Hi, does anyone know if it's OK to overfill your transmission? I just got a transmission flush w/ a filter change and my fluid is now about 1/8 inch above the full mark. I went back to the transmission shop and I asked them to suck out a little and they told me that it won't hurt anything to have too much fluid and if I filled it way too much there's a vent so it's not a problem. Is this true? I have the 4r70w tranny.
BTW, I just had this done w/ 62,000 miles on AMSOIL ATF which I had flushed into my tranny at 6,000 miles. when the guy took off the pan he looked shocked and went to show the other guys in the shop. I thought maybe something looked really bad until he showed me the pan. The magnet was completely clean. I'm guessing there's usually a bunch of metal shavings on it considering how shocked the guy was. AMSOIL must be some pretty good stuff.

 

i hav the same tranny in my truck.i did a filter chang at 60k on mine w/ regular mercon 5 oil and the pan was a little grey, but nothing severe.i have seen a little overfull like you described and it probably will not hurt anything. but dont let that fool you.if anything on the engine or trans is to overfull which would be a quarter of an inch or more could possible do damage to either the engine or trans.the vent on the trans is not to purge excess fluid but to allow the trans to vent vapors as theoil heats up during use.

 

I've run the same tranny, the AOD, the AODE, the C3, the C4, the A4LD, the TH400 and the 700R4 with fluid up to 1/4" above the "full" mark on the stick with no trouble at all.