Little late on this thread... Sorry ... We had a 965C transmission fail at high speed as well. Upon disassembly we found much the same issues. One of the two planetary assemblies looked like it got hot and seized the planet gear. This shattered the gear and broke the main case. Most of the issues with these transmission was software or clutch pack related. We rebuilt lots of 865B and C series transmission and differential steering units.
In answer to your question I think high speed road travel is part of the issue but not the whole... Lube pressure in these transmission is low... Meaning RPM is key to correct lubrication of transmission...
The only other thing to watch out for is over filling the transmission. It will heat and cause internal damage...
Thanks 101, I really appreciate input from someone like yourself that knows these trannies from having been inside of many units over the years. The low oil pressure problem below 1800 rpm is
interesting, since that engine is designed to pull at least 300 rpm lower than that, and most guys think 1800 on the engine is max. So what, the transmission needs a larger flow pump?
A few clarifications on my transmission. It was a 2008 965B with 4400 hours. It had a major update done in the trans at about 1800 hrs. At 4000 hours when I bought it we pulled all the oils, filters, screens and opened up all the places where you can get access to look for cuttings or debris on the bottom of components. The hyd reservoir was really clean and there was a small amount of small pieces of clutch material in the bottom of the trans housing. The Agco tech working with me thought it was a normal amount and since no steel was present, we considered it a good sign. We have no knowledge of how long it ran on the present oil and filters either. We cut the filters and again found a small amount of similar material. He checked with Agco and they said it looked normal and everything should be good. We completed the oil change with all new filters and did a season of seeding putting on under 200 hours.
After this I again pulled the transmission filter and cut it open to inspect the filter paper. In a season of seeding there was absolutely nothing in the filter paper, telling me that there was nothing going on in the transmission at that time. I seeded one more crop after that and loved the tractor and how it pulled the drill at about 1650 rpm. I have one 1/4 that is quite hilly and shifted down one gear and increased the rpm to 1850. Impressive torque!
It was the following spring that the transmission problem happened at 20 mph on the road. At that speed the rpm must be up over 1800 so leaning back to the ground speed being the problem??? When the transmission was rebuilt last spring after failing, there was a bulletin calling for drilling out oil supply holes to a bigger size somewhere in the planetary area. So even after one level of updates to this trans, they are still admitting they do not have enough oil supply to the planets. At $50,000 a pop, they better get it right soon. This is beginning to sound like a class action may be needed. Especially since they accept no responsibility and will not admit that they have a problem at high speed. I have tried to suggest that they advise owners to impose a speed limit for the benefit of all, but they just will not talk to me now. I still say it is a great tractor, but nobody can afford problems like this. Thanks for all the input.