I have a question about changing the transmission fluid and filter in my 2001 Jeep TJ with the auto transmission. I plan is to remove the return line from the transmission cooler, and start the jeep and let the transmission pump its fluid out. My questions is, if I do this until no more fluid comes out, then turn the jeep off immediately, will this harm the transmission? I would then drop the pan, change the filter, re-install the pan and fill, then run and add fluid as necessary to reach the proper amount. Is my plan good or will I muck something up?

I would get a service manual and follow the procedure,... I wouldn't want to run the transmission dry.

TMoney2007 said:

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I would get a service manual and follow the procedure,... I wouldn't want to run the transmission dry.

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TMoney, I have thought about that, but as soon as the flow starts to slow down, I would shut the engine off which would stop the pump. A new transmission will be dry until they put fluid in it and run it to circulate and get to the correct fill amount.

I have thought about just draining about a gallon out, and when added to the gallon that is lost from dropping the pan, I would be changing out two of the three or so gallons that they system takes. The fluid is pretty brown, probably what came in it when produced, so I would like to get the most out and replace with new.

clarythedrill said:

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TMoney2007 said:

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I would get a service manual and follow the procedure,... I wouldn't want to run the transmission dry.

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TMoney, I have thought about that, but as soon as the flow starts to slow down, I would shut the engine off which would stop the pump. A new transmission will be dry until they put fluid in it and run it to circulate and get to the correct fill amount.

I have thought about just draining about a gallon out, and when added to the gallon that is lost from dropping the pan, I would be changing out two of the three or so gallons that they system takes. The fluid is pretty brown, probably what came in it when produced, so I would like to get the most out and replace with new.

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Waiting until the fluid slows down means that you're waiting until the fluid isn't pumping anymore... which is running it dry.

Saying you're going to turn it off as soon as it is running so dry that no fluid is flowing doesn't change the fact that you're running it dry. I wouldn't do that.

Drop the pan and refill more than once. Go get a fluid flush from a shop that uses a machine that doesn't overpressurize the system...

I wouldn't do what you are thinking of. I would use the procedure from a service manual instead.

New transmissions aren't run dry, they're filled with fluid and then topped off. They don't start them empty and then add fluid to them.

Definitely don't run it dry, I typically have 5 qts in trans and at least another qt in the torque converter before running it.

Drop the pan and replace filter.

silverado_lover said:

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Definitely don't run it dry, I typically have 5 qts in trans and at least another qt in the torque converter before running it.

Drop the pan and replace filter.

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Don't flush it either. Just drain, refill, drive around for a couple hundred miles, then drain & refill again.

Tracking all. The system holds 8 quarts for dry fill. I want to try to get as much new fluid in as possible. I could do the drop pan and refill a second time after driving some, but that would still result in a mix of the old really brown fluid with the new stuff. Seriously, this fluid is brown like motor oil, not a hint of red in it. The thing shifts smooth as silk, surprisingly.

Corps_Ag12 said:

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silverado_lover said:

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Definitely don't run it dry, I typically have 5 qts in trans and at least another qt in the torque converter before running it.

Drop the pan and replace filter.

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Don't flush it either. Just drain, refill, drive around for a couple hundred miles, then drain & refill again.

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The flush machine saw just connected in line with a transmission fluid line and cycled in new fluid using the pressure from the pump in the transmission as the old fluid came out. I don't know how other flush machines work, but that one never did any harm. My dad used it on tons of vehicles for years and never had a problem.

TMoney2007 said:

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Corps_Ag12 said:

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silverado_lover said:

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Definitely don't run it dry, I typically have 5 qts in trans and at least another qt in the torque converter before running it.

Drop the pan and replace filter.

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Don't flush it either. Just drain, refill, drive around for a couple hundred miles, then drain & refill again.

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The flush machine saw just connected in line with a transmission fluid line and cycled in new fluid using the pressure from the pump in the transmission as the old fluid came out. I don't know how other flush machines work, but that one never did any harm. My dad used it on tons of vehicles for years and never had a problem.

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I am going to remove both lines from the cooler, and let all drain out that will drain out, then reconnect. I will then change out the filter and refill. Hopefully that will get about 5 quarts of the new fluid in the system. I may buy one of those pumps from the parts store to cycle in the the left over new fluid, through the fill tube, after a couple of days of driving. After this and new brake fluid flush tomorrow, this vehicle will be baselined with all new fluids everywhere, since I do not know the service history from the previous owner/owners.

clarythedrill said:

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Tracking all. The system holds 8 quarts for dry fill. I want to try to get as much new fluid in as possible. I could do the drop pan and refill a second time after driving some, but that would still result in a mix of the old really brown fluid with the new stuff. Seriously, this fluid is brown like motor oil, not a hint of red in it. The thing shifts smooth as silk, surprisingly.

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If it ain't broke, don't fix it

clarythedrill said:

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Tracking all. The system holds 8 quarts for dry fill. I want to try to get as much new fluid in as possible. I could do the drop pan and refill a second time after driving some, but that would still result in a mix of the old really brown fluid with the new stuff. Seriously, this fluid is brown like motor oil, not a hint of red in it. The thing shifts smooth as silk, surprisingly.

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Motor oil and transmission oil are two different beasts seeing two different services. One can see gasoline explosions and solid particles vs. oil seeing metal rubbing on metal and heat. But the extreme heat changes is what causes things to go south faster on motor oil than trans fluid.

The best measure (besides sending it off to the lab) is to smell it. If it smells burned, then it would be best to change out completely. If it is just brown vs. no red but smells like good oil, then just change what you can and get on with life.

Unless you're pulling 100klb loads going up 15% inclines every day, you should be fine. Technology has improved from the 50's, 70's, 90's and 00's with fluids and chemistry.

~egon

So I pulled the hoses from the cooler and let them drain, then dropped the pan and changed out the filter and cleaned off the magnet. Put it all back together and it took exactly one gallon of fluid to get to the proper level after a good ride to get it up to temp and circulating. I have a hand pump that I will use to pull another gallon out after a week or so of driving, and replace with another new gallon of fluid. That should last it for a good long while and end up with mostly new fluid.