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Discussion Starter #1
We have a cat 65C with just over 4000hrs. Have discovered the transmission is overfull of oil and hydraulic tank is low. I believe it can only be one of the pumps driven of the gearbox that is the problem.Main pump on the front and two smaller ones on the back. One of the back ones is piggy backed, how to work out which one is my problem. Any experience out there thanks for looking cheers WF
 

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Don't over think and reseal all the pumps that use hyd oil driven off the transmission. That is how I would do it. May want to take the whole pump to a hyd shop and have them reseal them. They may be able to tell you if the whole pump needs rebuild and that is why the seal is leaking in the first place.
 

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We have a cat 65C with just over 4000hrs. Have discovered the transmission is overfull of oil and hydraulic tank is low. I believe it can only be one of the pumps driven of the gearbox that is the problem.Main pump on the front and two smaller ones on the back. One of the back ones is piggy backed, how to work out which one is my problem. Any experience out there thanks for looking cheers WF
Did you drain out the excess to see how much leaked in. I think there is steering direction valve that can leak oil in tranny
 

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Discussion Starter #4
I haven't drained any out yet but probably 20 litres overfull. I suspect a lot of it has leaked in while it was parked it has had very little use since last cropping 10 months ago.
Gearbox is a seperate unit with its own oil supply. Only way for hydraulic oil to get in is via hyd pump driveshafts.Thanks for looking all suggestions welcome.
cheers WF
 

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It’s pretty common on some of the forestry machines that I work on for pump shaft seals to leak after awhile. If you can get a make and model number off the pump a good hydraulic shop should be able get you a seal kit for the pumps. Some pumps have a seal carrier held in by an o ring and circlip and after awhile the o ring loses tension and the seal carrier starts to spin. It’s a relatively straightforward job once the pumps are out.
 

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Discussion Starter #6
Shimffy is likely on the right track. There is a small bleed off line from the steering direction valve. Caught up with a cat mechanic who has been around long enough to know where to look for factory information bulletins that detail testing procedure so we will start there.
thanks WF
 
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