Overfilling an Automatic Transmission...how bad?

I read a lot of contradicting information online about the possible side-affects, if any, of overfilling an Automatic Tranny. Some say it's "no biggy", and some say it can cause MAJOR damage! Who is right?

I believe my 440-T4(4T60) is currently overfilled, and after reading about someone who has the exact same car having downshifting problems due to a shop overfilling his tranny, I am a little worried.

I understand that overfilling can cause the fluid to "foam", and therefore not lubricate as well, correct? Besides this, and the fact that it could cause fires from spilling over, is there anything else that is a possible symptom of putting in too much tranny fluid?

I have noticed that the hotter my engine, and therefore my tranny fluid, gets, the harder it shifts. It especially feels like it
"slips"/"falls" into 2nd gear when upshifting from 1st.

I checked the fluid HOT last Wednesday and noticed that the fluid went about 3-4 inches ABOVE the XXXXXXXXXXXX area. I am going to do a more thorough check of the level tonight, but I just wanted to know ahead of time just HOW big of a deal it is when it's deemed to be overfilled?

Take it to a Kwik Lube and ask them to check the fluid, and correct the level as needed. They can suck the excess out through the dipstick tube.

Rex in Fort Worth

i have and olds delta 88 with 4t60 my tranny is over full have not notice any problem. this transmission is noted for this problem your having your govenor is sticking causing over heating because it locking in two gears at the same time .now a cheap and dirty fix is to drain fluid. up front disconnect cooling line under raditator start engine and let it pump down just one min or so use common sense and judgement.at least so not showing on stick then put in tranny sealer and conditioner whole can slowly add trans-x or trans medic until your slightly above full it has to work in clutch packs.4t60 has a vaccume modulator you will notice lines in this area change all including recover canister all.also check park neutral switch if it is center so you can start in park and neutral if you can switch is ok trust me been their done that had the problem.i have several editorials on this tranny pages on this sit for more details on this subject.like i said i have a 91 delta88 4t60 and 91 chevy lumina 3.1 4t60-e both had this problem is ok. my cheap and dirty fix solve both cars.hope this helps.also blow out cooling tank with air hose it my have crud in tranny cooling system theirs a tank inside raditator. do not blow back into tranny.it my fix cooling problem.sounded like tranny fluid is thinning out when hot causeing a second problem.go from here lets see how you make out.

Post edited by: hobbist, at: 2008/03/27 21:37