especially when HOT)!!:argue:

Now it down shifts like new.....about a second or less after turning the O/D OFF!!:beer:

I am changing the oil in about 1000 more miles and will do the trans again then!!:cool:

I would expect the viscosity to change in time and hopefully that is it!!??:beer:

Marauderjack:burnout: