Cat 525 grapple skidder transmission issue when hooked to large pull? Fluid type?

[lectrocrew]

This transmission is the original with >15,000 hours. It pulls good with medium loads but when hooked to a large load the trans will start to pull/no-pull/pull ect. with about 5 seconds between. This is regardless off whether in 1st or 2nd gear (or 3 or 4, but I rarely pull in 3 and never in 4). It also will stick in reverse gear whether forward is selected or reverse and vise-versa. It will always shift to neutral correctly when selected. Once this issue starts there seems to be nothing to correct it, including complete cool down of the machine. It will return to normal operation at some time (not sure yet what criteria is involved with this return to normal?)
We have replace the $198 transmission direction control switch on the steering wheel but it had no effect on this problem).
My boss is a struggling logger and can't afford the cost of Caterpillar to send a mechanic, but...
One issue that concerns me is that he has been using Shell Rotella/Chevron Delo 400 'motor oil' in this transmission, which leaks ~ a gallon per 40 hours of operation because he says it's cheaper? I don't agree with this but it's his machine and he is hard headed/un-educated on API oil standards...
My main question is if using the improper oil can result in this type of symptom since I disagree with his use of motor oil in the transmission, but any other information is appreciated since I need this machine running so I can have a paycheck.
Thanks a ton for any help!!!
Mike

 

[treeclimber101]

This transmission is the original with >15,000 hours. It pulls good with medium loads but when hooked to a large load the trans will start to pull/no-pull/pull ect. with about 5 seconds between. This is regardless off whether in 1st or 2nd gear (or 3 or 4, but I rarely pull in 3 and never in 4). It also will stick in reverse gear whether forward is selected or reverse and vise-versa. It will always shift to neutral correctly when selected. Once this issue starts there seems to be nothing to correct it, including complete cool down of the machine. It will return to normal operation at some time (not sure yet what criteria is involved with this return to normal?)
We have replace the $198 transmission direction control switch on the steering wheel but it had no effect on this problem).
My boss is a struggling logger and can't afford the cost of Caterpillar to send a mechanic, but...
One issue that concerns me is that he has been using Shell Rotella/Chevron Delo 400 'motor oil' in this transmission, which leaks ~ a gallon per 40 hours of operation because he says it's cheaper? I don't agree with this but it's his machine and he is hard headed/un-educated on API oil standards...
My main question is if using the improper oil can result in this type of symptom since I disagree with his use of motor oil in the transmission, but any other information is appreciated since I need this machine running so I can have a paycheck.
Thanks a ton for any help!!!
Mike

I am no mechanic but is it supposed to run on trans fluid or heavy weight gear oil like 80w , that can destroy the transmission. With the quickness , it gets real hot in the there and water doesn't coat parts very well . That's why they recommend a heavy gear oil or a trans fluid with high zinc