Transmission pinion will force the bevel gear/crown wheel (the tractor is fitted with a crown wheel and pinion the same as in a car diff) to one side the other side is loose and flogs around, the steering clutch hydraulic seals would take a flogging and not seal properly, hence not enough oil pressure to force piston to release steering clutch.

Gotcha! yes sir, we are on the same page with this, and I did run into a drawing that shows the piston you speak of. Seems to work inside the "hub"? But they showed a hydraulic puller to get the hub off. Does not look too fun. More worried about dropping something...lol I think there is just enough pointing towards those bearings they replaced being FUBAR or not tight. But why they were hammered in the first place is what I really want to figure out.

contractormag.co.nz/classic-machines/caterpillar/d7/

Oh, here is a pic of my exact machine. She is famous! They grabbed a pic from a previous sale of it. I was shocked to see my bird! I sure hope I can get her back.

Now I see a photo of your tractor, it appears to be bare backed, so should make a test easy. You can remove the round cover on the rear, will give you access to the bevel gear. You then could use a pry bar to see if there is any movement.

Wombat

So.....I found a sort of hydro schematic. It does appear the second screen filter near the waterpump is a second chance filter for the TC so I will just have to hope and pray.

On the schematic, the TC charge pump and filter are not even on it so obviously not a very "complete" schematic. The only way I am getting to that filter is through an access plate on the belly pan.

Question for anyone that might have turned wrenches on these, is there any chance at all I can get the cooler out without dropping the belly pan? I am really trying to avoid extra labor until I know we have something and that task is both a serious pain, and dangerous. If it has to come off, advice on removal would be awesome. Appears the pans have had some abuse so install will really suck so avoiding that would be great.

Yes the crankcase guard has to be removed. Transmission jack or come-a-longs to lower/raise guard.

The guards are not that bad. I have been in on bigger than a D7 out in the soft dirt no jack needed.
Two cable come alongs and chains from top of one track to the other. Good come alongs that have not been abused helps with the letting it down one notch at a time.

Thanks. this gave me an idea to use two long straps as cradles for the pan and connect them to the exavator bucket above so I can easily lower them. I will need to run some numbers to determine pan weight, but thinking around 1000#. I do that math daily but didn't even look yet.

I think the cradle idea will give me some comfort as I can run the straps and get serious lift force on them before attempting to break some bolts free. If the cradle works, I can just lower it to the ground, but will have to think about getting it pulled out of the way. I know I will need to drag machine around a bit just to rotate clutches for removal, but still not sure what will be needed there.

Something I was pondering is if engine oil has an opportunity to communicate to the trans oil? The trans oil is way darker than I have ever seen. Enough to make my mechanic brain think hard about that. All this oil was replaced only 60 days prior. It is possible the trans oil was NEVER changed, thus the reason for the color as one oil change would not do a good rinse, but......that is a stretch. Also considering the interaction of coolant with very hot oil. Usually you get a milkshake.

Engine oil can enter via the rear crank seal and the transmission steering clutch pump seal. The front crankcase guard weighs 375 lbs without dirt, the rear guard weighs 350 lbs.

Are there any tests to determine cross talk between engine and trans oils at the rear main? It would seem there is likely a shaft seal on the TC where crank power is delivered? I can nearly guarantee that was replaced when the TC was rebuilt, but not really a guarantee it isn't leaking.

And regarding the steering pump, I am confused as I understand the main "trans pump" to deliver oil to the clutches? The one sitting just right of the TC that you can kick with your foot from the operator station? I figured that one had TC trans oil on the drive side? Or another pump yet?

I guess it is possible things were contaminated from the previous TC failure in which maybe engine oil got in, but I would think the dealer would have dealt with it. Just trying to cross more T's before diving in.

It's the pump just ahead of the engine accessory drive housing on the right above the magnetic strainer. Most likely the seal is bad on the pump and drawing engine oil in.