Would this work?

[Matt_S]

I want to do a complete transmission fluid change as my car approaches 100k miles (89k currently). I wouldn't even consider it without a pan drop/filter change first, though, so here's the plan.

- Pan drop/filter change. Refill with 7.4 qts ATF, as per the manual.
- Immediately disconnect Magnefine filter, start car, run 1/2 gallon through, refill with 1/2 gallon, repeat until fluid runs clean and clear.

I don't want to use more fluid than is really necessary, as I'm not planning to use a cheap fluid. The theory here is that the clean fluid in the pan will displace the dirty fluid in the trans and torque converter before finally going through the cooler, which I understand is the last stop along the fluid route before it goes through the final drive and back into the pan. The end result will be 95%+ new fluid. This is a 2000 Monte Carlo with a 4T65E trans.

The only concern is that the final drive will be dry while I'm doing this, but since the car will be in Park, that shouldn't be an issue.

Am I correct in my thinking? Any red flags?

 

[Gary Allan]

Looks good to me ..the only thing that might be a problem is that some transmissions don't route to the cooler in Park. Neutral usually works for these. I don't know your automatic.

I wouldn't worry about the "dry" deal. You don't have to run the pan dry before stopping and adding more fluid. Just drain xxx ..stop ..add...etc. Just stay in the range of the sump. Over fill it intially. No gear train movement will occur so you won't aerate the fluid. The only thing moving is the converter and its internal turbine connected to the pump shaft.

Good luck!

 

[Matt_S]

Good, thanks. I thought I was fine, I just wanted to hear it from someone else. I only plan on pumping 2 qts at a time, the pan capacity is 7.4, so I'm not worried about that, but my understanding is that the fluid gets routed through the cooler, then to the final drive gears. They would be dry during the flush. I'm not too worried about that, though, since the car will be in Park. The trans does route fluid through the cooler at all times, too. I discovered that when installing my Magnefine (had the wife start the car with me pointing the line at the drain pan to verify flow direction).

 

[T-Keith]

Why not just change the fluid, let idle, then change it again? This would get 90% of the fluid out and nearly all of the contaminants.

-T

 

[FazerZ]

Your proposed plan sounds good. Getting the old fluid out of the convertor and the cooler is a good idea and will allow for a more complete fluid change.

On the 4T65E, the torque convertor is charged in park and there is cooler flow, so the park range would be a good idea.

Some Dodges/Chryslers (and its close imported cousin Mitsubishi) automatics only charge the convertor and have cooler flow in neutral or a driven range. It's silly and a pretty bad idea, but thats another topic. Some later model Fords have a thermostatically controlled cooler flow valve, so you have get the vehicle up to operating temperature, before getting any cooler flow.

However, in park, the geartrain in this specific transaxle is turning. There is a lot of movement in this transaxle in park. The only time the geartrain is heard stationary is in a driven range with the wheels stopped. For example, in the overdrive range, sitting at a stop, the only parts moving would be the main pump and convertor pump.

Just make sure you have the correct cooler line so not to make a mess!

Two successive drain/fills would not be as effective in getting the old fluid out. More a method of dilution, but still worthwhile if cooler lines/convertor drain plugs are inaccessible.

What ATF are you planning to use?

DH

 

[Ken2]

1) I'd clean the transmission with Auto-Rx first.
2) Don't trust the manual for quantites. Check the dipstick as you go.
3) Don't try to save costs too much...have a quart or two of extra ATF in case it doesn't flush clean with what you think it'll take or if you drain out more than you plan to.
4) Install a new Magnefine filter.


Ken