How Often to Drain and Refill AT's?

[supton]

Thermostat in or out of transmission? On mine I can push in a little button, then slide in a cotter pin (or nail or somesuch) to lock into full cooling.

Alternatively, does it have an antifreeze loop to the transmission? If that heat exchanger is external to the trans there ought to be lines which could be tapped to do fluid changes.

 

[DoubleWasp]

Originally Posted By: SteveSRT8
IME the Tstat in a trans never closes the cooling circuit off completely. I admit no experience here with larger Fords, but many Tstat equipped transmissions are easily exchanged...


It's a mixed bag of nuts how they do it in each one. With the Ford/ZF trans, it's a real mystery. Ford says it can't be done. Nobody has ever come forward with any information proving otherwise.

I've stuck to rigging a tube/bucket to feed new trans fluid directly to the filter inlet, and letting the old fluid fall out of the trans into a big drain pan.

 

[SteveSRT8]

^^^Well I'm about to find out. My RAM is fast coming up on 30k miles due to my lovely wife beating the carp out of it. Me and my local Trans Wizard will be servicing it. ZF 8 speed unit. Pan and filter are a single piece, so that's definitely on the table.

But I need to know how to exchange the fluid also...

 

[DoubleWasp]

Have the same thing.

After the recommendation in the other thread of getting the transmission hot before doing the exchange, I asked around and got more recommendations to do the same.

I just start worrying that with cold fluid being fed into the trans that it will stop flowing as much and start recycling the dirty fluid.

I suppose if one were to get the trans good and hot, the thermostat wouldn't see cold fluid until the very end, and even that fluid will be heated by the hot internals. Just wish I had a solid confirmation on that.

Were I to do a flush that way, then enters the problem of continuously feeding the trans it's fluid through the sorry fill plug inches from the flaming exhaust while this goes on.

Lot easier for the later 6R80 guys who get that nice little hole with the tiny dipstick toward the front of the trans.

 

[demarpaint]

Originally Posted By: DoubleWasp
Have the same thing.

After the recommendation in the other thread of getting the transmission hot before doing the exchange, I asked around and got more recommendations to do the same.

I just start worrying that with cold fluid being fed into the trans that it will stop flowing as much and start recycling the dirty fluid.

I suppose if one were to get the trans good and hot, the thermostat wouldn't see cold fluid until the very end, and even that fluid will be heated by the hot internals. Just wish I had a solid confirmation on that.

Were I to do a flush that way, then enters the problem of continuously feeding the trans it's fluid through the sorry fill plug inches from the flaming exhaust while this goes on.

Lot easier for the later 6R80 guys who get that nice little hole with the tiny dipstick toward the front of the trans.


I wonder if draining it hot, and filling it with a magnetic oil pan warmer plugged in, fastened however possible if the pan is non-ferrous would help eliminate the thermostat issue you're concerned with. Possible food for thought. They sure aren't making these transmissions easy to service.

I have a Wolverine oil pan warmer on my Jeep's transmission. If I had the same concerns I would plug it in before filling the transmission.

 

[meborder]

Originally Posted By: SteveSRT8
But I need to know how to exchange the fluid also...


Do this:

Originally Posted By: DoubleWasp
I've stuck to rigging a tube/bucket to feed new trans fluid directly to the filter inlet, and letting the old fluid fall out of the trans into a big drain pan.


or take it to a dealer that has a heated flush machine.

these are the ONLY two ways I know of to get a full exchange.

the 3x pan drop and refill is another viable option, but messy, time consuming, and does not get a full exchange either -- but is generally regarded as "good enough"