Transmission or trans controller??

[MillTek]

Hi,
On our 1999 ML430 (135k miles) about two seeks ago, during the middle of a trip to the local store it refused to change gear into top (or overdrive - I'm not sure which). When we reached our destination I stopped the engine and restarted it. The car ran fine. Since then all has been great until this evening. The exact same thing happened. Refused to change into top gear so I stopped and re-started the engine. After that, all was well. I haven't changed the trans fluid yet.

Given that the problem went away when the engine was restarted I am wondering if it's the controller or the gearbox that's at fault. Any ideas anyone??

Also, could someone point me to a place where I can get good instruction on changing the fluid? I've searched the site but seem to come up mostly with discussions about whether the fluid should be changed or not.

Has anyone else had this exact same symptom??

Jim

[Kajtek1]

On the side IF to change the fluid, there is no easy answer HOW to change it.
I posted my procedure on 240,000 miles E class in this section under the "My take ..."
Took me 12 quarts and I could use more.
Other members are satisfy with dropping the pan and replacing the 3 quarts there.
With your present problem read the codes and check the fluid level.

[43sqd]

Get a scanner hooked up to the truck and read the codes. Just because the CEL isn't lit does not mean that there aren't any codes. There are many faults that can be stored that do not trigger the CEL.

[mickey.1430]

The trannies in the earlier MYs lacked a shield over the valve body which helped to prevent contamination of the small fluidic valves within the body. Contamination can result in erratic shifting and may be the problem in yours. See if any codes were recorded and try a fluid change.