751c drive issue

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chaz071

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Oct 13, 2008
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Hi there guys, new to this forum hoping somebody can help. My 751c has nearly lost all drive to the right hydrostatic when reverse direction is selected. The pump loads up normally but the machine turns real slowly. Not sure yet if it changes when cool. Not a drive chain issue, reluctant to swap motors as I am pretty sure it's a big job. Oil is maybe 10 hours old as are hyd filter and bronze screens. All help much appreciated.....
 

Tazza

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Dec 7, 2004
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Swapping motors is quite simple actually, 4 bolts 3 hoses.
I would suspect bad motor seals on that side or a problem with your relief valve in the pump. Each hydrostatic section has a relief for both forward and reverse. As you only have a problem in reverse i would suspect a relief. The bad part is the motor and pump needs to come out to gain access to two of the reliefs. I am not sure if the ones on the top are for forward or reverse. As Murphy's law dictates, it will no doubt be the ones on the under side...
I have a 751c that I'm working on, motor removal isn't THAT hard and changing motor seals is easy too. You are looking at about 80 USD for a seal kit if you kit the motors out.
 
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chaz071

Member
Joined
Oct 13, 2008
Messages
10
Swapping motors is quite simple actually, 4 bolts 3 hoses.
I would suspect bad motor seals on that side or a problem with your relief valve in the pump. Each hydrostatic section has a relief for both forward and reverse. As you only have a problem in reverse i would suspect a relief. The bad part is the motor and pump needs to come out to gain access to two of the reliefs. I am not sure if the ones on the top are for forward or reverse. As Murphy's law dictates, it will no doubt be the ones on the under side...
I have a 751c that I'm working on, motor removal isn't THAT hard and changing motor seals is easy too. You are looking at about 80 USD for a seal kit if you kit the motors out.
Cheers tazza, i was reading your post about the burnt out one. I expect you're right. The motors both power forward eliminating the pump in my head. So does the right reverse hydrostatic circuit have 2 relief valves? Meaning the machines hydro drive sys has 8 in total?? Rob
 

Tazza

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Staff member
Joined
Dec 7, 2004
Messages
16,829
Cheers tazza, i was reading your post about the burnt out one. I expect you're right. The motors both power forward eliminating the pump in my head. So does the right reverse hydrostatic circuit have 2 relief valves? Meaning the machines hydro drive sys has 8 in total?? Rob
The hydrostatic circuit actually has 4. one for left forward, one for left reverse. One for right forward, one for right reverse. They are set to about 5,000 PSI from memory. If you remove the plate on the top of the pump that centres the steering you will see 2 plugs with an allen head hole in them, these are your relief valves. There will be 2 on the top 2 on the bottom.
You then have your main hydraulic relief but thats not an issue.
 
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