873 Gear Pump

[zteba]

Hey all, New guy to the forum here. Im replacing the gear pump on my 873 and wanted to know if anyone knows the torque specs for the two mounting bolts. Also if there is anything else i should be aware of while replacing the pump? This will be the second time now because the casting on the first pump cracked after only one hour of run time. The manufacturer said this was due to uneven torque on the mounting bolts, which im having a hard time beleving. Any help would be great! Thanks, Alex

 

[Tazza]

I highly doubt that was the reason...... They should have a little play to take up any un-even pressure on them. If anything was going to fail from un-even torque it would be the shaft, not the housing.
Sorry, i have no torque specs...

 

[OldMachinist]

I highly doubt that was the reason...... They should have a little play to take up any un-even pressure on them. If anything was going to fail from un-even torque it would be the shaft, not the housing.
Sorry, i have no torque specs...

I don't have a manual for a 873 but I looked at the 843, 863, 763 and the 773 manuals and they all say 25 ft lbs for the flange bolts.

 

[Fishfiles]

I don't have a manual for a 873 but I looked at the 843, 863, 763 and the 773 manuals and they all say 25 ft lbs for the flange bolts.

Where did it crack at , I see alot of Bobcat gear pumps crack , every time it is right thru the threads of the pressure port , there are two different fittings they used over the years in that port , one problem that is common is blowing the oring on the pressure fitting , and it really doesn't seem to me a different on helping stop the cracking -----------maybe you should check your pressure setting as it may be too high ---------

 

[cnord]

I have seen on the aluminum pumps where someone has started both bolts, but then tightened the one all the way in, and the other bolt puts too much pressure on the housing of the gear pump. and that pressure will break the casting part where the bolts go through. To fix that solution, you have to evenly tighten them both in. Two or three turns on each side till there both in enough not to put any pressure on the housing. I have a picture of this but I don't know how to post pictures on here yet.

 

[Rich M-37]

I have seen on the aluminum pumps where someone has started both bolts, but then tightened the one all the way in, and the other bolt puts too much pressure on the housing of the gear pump. and that pressure will break the casting part where the bolts go through. To fix that solution, you have to evenly tighten them both in. Two or three turns on each side till there both in enough not to put any pressure on the housing. I have a picture of this but I don't know how to post pictures on here yet.

zteba, In my service manual revised Jan 1999 It lists both the single and double gear pump use 25-27 foot lbs, as the torque spec. Rich m-37