How do I clean out a used transmission?

I bought a used transmission and want to clean it out before installing it. Any one has any ideas of how to clean it? What type of cleaning fluid should I use or NOT use? Thanks Dave

I bought a used transmission and want to clean it out before installing it. Any one has any ideas of how to clean it? What type of cleaning fluid should I use or NOT use? Thanks Dave

I would drain the torque converter, and if the fluid is bad don't use the transmission....


the other issue is your transmission cooler and lines...must be cleaned when the replacement tranny is installed...

to do this the lines and cooler are flushed with water and reverse flushed ,then use dry air to purge out the water for 5 minutes...

If you have some nitrogen gas ...this would be best instead of air...

Remove the converter. Tip the transmission up on the tailstock and allow to drain overnight.

Drain the converter. This is tricky, like trying to get water out of a tire. You may be able to suck the fluid out using a thin plastic hose and a vacuum pump.

Remove the pan, allow it to drain. Clean out the pan and clean the pan magnet. If there is no magnet there, put one in (it's a round, 2inch dia. flat disc, about 1/16 inch thick, looks like a big washer)

Replace the filter and reinstall the pan. Virtually all the old fluid will be out of the transmission. But as noted above, if the fluid is dirty and the pan looks pretty muddy, there may be debris and problems inside which can only be corrected with a rebuild.

Thanks for the info! Would napa have pan magnet or would any magent do from home depot? Any tips on R&R the trans for the 1999 5.7 eng suburban? I am a back yard man so I was going to ues a new pump tank sprayer filled with trans fluid to flush line. Would that be good enough? Thanks Dave

Thanks for the info! Would napa have pan magnet or would any magent do from home depot? Any tips on R&R the trans for the 1999 5.7 eng suburban? I am a back yard man so I was going to ues a new pump tank sprayer filled with trans fluid to flush line. Would that be good enough? Thanks Dave
Yeah, that should be fine to flush the line; generally its just a case of moving the old fluid out, it's unlikely there is much actual debris deposits in there.

Auto pars places should have the magnet, but a hardware store might too. Any decent-size, strong metallic (not vinyl or plastic coated) magnet will do so long as its thin.

As for the re and re... is it a 4x4? If yes, it's probably best to remove the trans and transfer case together as one unit.
Otherwise, here are a couple of tips I wrote for an Aerostar owner a few months ago, but they probably apply here, too.
Welcome to AF.

Transmissions are heavy (100-200+ lbs with converter), depending on the model.
Obviously they can injure you if they fall off a jack, so keep your limbs out from underneath it when you pull it loose.

Place a piece of wood ( I use an approx. 12x18" piece of plywood) on top of the jack to protect the pan, or else you may dent it.
The most important thing is to place the jack at the balance point of the transmission, usually on the pan, usually a quarter of the way back. Some trial and error and great care will help here.

I have never strapped a trans down to the jsck because if the jack is off-balance, the trans will fall over anyways, whether its attached to the jack or not.

BTW you do have a nice big, wide floor jack right? A tiny floor jack is not up to the job.

Thanks to all.. I have a motorcycle jack and I will pull the 4x4 case and trans at the same time.. I will search the van site.. What type and brand of tran fuild shiould I use. I have no idea if I should use Synthetic or not.. Thanks again

Thanks to all.. I have a motorcycle jack and I will pull the 4x4 case and trans at the same time.. I will search the van site.. What type and brand of tran fuild shiould I use. I have no idea if I should use Synthetic or not.. Thanks again

use the lastest dexron VI or synthetic....GM stopped using dexron III because of too many warrantee repairs due to fluid failures...

this vehicle puts a good sized load constantly on the transmission and the use of a synthetic fluid in extremely cold or hot climates works best...