Its that time again ...

ATF+4 is synthetic and recommended to replace ATF+3. Both vehicles can use either ATF.

Per Chrysler's TSB on ATF usage I found this note:

NOTE :ATF+4(R) IS COMPATIBLE WITH ATF+3 AND CAN BE USED TO TOP OFF VEHICLES THAT CURRENTLY HAVE ATF+2 OR ATF+3.

So yes, the two fluids can be mixed. It would be far better if you had a flush done to change all the fluid to ATF+4 as well as a pan drop but it's not required to do so. Pan drops normally only change 1/2 or less of the total fluid depending on vehicle.

Thank you for the information.

My dealer told me its fine to run it in my 96 trans which uses +3.

But they said once you go to using +4 don't put +3 in it anymore..

The TSB:

Thanks for the TSB, but I do not see the Dodge Stealth on this list.

Does anyone know if I can use ATF+4 in a 1991 Mitsubishi 3000GT (Same as the Stealth). The Stealth/3000GT uses a Chrysler designed automatic transmission and I have previously used Molar ATF+3 when I drained (yes, it actually has two drain plugs, one for the drive axle and the other in the trans pan) and dropped the pan.

Bob

ATF+4 can be used on any car that is specified for ATF+3. The opposite is not true.