Sundstrand Series 15 on Gehl 2500 - Should I Pull Apart?

[Deke]

Hi Guys. Great website! I've already gotten some helpful info on here by looking over other posts... I have an old Gehl 2500 and left side drive motor stopped working. Hydraulic oil level was good... no leaks. I checked hydraulic pressure and charge pressure on left side pump/motor - both read 0. I finally pulled the hydrostatic unit and found that the pin that attaches the splined drive shaft to the pump input drive was broken... two pieces of it found, but I'm not sure where the rest went (maybe just ground up?). The input shaft seal appears to be okay... My question is, it was a pain to get the hydrostatic unit out of the skid steer... At this point, should I just buy a new drive pin and put it back together, or should I open up the pump/motor transmission unit to see what shape the internals are in? It's the U Type pump/motor combination unit... Not sure if I would need to get all new seals, etc if I pulled it apart. I don't mind doing some extra work now to save me from having to do it all again later, but I don't want to mess it up if it's not broken... Any thoughts or ideas? Thanks, Deke

 

[Deke]

Anybody care to give me their opinion? Ken, Tazza, OldMachinist? Sundstrand Series 15 pump/motor... Have it out of skidder now and found out why there was no pressure (sheared pin in input shaft splined drive)... Is it worth pulling it apart to look at rotating group and swashplates since it's out already, or are chances good that there's no internal damage? It was rolled around a bit loading it onto a trailer with a winch... and the check valve bypass clips were not installed, so I'm not sure if this would have caused any internal damage. Thanks again, Deke

 

[Tazza]

Anybody care to give me their opinion? Ken, Tazza, OldMachinist? Sundstrand Series 15 pump/motor... Have it out of skidder now and found out why there was no pressure (sheared pin in input shaft splined drive)... Is it worth pulling it apart to look at rotating group and swashplates since it's out already, or are chances good that there's no internal damage? It was rolled around a bit loading it onto a trailer with a winch... and the check valve bypass clips were not installed, so I'm not sure if this would have caused any internal damage. Thanks again, Deke

I don't know what pump that is, i have worked on a Sunstrand pump before, but it was from a Bobcat, not sure how close they are from model numbers. If the pump is out and the broken shaft section was enclosed in the pump, you will need to open it up. If it was all outside the pump there is no need to crack the pump open unless you had a drive issue before.
Did it drive ok? no loss of power? if it was good, i'd leave it alone and just replace the coupling. But i'd turn the shaft to make sure it hasn't locked up. The coupler had to let go fro a reason.

 

[Deke]

I don't know what pump that is, i have worked on a Sunstrand pump before, but it was from a Bobcat, not sure how close they are from model numbers. If the pump is out and the broken shaft section was enclosed in the pump, you will need to open it up. If it was all outside the pump there is no need to crack the pump open unless you had a drive issue before.
Did it drive ok? no loss of power? if it was good, i'd leave it alone and just replace the coupling. But i'd turn the shaft to make sure it hasn't locked up. The coupler had to let go fro a reason.

Hi Tazza, Thanks for your response... As far as I can tell, the pin sheared outside the pump input shaft seal and no damage was done by this - unless bits of metal were able to get inside the shaft seal and into the pump. The pump shaft turns easily, with no obvious hard spots or kinks. The thing I'm concerned about is that after left side stopped working, it was driven, shoved and towed (with a winch) up onto a trailer and then down again into my garage... I didn't know about the damage possible by not using the emergency check valve releases to let the motor and pump freewheel, so it was mostly forced to roll up and down the ramps - now I'm wondering if that may have caused any pump damage. (I read somewhere on this site about using special clips to release pressure when a unit had to be towed) In these Sundstrand Type U hydrostatic units, variable pump, motor and charge pump are all bundled together in one casing. I imagine if I did open it up, I would be looking for damage to the variable pump section, right? Aside from the time it would take (and the fact that I would need new seals), is there much danger in messing up the pump if nothing was wrong with it before? I'm not looking for more work - just would hate to get it all back together and change the fluid and filter, and then find out there's a problem in the pump unit... I can post a photo or diagram if that would help. Thanks, Deke

 

[Tazza]

Hi Tazza, Thanks for your response... As far as I can tell, the pin sheared outside the pump input shaft seal and no damage was done by this - unless bits of metal were able to get inside the shaft seal and into the pump. The pump shaft turns easily, with no obvious hard spots or kinks. The thing I'm concerned about is that after left side stopped working, it was driven, shoved and towed (with a winch) up onto a trailer and then down again into my garage... I didn't know about the damage possible by not using the emergency check valve releases to let the motor and pump freewheel, so it was mostly forced to roll up and down the ramps - now I'm wondering if that may have caused any pump damage. (I read somewhere on this site about using special clips to release pressure when a unit had to be towed) In these Sundstrand Type U hydrostatic units, variable pump, motor and charge pump are all bundled together in one casing. I imagine if I did open it up, I would be looking for damage to the variable pump section, right? Aside from the time it would take (and the fact that I would need new seals), is there much danger in messing up the pump if nothing was wrong with it before? I'm not looking for more work - just would hate to get it all back together and change the fluid and filter, and then find out there's a problem in the pump unit... I can post a photo or diagram if that would help. Thanks, Deke

I would doubt you'll have any damage from towing it. The motors are full of oil so moving the machine like this the motor will slowly turn, but its full of oil still so it won't be damaged.
As you mentioned the coupling was outside the pump, i'd just put a new one on and see how you go. I can't see anything that you have described damaging any part of they drive system. Rolling the machine will move oil, if the pressure gets too high the relief in the pump would open.
If the pump was good before, i wouldn't open it up.

 

[Deke]

I would doubt you'll have any damage from towing it. The motors are full of oil so moving the machine like this the motor will slowly turn, but its full of oil still so it won't be damaged.
As you mentioned the coupling was outside the pump, i'd just put a new one on and see how you go. I can't see anything that you have described damaging any part of they drive system. Rolling the machine will move oil, if the pressure gets too high the relief in the pump would open.
If the pump was good before, i wouldn't open it up.

Okay, Thanks Tazza. I'll give it a try. Best, Deke