The Stovebolt Site Forums The Shop Area Driveline Need a little advice

I recently bought a SM420 trans out of a 54 1/2 ton. The trans passes the bench test for shifting, the gear oil was black but no water in it. Sounds quiet spinning it at 600 rpm no load in all gears. Before I pop the covers to take a look see, I was planning on dropping the old oil and refilling with ATF and run it with a 1/2 drill motor on its snout to clean the gears and case. Can anyone see why I shouldn't do this? ATF has detergents and I think it will give it a good cleaning this way. If everything looks good, I'll probably run it without the rebuild.I should say after it has cleaned, I will replace with GL1 90 weight
Thanks in advance,
Steve

The folks here don't suggest ATF fluid. They suggest regular old 90 weight oil. Same thing you'd put in your differential.

Not even for a cleaning then replace with GL1 90 weight?

If you want a thinner "solvent", try diesel/kerosene sloshed around; then, drain and rotate/"rinse" a few times with gear oil?
(I'll probably get booed on offering this suggestion.)

Diesel fuel is cheap, it's a good solvent, and it's got enough of an oil base that it won't promote rust by getting things too clean. Pour about a gallon in, spin the trans for a few minutes with your drill motor, and let it drain overnight. Refill with 90 weight mineral oil (not hypoid lube) and drive on
Jerry

That is what I will do. Thanks Jerry, Tim and Julian

I flushed mine with gasoline several times until it cleared up, then with the top off and the PTO cover off I sprayed the internals down with brake cleaner. With the clean interior I could see that the guts were in good shape, after it was back in the truck I filled it from the top and put the shift tower back on.

Buckshot, when I cleaned my engine, prior to paint, I was told to keep carb and brake cleaner away from the gaskets. Would carb or brake cleaner mess up bearings and all in the trans?

Gasoline and brake clean will do the same thing, gasoline will be cheaper. Fill it up run it a while with the drill or just slosh it around if out of the truck. Do this a couple of time and it will be clean with no harm done. Diesel and kerosine will also work, just not quite as aggressively. Once the gas drys out, fill with gear oil and slosh it around to coat the insides. My lawn mower has no drain plug, so I have to pull the engine off and turn up side down for draining, I then fill with gas to clean out the bottom. It hasn't hurt the gaskets yet! I work with a group of guys at work that love to use brake clean, I find its very hard on skin, and lungs, plus if the vapor get burned by a local furnace or fire, the results are very toxic. It does an excellent job of cleaning, just use it with caution.

Gas + agitation = fumes. Better be sure your drill motor brushes don't make a tiny spark while the drill is running. How's your fire and medical insurance coverage? Cast iron shrapnel from a transmission case probably makes a better bomb than a pressure cooker, too!
Jerry

GASOLINE???

I know it’s done all the time and I’ve done it myself many times in the past but Gasoline is just way too dangerous to use for cleaning. Why take a chance? Just takes one spark to really ruin a good day.⛽️❌