Gear pump on Sundstrand U15

Jim1934 · #1 09-19-2021, 11:32 AM

New here. I have removed the tranny and Sundstrand U15 hydro from a 1650 cub cadet.
Cannot get output of hydro motor to turn when powering input ccw.
Question involves correct mounting of the gear charge pump.
On one end of its casting is a flat spot. Does that flat point to swash pump actuator(speed control) or the other side.
Have tried all combinations and non work so I want to be sure I have it correct
so I can go on trouble shooting.
Thanks, Jim in mich.

ironman · #2 09-19-2021, 12:48 PM

I am not experienced enough in these units to answer your question. However, others here are, and should soon be along to help you.
In the meantime, here is a link to a service manual that may help you....

https://assets.danfoss.com/documents...7en-000101.pdf

SLS327 · #3 09-19-2021, 09:09 PM

Service manual for 1650 page 2-44, flat side goes to right side of machine. This would be opposite swash control lever.

Cubcadet_107 · #4 09-20-2021, 09:13 AM

Have you looked into the relief valves on top of the pump? If they aren't functional then the system won't build any pressure and the tractor won't move.

Also, its kinda a rare occurrence but, can you spin the output shaft on the pump? Or is it locked up?

Jim1934 · #5 09-20-2021, 10:16 AM

Thanks for the replies.
I read the service manuals "right side" but that leaves the question of
which is right side. Also confusing me is that detailed drawing of the unit clearly shows
flat side on same side as swash actuator.

Yes, I had both check valves repaired. Am interested in the bound-up question.
Certainly not mechanically as I have inspected guts and all looks new. Cannot turn motor output by hand, but assumed that is because of spring pressure in piston assembly.

I have been driving pump at 1000 rpm; today I plan to try 2000.
Jim

Cubcadet_107 · #6 09-20-2021, 10:41 AM

Quote:

Originally Posted by Jim1934

Cannot turn motor output by hand, but assumed that is because of spring pressure in piston assembly.
Jim

As long as there is no pressure in the system, you should be able to spin the output by hand. It probably won't spin easily, but it should spin.

The right side of the unit is on the side opposite of the trunnion and hydro linkage. When you look at the pump from the front it'll be the left side.

Another possibility I have just thought of is, maybe the charge pump has failed and just isn't functioning at all anymore. I do believe members here have had that issue in the past.

ironman · #7 09-20-2021, 10:57 AM

You may want to read this thread (to the end)....
https://www.onlycubcadets.net/forum/...ad.php?t=30840

ol'George · #8 09-20-2021, 05:20 PM

FWIW:
When sitting in the operator seat, left and right is most generally determined by that of the operator, not by a bystander.
That said, there are a few exceptions like a tractor that had been modified to be used as say a hilo.
Or using a TLB (tractor loader backhoe)
Turning the seat around to operate the ho' does not change left or right.
Did I need to mention that?

Jim1934 · #9 09-20-2021, 08:09 PM

I have read all the posts and on line manuals and charge pump has flat
on right side. Have driven it both cw and ccw but convinced ccw correct.

Output shaft is tight. This version has a tapered roller bearing. Normally
manuals specify a preload. I see no provision for or info on same.

I am giving up ( aah) after four disassemblies, replacing oil seals, and check valves.
Perhaps I have some parts in upside down, or output shaft is too tight.

Thanks to all for responding. If I find solution will report.

Jim

Jim1934 · #10 10-02-2021, 11:57 AM

Pressure at Gear Pump test port is 50 psig when driving pump at at about 1000 rpm and
auxilary( lift ) ports connected together with a hose.
Hyd. motor does not rotate. That is the problem.
I have no provision at test set up to drive it any faster.
Service manual doesn't show any other test ports. Appreciate comments.
Thanks!