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Poor Man's Flush vs Drain and Fill

xjsnake

NAXJA Forum User
Location
Nashville, TN
Ok first off, I have searched and didn't find anyone discussing what I'm about to ask.

Stock 97 XJ, 4.0, AW4, NP232, 135,000 Miles

I have overheated my transmission pulling a uhaul trailer moving after graduation (stupid I know) and I will be installing a transmission cooler that I picked up at a junkyard.

I have read threads on here and other forums about doing a "Poor Man's Flush" to change out close to all of the ATF in the system.

I have also read about doing a "Drain and Fill"

I am reasonably certain that the fluids (ATF, Gear Oil, Brake Fluid, Power Steering Fluid) have never been changed...

Regardless of the method that I choose to do, I will be dropping the pan and changing the filter (screen) in the transmission post haste.

I was listening to The Car Show on the radio (yes some young people do listen to AM stations...) and they strongly recommend against changing more than about 30% of the ATF at any one time because the detergents in the ATF can clean too much gunk out and cause problems if the fluids are changed all at once.


My questions are: Would doing a "Poor Man's Flush" cause too much cleaning to occur in the transmission and send gunk flowing through my newly upgraded system? Or should I do a succession of "Drain and Fill's to slowly change the fluid over to prevent releasing too much gunk into my transmission? I do know that I have read numerous threads discussing over-cleaning by using synthetic motor oils. Would this be a similar concept to what would be occurring in my transmission?

All feedback would be greatly appreciated and thanks in advance...
 
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IMO, there is no problem with flushing all the fluid at one time. The problem is doing a "power flush" at any one of the oil changer places that may force debris through the tranny.

My favorite method of the poor mans flush is the following. IMO it is much better than doing a pan drain and fill which doesn't get all the old fluid out:
a) Go to the hardware store and get a brass barbed connector 3/8" male-to-male and also 2 hose clamps.
b) Cut one of the tranny soft lines near the radiator; leave enough space to put the brass connector back in and attach the clamps.
c) Figure out which is the "out" side and which is the "return" side. The return goes to the back of the tranny, the "out" comes from the front.
d) Put the "out" line pointing into a 5-gallon bucket. Have a friend start the vehicle.
e) Drain about 0.75 gallons into the bucket, the system will run dry. Tell the friend to turn off the XJ. Refill the tranny with 0.75 gallons (or close to the same amount you pumped out).
f) Repeat step 'e)' 2-3 times until the fluid coming out turns from dark to clear red.
g) Use the barbed connector and hose clamps to repair the cut in the transmission hose.
h) Top off the system when it is idling in Neutral. You are now full with fresh fluid.

Total time is 10 minutes or less. I have 150k and do this once a year and the tranny runs great.
 
If you are concerned about a 100% fluid change, just change the filter and then use the drain plug on the trans pan. Once every 150-300 miles, drain the pan and add fresh fluid. After 4-5 cycles, the drained fluid should be almost as clean as the new fluid and you can stop.

I drain the pan once a year at the same time the differentials get drained and re-filled.
 
IMO, there is no problem with flushing all the fluid at one time. The problem is doing a "power flush" at any one of the oil changer places that may force debris through the tranny.

My favorite method of the poor mans flush is the following. IMO it is much better than doing a pan drain and fill which doesn't get all the old fluid out:
a) Go to the hardware store and get a brass barbed connector 3/8" male-to-male and also 2 hose clamps.
b) Cut one of the tranny soft lines near the radiator; leave enough space to put the brass connector back in and attach the clamps.
c) Figure out which is the "out" side and which is the "return" side. The return goes to the back of the tranny, the "out" comes from the front.
d) Put the "out" line pointing into a 5-gallon bucket. Have a friend start the vehicle.
e) Drain about 0.75 gallons into the bucket, the system will run dry. Tell the friend to turn off the XJ. Refill the tranny with 0.75 gallons (or close to the same amount you pumped out).
f) Repeat step 'e)' 2-3 times until the fluid coming out turns from dark to clear red.
g) Use the barbed connector and hose clamps to repair the cut in the transmission hose.
h) Top off the system when it is idling in Neutral. You are now full with fresh fluid.

Total time is 10 minutes or less. I have 150k and do this once a year and the tranny runs great.

Yarp, that's pretty much what I did after overheating my tranny last summer. I have a tranny cooler installed so it is simple to remove the return line and dump 2 qts at a time. Otherwise, that is a good process.
 
IMO, there is no problem with flushing all the fluid at one time. The problem is doing a "power flush" at any one of the oil changer places that may force debris through the tranny.

My favorite method of the poor mans flush is the following. IMO it is much better than doing a pan drain and fill which doesn't get all the old fluid out:
a) Go to the hardware store and get a brass barbed connector 3/8" male-to-male and also 2 hose clamps.
b) Cut one of the tranny soft lines near the radiator; leave enough space to put the brass connector back in and attach the clamps.
c) Figure out which is the "out" side and which is the "return" side. The return goes to the back of the tranny, the "out" comes from the front.
d) Put the "out" line pointing into a 5-gallon bucket. Have a friend start the vehicle.
e) Drain about 0.75 gallons into the bucket, the system will run dry. Tell the friend to turn off the XJ. Refill the tranny with 0.75 gallons (or close to the same amount you pumped out).
f) Repeat step 'e)' 2-3 times until the fluid coming out turns from dark to clear red.
g) Use the barbed connector and hose clamps to repair the cut in the transmission hose.
h) Top off the system when it is idling in Neutral. You are now full with fresh fluid.

Total time is 10 minutes or less. I have 150k and do this once a year and the tranny runs great.

I recomend this over the drain and re-fill method as well. And don't finish untill your done with the cooler install as these tranny's need one in order to last.

I found a giant steel row unit in a chevy astro van at the junkyard.
IMG_4817.jpg
 
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