I dug into a friend's 46rh today. The 165,000 mile truck is a recent low-buck purchase that would not move in any gear. No unusual sounds. He pulled the transmission, drained it, and did a thorough cleaning before bringing it over. He said the pan was full of thick nasty stuff.

The first thing I noticed is that there is a heavy varnish on everything. The second thing was that the fluid was not red. In fact, it looked about like relatively clean engine oil. The fluid in the servos was slightly pinker than the rest. The fluid does not smell burned.

After tearing it down, I found no broken parts. Nothing was burned. A few of the bearings are worn as was the thrust bearing for the rear planetary. All the friction surfaces look serviceable. The filter, however, was absolutely disgusting.
The bottom of the drums were caked with garbage. In fact, most things are caked with the stuff. There are signs of rust on many of the parts. The ends of the pinions for the planetary gears are especially nasty.

I did notice slight pitting on the gear and rotor for the pump. Those parts will be replaced.

He has had the converter rebuilt with an upgraded clutch and tighter pitch to better suit the stock Cummins.

Any idea what the culprit might have been? All I can think of is improper lube and a horribly clogged filter.

The fluid and varnish can be seen in this pic:

Those run the ATF-4, right?
A mechanic pal told me that there was a little known issue of water contamination in thr trucks. The A/C drain is just above the trans dipstick and if the dipstick seal is compromised, the A/C condensation migrates into the trans. That could be the cause of the rusty areas inside. I'm sure that water mixed with ATF would result in a sludge of some sort.

Check the trans cooler for blockage,if unsure just bypass and install a good cooler. Hard to say from here but converter clutch failure is a problem that often kills a fresh rebuild.

All the cooler lines are getting a good flush after seeing the guts of this thing.

I suspected converter clutch failure due to the amount of gunk despite having good friction materials. However, I wasn't there when the rebuilder cut the converter open.

Sounds like you were not there when the pan was cleaned either? Build it and see that the converter is right along with the lines and Cooler and you'll be ok.

To me it looks like it just got hot from sitting and idling, Remember it doesn't pump in park and seeing it's a diesel it probably did that a lot. I would install a manual valve that make's pump in park, Many trans suppliers sell them.

Rust inside of trans? Flood car?

I have seen fluid like that before, burned up TCC if I recall correct. The rust on parts doesn't sound good, thats really odd.

HOw long had it been sitting without being moved?

Sounds like that's where the rust came from to me.

I think it sat for a while after the transmission quit. The front drum has minor surface rust on the band contact surface. You can see it in the attached pic.

All I did was tear the transmission down. I was not around when he dropped the pan and cleaned the outside of the transmission.

Could have had engine oil in it but it definitely looks like it got some water in there .

Either way, it's not pretty. Unless it's fluid related I don't see any reason for the failure.

VARNISH!
This simple word is on every lubrication engineer's mind these days. It plugs up passages, gums up sliding parts, and generally makes a mess.
Varnish is actually very tiny soft particulate that is caused by breakdown of the oil. Water seems to be one of the culprits in forming varnish.
Varnish can actually be filtered out of a lubricant by use of special filters that have a special molecular attraction for the varnish. Electrostatic precipitators are also being used.

Varnish is deposited at lower temperatures. Higher temperatures keep the varnish moving with the oil.

At my work we are having problems with varnish causing hydraulic valves to stick. When the spring is supposed to push the shuttle in one direction the shuttle doesn't move and the hydraulic system doesn't work. If clearances are small, it doesn't take a very thick film to stop the valve.

R.

Getting that varnish out of there is going to be quite a chore.
It's so thick that I had to fight the servos to get them apart after the snap rings were removed.

Mineral spirits works ok for removing it. The hot tank at work doesn't take it off but it will soften it up. Sometimes we use a combo of the hot tank to make it soft and then brush it with the mineral spirits to get it off.