I'm working on a cat 963, I have rebuilt the hydrastat, took the valve body apart checked all the orfaces, checked for debre in pressure valves, After all that took the machine outside to try it out and at full rpm it creeps along and as the throttle is moved forward it speeds up. I have seven pressure gauges on this machine and everything seems to be OK and in spec. The only thing i noticed is there is an X at the end of each casting number. So this transmission did not come in this machine. Customer bought it at an auction and thought a drive motor was out, nope rotating pump barrel on the right side. This isn't my first cake walk on cat hydrastat trans. never had this kind of trouble before so can someone tell me what I'm missing. Any suggestions are appreciated. :Banghead
I suspect this is an old HPCU machine if you throttle down the underspeed override control will cause this. Change the filter and cut it open to find debris. What oil are you using ? Need 10W. Come on back with what you find. Later Bob
Bob, Have been under the weather last 5 days, but the filter has been changes three times, never found any debris we even used a magnafying glass, once we tried it without a filter, didn't help. Now I wonder maybe since this HPCU was made in Japan all the seals that we put in using the machine serial number are maybe wrong on the actual sizes mm/inches?
Doesn't matter where the HPCU was made (so long as it's a genuine Cat one) - using the seal Part Numbers that are shown in the Parts Book for the Serial Number of machine will get you the correct parts. Everything appears to be inch sizes, the O-Rings certainly are anyway.
They are very similar. Your problem is lack of flow through the venturi. If you are getting full RPM, the filter is clean and you are using the correct filter and 10 W oil I suspect the filter bypass valve is stuck open. Low flow simulates low engine RPM and prevents the Underspeed valve from coming up fully. When you throttle down the override valve allows it to come up. Later Bob
Bob, Thank you for the explanation of what is happening, some of old foggies if 62 is old don't quite cautch on as fast as we use too. Also it did have the WRONG FILTER, according to the parts book. When i gave Cat the number in our book the number changed 3 times. The oil that is in the machine has a lower pour point than 10W engine oil, so I think I'll keep it the same, and see what happens. Thanks so much for the use of your knowlage! Maurice
I'm a bit older than that Maurice and still learning. Something just occurred to me, work has been done so there might be R&I problems. Better go over all linkages. Start with throttle, pull right back and look for 5/8" stretch of the spring link. Then look at the speed/brake linkage. With center pedal up you should get a 5/16" bolt to go through the lever and thread into the valve. Make sure both steer pedals are free and not sticking. Later Bob
Maurice, that's the problem with paper Parts Books, especially for a machine that's a few years old. However if you give the number from the book then no matter how many times that number has changed since you should get the latest & greatest replacement. One word of caution/advice though, if the dealer tells you that a Part Number has changed (whether once or more) from the number in your book, ask them to double check if any additional parts might be required to install the replacement part they are selling to you. There are times when something changes and in order to install the replacement Part Number you have to have other parts as well or it won't fit. The dealer Parts people should tell you if this is the case, but if they don't then be sure to ask them.