Dexron VI and T-IV compatibility
 

1994 LEXUS SC400, 113K

Car has been running perfect until now. Needed to top off tranny fluid and went to O'reilly's for T-IV and the clerk brought about Dex6. Again, I told him I needed T-4 and he practically argued with me saying Dex6 is compatible and far superior. The bottle even says it can be used on my car. Out of nowhere, my car suddenly slipped and it seems ive lost OD. After researching, I see many say NEVER to mix different fluids. Is my tranny possibly ruined now? I keep finding conflicting responses about mixing the 2 and I need to know if they are compatible or not! Or, is it something else? Fluid is still clean (red) looking with no signs of debris. No burnt smell. No dummy lights. No signs of overheating. Immediately pulled over when lurching started and noticed a soft his from engine/tranny area. Couldn't hear it with hood down and hissing stopped when car cooled. Limped car home the next day, no hissing. HELP!

yeah mixing different types of atf is definitely not good. I don't know how long you drove on it, but I'd doubt your tranny is ruined.

Just get that dex6 out of there, that's what i'd do at least :D

not sure if the two types of ATF are compatible or not, but i'm sure a google search will help you out

wrong section, this is the LS section but we can help.
Toyota T-IV can only be bought at the dealership if I'm not mistaken, at least here in CA that's the case.

mixing is not good, but your trans is likely not compromised. how much did you put in?
getting it all out is going to be very difficult but I don't think you had to put in that much to top it off.

these trans are very sensitive to new fluid, even using the same T-IV, though it takes a lot to really make a difference (more than 4 quarts and depending on mileage/driving habit/maintenance interval, etc).

I topped off with just under a quart. I'm getting very conflicting answers on the addition of the new atf. Thought is was dex6 but it's Oreillys Global atf that says it's safe to use and compatible with T4. I put it in a month ago and only driven a few days a week, mostly highway. Have checked tranny fluid a couple times since addition and level was perfect. Now it's a tad over full when checked (of course, I am checking it after a good warm up and while car is on). Is there something else that will mimic tranny issues? No check engine light. Fluid looks great. No temp increases. No dummy lights at all but I seem to have lost overdrive. Again, it was running perfect and then jerked really hard and ibpulled it over immediately. Engine had revved up to about 4000-4500rpms and then settled at 3200-3500 at 60-65mph. After pulling over I kept it under 25. Drive it home the next day and there was a hesitation around 40-45, cruising speed. No symptoms at slower speeds. Does feel a bit sluggish but not much.