450C Loses drive power when hot

[NIKinNZ]

OK, having stumbled through a few issues with my 1976 450C and receiving a lot of help on this forum i would like any suggestions as to what may be causing this issue:-

Once the machine is hot (been operating for 20-30 mins) it loses pushing power i.e if pushing dirt it just wont push, the engine is still running as it should but just no pushing power, if i then put the machine in to reverse, it will reverse OK on the flat but if i start to reverse it up a hill it will start to climb then lose driving power (wont continue reverse climbing) and just stay in one spot. But here is where it gets weird, if i am 1/2 way up a hill (in reverse) and it does this, and i put the front blade down (to keep me there) then switch the machine off and wait 2-3 mins, then start it again and put it into reverse, it will allow me to reverse for another 10-20 feet then do the same. If i leave it there and let is cool for 1-2 hours, i can start it and operate it for 10-15 mins with no issues.

I have plenty of transmission fluid.

Any suggestions would be appreciated. I did have a prior oil leak (which seems to have stopped) and i think it may have been due to previous overfilling. Someone suggested it is a transmission pressure issue? any fix solutions?

Thanks in advance.

[Jim B]

You need to get your technical manual out and do the checks and diagnostics to try and narrow the cause down. Sounds like a pressure issue. Could be pump, valve, or seal related. Could be the engine clutch slipping when hot. You need to do the diagnostic work.

[NIKinNZ]

Thanks Jim,

Yes i have been going through it, it points to so many potential issues that i was hoping someone may have had the same issue and could point me down an avenue to avoid me wasting more time. Thanks again, Nik.

[Jim B]

At this point someone might throw a suggestion out that hits the cause and fixes it for you. To me that is just luck and more time can be spent chasing "maybes", than biting the bullet and methodically doing the checks.

Since it loses power in both forward and reverse, the cause would seem to be common both the forward and reverse clutches. To me that makes pressures the most likely cause. Whether it is a pump or valve issue takes the testing. The engine clutch is another thing common to both forward and reverse. How is your clutch pedal free play?

[Lavoy]

The longer you run it, the more chance you are burning the clutches. I would find the problem immediately and fix it, or you are adding a trans tear down to the list.
Lavoy