It's all about heat...

These transmissions have no lockup... so, LOTS of heat. If heavy loads are used, like towing, or lots of steep grades, I would change it sooner than later.

If no heavy loads, or steep grades, normal driving, long intervals would be fine.

If there is a detected slip, filters need changing ASAP. Friction material can rob pressure from the system creating more friction material and added heat.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Mine does have a spin-on filter, but it is an aftermarket add-on.

Dkr.

I am curious how hot these 722.3 and 722.4 transmissions get with only the stock radiator tank heat exchanger. That should play a huge part in the fluid breaking down sooner. In my 87 300td, the stock 722.3 felt like it had a very "slushy" torque converter. I was poking around under the hood after driving it in the summer and touched the trans cooler line which goes above the radiator and i swear there must have been lava running through it. I have a 722.6 in it now but am still only running the stock cooler. On a hot day driving pretty easy, I have seen up to 110c on the 722.6 (i can watch it on my trans controller). Even once cruising on the highway with torque converter locked on a hot day it will have a hard time cooling down in to the 95c range. The stock heat exchanger is not adequate in Texas heat at all.

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83 300CD- sanden, dual p/f condensers, 160a alternator, ect
91 300TD- 722.6, #22 head, 3.5L IP, w140 manifolds, ect

I think all transmissions benefit from installing an auxiliary cooler. Some people claim you can over-cool the fluid, but all charts I have seen suggest the cooler the better except Alaska winters. But, most production cars rely solely on the in-radiator heat exchanger. Our 2002 T&C minivan has the factory towing package, which added a power-steering cooler and oil cooler, but no aux tranny cooler, which seems strange. In my 1960's classics, I chose to use solely an aux tranny cooler, without plumbing it also thru the radiator. That is because a coolant leak into the tranny fluid will quickly destroy the tranny. Adding one to my 300D's would be challenging because there appears to be no room to run tubes thru to the front of the radiator.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans