seems like you might be low on oil in the transmission..when my 977K did this it ran fine and shifted fine,then gradually the trans slipped and then the loader stopped moving all together,in any gear,forward or reverse.Turns out I blew a o-ring in the torque converter oil cooler feed line and gradually dumped ALL the trans oil onto the ground(via the bellypans) Refilled the trans and it started moving again,no problem and shifted fine.Got it back to the shop and replaced the o-rings in the cooler hardline right at the oil cooler and all is well now.Pull your L side engine cover and look down at the cooler feed and return lines,chances are you might be dumping your trans oil into the chassis causing the trans slipping due to low oil.just my 2cents

You can block the tracks up and drop trans out the bottom. The 13X modular platform is more work to get off than 85J floorplates.
The external leak is the first to check and correct, it will let pump take in air and sound like it's pumping a bunch of marbles.
Then get a hose and 600 psi gauge into filter top to check pump pressure at high and low throttle in all gears to check for internal leaks and pressure control valve function. There is much work before deciding trans has to come out.
Later Bob

"bob" wrote:

You can block the tracks up and drop trans out the bottom. The 13X modular platform is more work to get off than 85J floorplates.
The external leak is the first to check and correct, it will let pump take in air and sound like it's pumping a bunch of marbles.
Then get a hose and 600 psi gauge into filter top to check pump pressure at high and low throttle in all gears to check for internal leaks and pressure control valve function. There is much work before deciding trans has to come out.
Later Bob

I'm sorry but I need a basic lesson in power transmission 101. It appears that the engine drives the torque converter via the input shaft, and then the torque converter does its thing and transmits the power to the tranny via the clutch packs ect. Where does the pump that your refferring to come into the picture? Do the clutck packs lock up via the pressure. And if that is the case, then all the cluch packs are slipping?Sorry for such a stupid question. LOL

Put guage on filter lid 300 cold wide open ,200 low idle. After machine warmed up (aprox 15 min running around and pushing a little) pressure was 200 wide open, 100 low idle, machine was stalling tracks easily almost wouldn't pull itself back to shop.When machine was cold and pulling good, pressure in all 3 forward/reverse speeds were 300,when I shifted it would drop down temporarily then go to 300

I think you may have graduated PS Trans 101.
Under the floor plates down on the Front LH side of the trans are two pumps mounted back to back on the opposite side of the trans/ torque housing from the Hyd pump. The front one is the trans pump and the rear one on the back of it is the steering pump.
Take them both off and take the trans pump apart and come on back with what it looks like inside.
Later Bob

Hey Bob I really appreciate your replies! I just went out and looked at the pump you were talking about. I hadn't seen that one, only the main hydraulic pump, and I couldn't figure it out. It's all starting to come together. I'll try and get it out tomorrow or Thursday and get back to you. Thanks!

I suspect the trans pump is worn out. If it is don't just put a new one on. There is a bit more work to do yet. Get back here before buying parts.
Later Bob

Took pump apart and there was some light grooving on both sides of housing of the gear that runs the other pump. Gears themselves looked good. Pump appeared to have been replaced because of no paint/rust and actually some bare looking steel.Can those be serviced at all, or just go with new? Or could it be something else?

Can you take a pic of the side plates and send to me by email?
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There used to be lots of parts but now they sell "Classic Parts" aftermarket I wouldn't want to mix cat parts with aftermarket pump if you could still get them. Might not be an exct fit. The wear was what I expected you would find. Take a jacknife and feel into the drive splines and look for a worn step at the spot the trans pump shaft ended. That wear will ruin a new pump fast, it forces the drive gear back into the rear end plate, can cut in 1/8" some times. The wear on the front housing is from worn drive tang on the steering pump, it will force the gear forward when the steering is under load. Fortunatly the drive gear is symetrical and you can take it out and turn it over and use the unworn side of the splines. You just need to take the hyd pump off to do it. That is why I said not to buy parts yet. How where the mounting seals? The pump picks up oil and pumps it out through the case I think. Where all the seals in place and still good?
Later Bob

Unfortunately, I'm pretty illiterate when it comes to electronics. I've got a new digital camera, and 6 computers, but don't really know how to use any of them. I might be able to find someone to do it for me however.All of the mounting seals looked very good. As far as the worn drive tang goes, is there any easy/quick/ cheap fix for that? Also can a shop resurface the housings and if so ,how is the O-ring groove affected.Once again, I really appreciate you help. I would have never known about the worn drive splines, ect. Apparently the last guy didn't either.