I haven't smell anything, but the fluid was Black & Gritty. I really don't know if the owner of the forklift put in the wrong trans fluid.

After flushing the system out 4-time. I replaced the fluid with Amsoil and add trans fluid conditioner. Hope that would stop the deterioration of the plates and improve the rubber seals in the trans. If trouble starts again, guess got to rebuild the trans.

The only time I've seen grit/chunks of disc friction material is when a wrong type of trans fluid is used. Usually a trans which has pressure issues which cause the friction plates to wear- the material coming off the plates is extremely small, not gritty & the trans fluid smells burnt- it really stinks. Did yours have a strong odor of burnt fluid?- I suspect not.

I have run & driven the forklift between changes, so the torque convert should be flush as well.

This Screen Filter between the Control Valve (Forward/Rev Solenoid) and Valve Body. I don't see it. I have washed and blew out the Solenoid many time. I don't see any mini screen any where. How can a 3,000-hours trans burn up so quickly and deteriorate?? Very hard to believe??

Does any body know how much a Reman-Transmisssion cost about?

Sounds like a trans flush is in order at a minimum ( the kind in the automotive world- where the engine is running & the trans cooling lines are connected to a fluid flushing machine).

I must admit that the debris in the oil is a very bad sign- I'd prepare the customer for a trans replacement/rebuild.

Keep in mind that torque converter is full of that dirty oil, that doesn't come out, when you pull the drain plug.

edward is correct, you cannot go by 'feel' , you have to use pressure tests to know what is going on inside these transmissions.
flushing the transmission case with diesel fuel is not going to get you a good cleaning so you will have debris floating around. It would take several fluid and filter changes after running the lift to get the fluid clean OR pulling the transmission and disassembling it and cleaning it which would be during a rebuild generally.

also there is a screen nobody thinks about that is in the control valve area which is what in training we were instructed to call the 'last chance filter'. It is a small screen in the ports between the control valve and the transmission body, it is not shown in the manual either, it is part of the assembly and if it gets clogged that will throw pressures off and could keep the truck from pulling. Also check the strainer located in a plug under the solenoid valve chamber.

If you want to see the condition of the plates you can pull the control valve and take a physical look at the plates if you like, you can usually get an idea of what condition they are in that way.

I think you'll find if you have that much debris floating around inside the unit these plates will be worn out.

I suggestion would to be start looking for a reman transmission unless your in the mood to rebuild one.

you say "trans does not slip", ?is that from feel, or from taking pressure tests?
These trans don't really -feel- like they slip until the pressure is lower than about 75 PSI, but it -should- be around 150 to 175 PSI, (someone else can look up the exact numbers for us) and IS slipping the clutches at lower pressures (like riding with the operators foot resting on the inch pedal).
Disassemble the inching linkage bell-crank, and lube the shaft, so that it moves freely.