HST charge pumps

[TimJr]

I have a question about the HST in the 7100/90's Sovereigns and the Sunstar tractors.  I thought they used basically the same HST?  It's been a long time since I have been into a Sunstar.  

Why would the charge pumps have different part numbers between a 7100 and Sunstar HST?  Do the pumps rotate opposite directions?  

Or, is the Sunstar HST and charge pump larger?  They look similiar in structure, but might be different series/sizes.  Thanks, Tim

[Bill725]

The Sovereign uses a Sundstrand Series 15 u-type pump and I think the Sunstar uses an in-line like the Powermax.

[CarlH]

Sunstars use a u-type Sundstrand Series 15 also. All of the Sunstar hydro's appear to be the same spec (different from the Sov's) with a splined main shaft to drive the rear PTO's.  I found at least 7 different PN's used in Sovereigns.

[TimJr]

2 hours ago, CarlH said:

Sunstars use a u-type Sundstrand Series 15 also. All of the Sunstar hydro's appear to be the same spec (different from the Sov's) with a splined main shaft.  I found at least 7 different spec #'s used in Sovereigns.

Do you have a Sundstrand parts manual?  I see Simplicity has different part numbers for the charge pumps.  I wonder what is different about the charge pump.  Is it the housing or the inner gears?  Is it a larger ID for the different input shaft?  Maybe it is a higher capacity pump?

I know they are spec'ed for the same max charge pressure, but I don't have anything that shows me what the gpm of the Sunstar spec pump is to see if it is different than a 7100.

[CarlH]

55 minutes ago, TimJr said:

Do you have a Sundstrand parts manual? 

Nope.  Got my info from Simplicity doc's.

[CarlH]

PS:

Other brands (JD and Cub's) used the same U-type Series 15 Sundstrand.  I have asked myself all of Tim's questions and have no answers.  I suspect that the Sunstar hydro's have higher capabilities than the early 7000 Sovereigns.  I wonder if the green tractors with the H3 hydraulics are bigger also?   Info from Sunstrand might answer???  All I have is a service manual for the Series 15.

[ShaunE]

15 hours ago, CarlH said:

All I have is a service manual for the Series 15.

Exactly what I have.  The two from Simplicity & the one from Sundstrand.

[PhanDad]

1 hour ago, ShaunE said:

the one from Sundstrand.

Is it in the Downloads forum?  (Of course it might be paper)  

 

[Brettw]

Not sure, but I will say that the power steering in the Sunstars I have had always seemed to respond cleanly and quickly.  Not so much in the Sovereigns.  In fact, the Sovereigns were downright disappointing. And they both run off of a Sundstrand Series 15 and had the same steering sector (I believe). So they may have different outputs, volume and pressures?  Also, the input shaft is different as a Sunstar is shaft driven and the Sovereign belt driven.  As stated above, there is also a splined output shaft for a rear PTO on the Sunstar.  Sam case and basic pump, but there are differences.