Cleaning the inside of a sludgy transmission/transfer case?

I recently picked up a used 5 speed and transfer case for my 87' 4x4. The shifters were sold separately by the seller so the top was open and i could see that there is a lot of sludge buildup and a bit of dirt that had fallen in from the levers being removed. I dont know any history about the transmission other than it came from a truck with about 120k miles on it. I was thinking about using the oil that's in it temporarily to both test the trans and clean it a bit before ordering the correct gear oil and changing it out. is there any additive i can put in with the oil to help loosen any deposits before i change the oil, i feel kinda weird putting some relatively expensive oil in such a sludgy transmission that i know has some dirt that fell in. by the way it shifts through all the gears and turns over by hand ok i think and the outside was coated in dry sludge from the engine with no wet spots near the output seals or anywhere so the transmission/transfer case itself has no leaks. also does anyone know of a shifter boot for the 4x4 lever? mines cracked and i cant seem to find any NOS ones anywhere. im wondering if any other cars use a boot that would fit or a universal one?

Tip - diesel fuel. I've been advocating it as an engine flush but I have seen posts on other forums recommending it as a LSD flush and would no doubt work as a manual transmission flush as well. I'd drain no more than a cup of oil out of it, top it up with diesel fuel and drive it for a day. No creative driving or highway miles, just a daily commute. It should be enough to work it's way through the synchros and bearings and break up sludge and any oil that has been overheated and laminated to gear surfaces and shafts. Take the sump off afterwards and use a spray can degreaser to wash it out as thoroughly as you can, cut a new sump gasket from cork by hand and fill it with the correct trans oil.

Thanks geezer! Will do that. I'll probably run it in 4 low so I can go through all the gears without speeding on my small back street I live on since its currently non licensed right now. Will the degreaser thin the new oil I put in?

If you only spray it up into the gear sets as best as you can, it'll run out and evaporate. I'd use a compressor and blow gun to try and blow the residue out from the bearings and synchros etc before closing up the gearbox and filling it. Be as thorough as you want to. Don't get busted by the po-po running it in the back street ;)

when i dropped the pan to spray the gears i noticed a piece of a bearing cage and some bits of metal...thats always a good sign lol. then i reached up and started moving the shift forks around and saw the upper stack of gears move forward and backward with it so that's probably not good either. syncros look fine though...i think? i split a quart of lucas oil stabilizer between the trans and transfer case and then topped them off with some sta-lube 85w-90 gl4. i drove it again and 1-4 seemed alright but 5th was still loud. i think im going to just run it and see what happens and if it fails ill just rebuild the other one. i see there is a rebuild kit for the KM-145 on ebay that comes with seals/gaskets/bearings/syncros it the bearings say made in japan on them so im assuming they must be decent? it costs about $150 US. does anyone know if this is a good kit or one to avoid or are there better options? here's a link https://www.ebay.com/itm/KM132-KM144...2215%7Ciid%3A1

Yeah...I'd probably stop driving it before it needs a trip to the dentist (y'know - lots of broken teeth) It looks like a decent overhaul kit in the ebay link.

Quote:

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Originally Posted by geezer101

.... cut a new sump gasket from cork by hand and fill it with the correct trans oil.

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This brings up a question. I took the pan off my trans, just to be more thorough in drainging out the oil. Do I need a new pan gasket now? (The old one came off in one piece.) If so, do I have to make one (part not available)?

Thanks
cj

The gasket is available (not sure if it's in a rebuild kit only...) and you don't necessarily need to make it from a cork sheet. Some guys don't even use a gasket - just RTV/silicon. I don't know if you'll need to replace your current gasket if it hasn't been damaged. I would do it just in the off chance it decides to leak.