Sunstrand Hydro - Squeals like a pig - SUDT - Or?

[Carl_NH]

Cub 1811 650 hrs - owned since new - always have had Hydro whine and some squeal but did a Cub Hydro filter and oil replacement with Kubota SUDT (new - left over from my B21) recently and now when hot it has the hydro whine but also sounds like air passing thru the valves - squeals like a pig when under duress - on a hill etc.

When cold there is no squeal/bypass - only when hot it squeals. It still pulls well and doesn't lack power, so its more an annoyance and matter of what is causing this.

Is it the Kubota SUDT being too thin when hot? (SUDT indicates it is a replacement for Hytran Ultra)

Is it air? There is evidence of air bubbles on the dipstick.

Is it the release valve spring on the side of the hydro being weak?

Does anyone else run SUDT in their Sundstrand hydro (17/18xx, X82 vintage)?

Or should I just get better ear plugs?

One last question - usually I drain the oil by loosening the rear pan seal bolts and then regasketing - does anyone use the drain plug in the front behind the hydro - looks like a freeze plug? This would save time if that plug is meant to be removable..

Thanks in advance. Carl

 

[RickB]

I guess if it was relatively quiet for that many hours and now it is hollering at you with different oil it's time to drain it out and go back to HyTran.

The real question is, do you want to buy a new batch of oil and a filter, or replace the tractor or its transmission. That's what you are risking here.

 

[Carl_NH]

Rick,

Kubota SUDT is a replacement to the Hytran Ultra, and no, no issue in going back to the Hytran fluid. I have the detailed SUDT specs, unfortunnately Hytran Ultra detailed specs are limited to what "Viscosity Oils" provides. The SUDT specs clearly state it is compatible/compliant with Hytran Ultra.

I just wanted to hear if 1) other have used SUDT in these units with success/issues, and 2) if the plug behind the hydro unit is removable - if so this simpllfies the R&R of the fluids and 3) if the release valve is weak in the hydro as the potential cause of the squeal.

Thanks

 

[RickB]

There's a thread in the buying/pricing forum titled "Bad oil New Tractor" you need to read. The premise is a little different, but the message is the same. You are getting different feedback from your Sunstrand unit and your SUDT jug. Which should you believe? Information from other folks is valuable, but should not supercede what your equipment is telling you. If you were having no relief valve symptoms before your oil change, you don't have a problem in that area now. I can't help you with your drain plug question, but I'd be putting Hytran back in that unit before i mowed again if I were you.