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Hydrostatic Newbie-System Flush

F

Fritzhaus

New member
I just picked up a Lite-Foot (Pistenbully Scout) snowcat. It has the following components.

  • Sauer series 90 pump
  • Volvo F11 final drive
  • Auburn Gear hubs
The previous owner used it for cabin access and put a whopping 30 hours on it over 8-9 year. The fluid in it has 30 hours on it, but it's old. Current fluid is Chevron AW-32. Because it's so old, I'd like to flush and replace with ATF type F.

I'm not a mechanical retard (lots of experience rebuilding motos), but I've never worked on hydrostatic systems, so I'm looking for insight.

Here's what I think one would do to flush the system.

  1. Drain reservoir
  2. Drain pump
  3. Drain hoses at final drives
Refill process.

  1. Keep everything clean!
  2. Replace both filters
  3. Fill pump at upper access
  4. Fill reservoir
  5. Turn motor over with coil removed (30 sec)
  6. Repeat above step and check reservoir level
  7. Keep pressure gauge attached to M3 port, repeat above steps until spec'd pressure is obtained.
  8. Check reservoir level, fill as needed.
  9. Start engine, slowly cycle drives forward/backward for several minutes to remove air.
  10. Recheck reservoir level.
Thanks for any and all advice.
 
To me oil doesn't get old. It's already old. I would have a lab do a analysis of a sample before going to all the trouble. I realize what your thinking, as oil is cheap...I started a diesel engine with 14 year old fuel in it not so long ago and still haven't changed the more than 14 year old oil in the hydro stat for the ground drive. It was stored inside BTW...

If the fiters are doing the job, and there is no water in the system, I would be temped to let it go until the regular service interval. JMHO...

Regards, Kirk
 
Last edited:
300 H and H said:
To me oil doesn't get old. It's already old. I would have a lab do a analysis of a sample before going to all the trouble. I realize what your thinking, as oil is cheap...I started a diesel engine with 14 year old fuel in it not so long ago and still haven't changed the more than 14 year old oil in the hydro stat for the ground drive. It was stored inside BTW...

If the fiters are adiquite, and there is no water in the system, I would be temped to let it go until the regular service interval. JMHO...

Regards, Kirk
Click to expand...

Other stuff I've read says the same. Pay for the analysis first.

I'm neurotic when it comes to maintenance on my other vehicles, and if I screw this one up, it's pretty damn expensive.
 
Fritzhaus said:
Other stuff I've read says the same. Pay for the analysis first.

I'm neurotic when it comes to maintenance on my other vehicles, and if I screw this one up, it's pretty damn expensive.
Click to expand...

Yea especially toys that could not only leave you stranded but also embarrassed in a major way as well....:sad:

Run it a good bit to warm and stir the oil and take a sample of the tank and get it tested. Caterpillar dealers do this at about $25 per. My bet is that it's just fine.

Hope we all get some good snow,:clap:

Kirk
 
300 H and H said:
Yea especially toys that could not only leave you stranded but also embarrassed in a major way as well....:sad:

Run it a good bit to warm and stir the oil and take a sample of the tank and get it tested. Caterpillar dealers do this at about $25 per. My bet is that it's just fine.

Hope we all get some good snow,:clap:

Kirk
Click to expand...

Well, being stranded isn't a concern. I always have my backcountry skis with me, so no biggie. Plus, the cat is so damn big, it's like an small hut!

Anyway, thanks again, I'll do the test first.
 
if i were to change the oil it wouldn't be to atf i would use a synthetic oil like chevron clarity we run that in all of our equipment up here and it works good in the cold. as for the need to change i second kirks advice with juce drive tehre is a lot of oil it will be expensive and you would be well suited to have a sample anylized and change it when the lab tells you to.
 
Thanks for the replies.

Right now it has Chevron AW 32 in it.

I've called Pistenbully and Prinoth, and both have given me multiple different suggestions for fluids. Then on the other snowcat forum, a guy with 30 years experience highly suggests ATF-F.
 
the lubritcity of atf is lacking also if has a wet disc additive package atf belongs no place but in a transmission and not in engines or hydraulics you may also run into problems with seal compatibility with the detergents that are added
 
dds said:
if i were to change the oil it wouldn't be to atf i would use a synthetic oil like chevron clarity we run that in all of our equipment up here and it works good in the cold. as for the need to change i second kirks advice with juce drive tehre is a lot of oil it will be expensive and you would be well suited to have a sample anylized and change it when the lab tells you to.
Click to expand...

I checked the specs on the Chevron AW 32 and the Clarity. The pour point, viscosity, etc, are all very similar.
 
This is from Sauer-Danfoss.
Picture1-16.png
 
another synthetic fluid i have been using from another compaany i work for is amzoil both fluids have worked much better than conventional oils in extreem cold
 
I would be inclined to use ATF type A, since type F is tough to find in my area. Maybe you have a stockpile of type F, so use it. Looks like the oil spec sheet is acceptable to it so go ahead.
 
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