How to get all trans fluid out of a 4L85E to change to Synthetic fluid?

[ChinaUK]

Hi everyone!

This is my second post on this AWESOME forum! I'm finding it full of extremely helpful information.

My wife and I are proud new owners of an 04 Trek 28rb with 8.1 motor and 4L85E tranny on a P32 WH chassis.

I want to change the transmission fluid to synthetic, but other than the 5 quarts that are in the pan, which I'll remove, how do you get the rest of the fluid out so I can do a full fluid replacement on this tranny?

I did some searching but only found information on the Alison transmission on this subject.

Any help would be greatly appreciated!

[ChinaUK]

Hi everyone!

This is my second post on this AWESOME forum! I'm finding it full of extremely helpful information.

My wife and I are proud new owners of an 04 Trek 28rb with 8.1 motor and 4L85E tranny on a P32 WH chassis.

I want to change the transmission fluid to synthetic, but other than the 5 quarts that are in the pan, which I'll remove, how do you get the rest of the fluid out so I can do a full fluid replacement on this tranny?

I did some searching but only found information on the Alison transmission on this subject.

Any help would be greatly appreciated!

[M&EM]

If I were doing it, I would consider draining and droping the pan, replacing the filter, reinstall the pan and adding new oil equal to the drained oil. Then I would take it to a quick lube type place and have them do a power flush of the transmission.

[edgray]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">This is my second post on this AWESOME forum! I'm finding it full of extremely helpful information. </div></BLOCKQUOTE>
WELCOME to iRV2.com from your statement, I can tell you are going to be another great asset to our forum. We all learn from each other here, so feel free to post any questions or answers you may have.

When you drain out the original fluid, be sure to measure VERY CAREFULLY how much you remove. Replace with the same amount of synthetic. Go for a short drive to fully warm up the tranny. Then REPEAT the process of draining and replacing with synthetic, again. This is one of the two methods that Allison considers adequate to accomplish the conversion to 100%synthetic, so it should be good enough for your GM tranny also. IF there is an external spin on filter, like on the Allison, I suggest you change IT when you do the SECOND drain. ED

[Art D]

My 4L85E looks like it has a drain plug on the torque converter in addition to the pan. Does yours?

[CJBROWN]

I've done a lot of trans service on various rigs, and converting to synthetic (the new Allison has Trans-syd or whatever).
Ed's advice is recommended over a flush machine if you can't pump out the torque converter.

On older ATF's you could disconnect the outline cooling line and pump out the converter. I've done a lot of them that way. In any case, you do need to drop the pan and clean off the magnet and replace the filter (before the spin-on style of late)

I've used a drain plug in the TC in a Ford behind a V-10. Definetely shifted better with synthetic ATF, they run cooler, and is very much worth the effort.

[ChinaUK]

Thanks for all your imput guys!

I had heard of the disconect the line and pump it out method but did not know if it was safe or not on this trans. I also may go with the "drain it twice" method, the first time will be a total removal cleanout and reinstall etc. I most likley will not change the filter as my coach has only 1600 miles on it, so would there be a need at this early point in my tranny's life to change the filter?

I will also be welding in a bung so I can mount a temp sender. The gauge is already installed.

ArtD, you say your saw a drain plug on the converter? I have not looked around the bell houseing to see if it has an opening to get to the TC, does yours ahve this? If so, what year is yours? Mike is a 2003 P32 built in late 2002.

Has anyone tried the disconect the return line at say the cooling radiator and pump it out while adding the new fluid down the dipstick so it does not suck air?