I went through the 518 in my 92 D250 less than 8,000 miles ago. The non-lockup converter was tightened up too. It got all new friction materials and seals.
The truck doesn't get driven much. Most of it's time is spent sitting in the drive.
Over the last few months it developed a habit of being a bit weak until the fluid was warm. It was slipping a little when I accelerated with any enthusiasm. Once there was a little heat in it things were fine. It worked great. I noticed it more in reverse and first gears.

Today I went to move the truck and it would barely go. There's a small bump in my driveway where the pavement is broken. The truck could not pull itself over that bump. I opened the door and pushed on the ground with my foot and the truck went over it.

The fluid is still more pink than red, there is no debris, and there is the slightest hint of a burned smell. The smell is nowhere near as bad as when I fried 727 transmissions in the past.

I'll try checking the band adjustments but I have the feeling it needs to come out.

Any other suggestions?

The pink is because the fluid is aerated, probably pinched a seal on the rear clutch piston... Hows reverse? Only gear that doesn't use that clutch pack...

Might help

Thanks. I was using my FSM and looking at the same info. There is nothing that applies only in reverse.

True but there is the low/reverse band which if it doesn't apply in low gear the truck will still accelrate normally due to the sprag/over running clutch... It just won't have engine braking...

Gotcha.
I just did a quick lap around the block before seeing your post.
It works fine (didn't check engine braking) in everything except reverse. It will back up but will shudder a little and slip if throttle is applied.

Rear band or front clutch?

Manual low works fine.

Just ran it again. Manual low works but no engine braking. Reverse slips.

Rear band?

Possible rear band but probably the apply piston.... Pull the pan, good chance it can be fixed in the truck...

Thanks.

Looks like I have one more project for next weekend.

It does feel like it's snapping into gear but the gear won't hold any torque above idle. I assume the piston is applying properly but the band needs tweaking.
I'll have to shoot a little air in the apply hole and see if the piston is sluggish or not reaching full travel. The pan will have to come off anyway.