flushing tranny cooler

[Coalman]

Well I am getting my allison auto rebuilt and wanted to know the best way to flush the tranny cooler and radator out . I am going to go with dextron 3 instead of the motor oil . Also is there something beter than dextron 3 or is that going to be ok Thanks Kevin

 

[glcaines]

Dexron III is what the 1545 Allison in an A3 was designed to take. Don't use any other Dexrons as the newer Dexron's are not compatible with the Allison's seals. You can also use Castrol TranSynd, which is an excellent fluid, but very expensive. I would go with the Dexron III. It is very difficult to get all of the motor oil out of the transmission, cooler and torque converter. Using the repetitive drain and flush method works best in my opinion. Perhaps you can get some cheap Dexron III compatible fluid from NAPA in a 5-gallon pail and change out the fluid before you pull your old transmission. Then you are all set for the Dexron III in the new transmission. There are a lot of posts on SS about the drain and fill method of switching from MO.

 

[Coalman]

The tranny is already out, all I have is the cooler radiator and lines that need flushed. I was thinking of blowing it out with air first . The guy doing the tranny said use mineral spirits to flush it out. I am going to try and rig a pump up and just pump it through the lines and cooler if that works I will pump some dextron 3 thought also.The tranny will be rebuilt and all clean and ready to put the dextron 3 in when I get it back

 

[shovelheadmike]

That is what they normally do. Blow it out with air, then pump a bunch of new clean trans fluid through lines and cooler.

 

[glcaines]

Yes, if it's out all you can do is really blow it out and then flush it. After your rebuilt transmission is back in, I would recommend a drain and flush because Dexron III and TranSynd are not compatible with motor oil and you want to get all of it out.