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can a trans cooler for a 740rs allison cooler be cleaned or is it best just to replace. i began to notice that after a drive i get some fluid spitting out of the dipstick

when i shut the truck off. i dont think its overfull. site glass shows full when cold and about half warm.

any tips on replacing the cooler/ the truck has a e7 300 engine.


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I assume that you presume the fluid is being restricted by a blockage? and you don't have a collapsed hose..

We have a trans cooler flushing machine at work that we bought from Allison, originally for 748 trans as the heat prior to us going over to Transynd cooked everything inside with the retarder working hard.

There were many occurances of trans fluid overheats, even boiling, but after we started to "reverse" flush the coolers on a trans change or shifting problems the issues subsided. The machine filter clogged up after just a few uses so we opened them up and they were full of small black carbon chips and small fibre pieces which our trans shop identified as clutch pack disks.

If we found a very large amount of metal in the input end we scrapped it, after sectioning a few of these we found the metal was well impregnated into the matrix and was obvious that it was restricting flow and would not clear with a back flush.

We figured an in-house cost of about $400 which included a new gasket... new at that time was $1200...

This is on Transit buses which probably have the same rough life as a municpal or trash truck. Our B400/500's still follow the same program but are larger than those installed on 74x series, and with the use of Transynd we have very few problems today.


BC Mack

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Transynd is the ticket for an allison for sure, we run 3000 series Allisons in School Buses here, have been since the MT643 was dropped, we change our internal filters every other oil change and we order the buses with an external spin on filter that gets changed every service, that has dramatically extended the life of the fluid and the life of the transmissions, the filter kit for a PTS3000 is a whole lot cheaper than a fluid change or a rebuild.

"Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin

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