Oil & Fuel Sorry but yet another UDT vs SUDT post

kkcomp · Dec 13, 2014

I have seen many posts about this topic and just wanted to share my experiences. I have a Kubota B3300SU with the typical LA504 FEL with a 5ft bucket, 5 Ft brush cutter, 5 ft box blade and the best toy the BH77 Backhoe. Everything was brand spanking new when I got it on purchase the dealer filled all of the Hydro with SUDT and the tractor was great. At the 50 and 100 hr I used the SUDT and all was still fine. I used the tractor to clear 4 acres to make an orchard. I was using the tractor so much that the maintenance was getting too costly so at the 200 & 300 hr I decided to go with straight UDT. After reading the post here I decided I could put up with a little whine as long as I was getting work done. The whine was not the only thing I noticed was different. When I used the backhoe it seemed to be jerky and as the oil warmed up the power seemed to fade away. At first I figured it was just a pressure issue and got the gauges and tested and all was in spec just like the factory said. Well the 400 hr came up so I went to get fluid at the dealer and they were out of UDT and SUDT so I had to make the jump to SUDT2.

Here is where the change comes in. As soon as I put the SUDT2 in and started up the whine was gone as expected even with it cold. The real difference was the backhoe now runs smooth, no jerking no bouncing no noise. The first stump I dug out was smooth and easy and the digging was great. In the past I would have to chew the bigger roots up to break them off. Now the bucket will bust roots without even stopping. What did I learn? The few dollars saved for UDT cost me way more than that in lost productivity. So at least for my particular tractor the 20 bucks for the SUDT2 is the best and only way to go.

DT86 · Dec 13, 2014

Are you changing the fluid every 100h?

BAP · Dec 13, 2014

Why are you changing the hydraulic fluid every 100 hours? Aren't you following the maintenance guid in the owners manual?

s219 · Dec 13, 2014

In reality, the cost problems are due to changing the fluid too often. For the recent model Kubotas I have owned, the hydraulic fluid is not supposed to be replaced until 400 hrs. Only filters are done at 50 hrs, and then at 200,400,600, etc.

Hydraulic fluid is not like engine oil that is picking up remnants of combustion byproducts from cylinder walls and getting contaminated. It should last a long time. Finding iron filings and gray sludge in filters and on magnetic rings is normal, and doesn't mean the fluid is bad (it means the filters and magnets are doing their jobs). Really, the worst thing would be water/moisture, which would be easy to spot during maintenance checks, in which case you should track down the cause of that as the main priority before changing the fluid.

I agree that SUDT has been quieter, based on many posting here on TBN. HST pumps/motors form a fairly complex fluid machinery system, and any slight improvement in the working fluid can be noticeable in terms of noise and motor/pump behavior.

The issues you noted with your backhoe almost sound like air in the system to me. While UDT isn't as good as SUDT (and SUDT2) from a technical specs standpoint, I don't think it would be a root cause of dramatic reduced hydraulic performance. Many of us have operated hydraulics for decades with fluids that are far less sophisticated than SUDT, and even UDT!! Yet if you get air in the system, it can make any fluid behave poorly. It doesn't take much.

Bluegill2 · Dec 13, 2014

I like SUDT2 better myself, but will not change it every 100 hours???

murphy1244 · Dec 13, 2014

And Welcome to TBN..:laughing:

mddorange · Dec 13, 2014

:welcome:
From Alabama. I use SUDT2 in the Transmission, FEL and 3pt Hitch portion as that is what came in it and is what is called for by the manual. I use UDT in the front axle since that is what my dealer told me they use when servicing a tractor.

kkcomp · Dec 14, 2014

s219 said:
In reality, the cost problems are due to changing the fluid too often. For the recent model Kubotas I have owned, the hydraulic fluid is not supposed to be replaced until 400 hrs. Only filters are done at 50 hrs, and then at 200,400,600, etc.

Hydraulic fluid is not like engine oil that is picking up remnants of combustion byproducts from cylinder walls and getting contaminated. It should last a long time. Finding iron filings and gray sludge in filters and on magnetic rings is normal, and doesn't mean the fluid is bad (it means the filters and magnets are doing their jobs). Really, the worst thing would be water/moisture, which would be easy to spot during maintenance checks, in which case you should track down the cause of that as the main priority before changing the fluid.

I agree that SUDT has been quieter, based on many posting here on TBN. HST pumps/motors form a fairly complex fluid machinery system, and any slight improvement in the working fluid can be noticeable in terms of noise and motor/pump behavior.

The issues you noted with your backhoe almost sound like air in the system to me. While UDT isn't as good as SUDT (and SUDT2) from a technical specs standpoint, I don't think it would be a root cause of dramatic reduced hydraulic performance. Many of us have operated hydraulics for decades with fluids that are far less sophisticated than SUDT, and even UDT!! Yet if you get air in the system, it can make any fluid behave poorly. It doesn't take much.

Yes I have been changing the fluid every 100 hours. Mostly because I figured the poor performance I was getting was in part because of how the tractor is used. It is often nearly buried in mud and got wet a lot digging the pond. Also there were times that I could smell the oil getting hot and I mean smell while I was operating the backhoe, FEL or even driving. I understand some of you see changing the oil that often as overkill but remember I was trying to correct the poor performance. As for air I could see that if it were occasional or the fluid was low but it was every single time I used it. Guess it wouldn't have hurt to say that this is also the first time I did the maintenance and not the dealer.

s219 · Dec 14, 2014

kkcomp said:
Yes I have been changing the fluid every 100 hours. Mostly because I figured the poor performance I was getting was in part because of how the tractor is used. It is often nearly buried in mud and got wet a lot digging the pond. Also there were times that I could smell the oil getting hot and I mean smell while I was operating the backhoe, FEL or even driving. I understand some of you see changing the oil that often as overkill but remember I was trying to correct the poor performance. As for air I could see that if it were occasional or the fluid was low but it was every single time I used it. Guess it wouldn't have hurt to say that this is also the first time I did the maintenance and not the dealer.

I have noticed on my L3200 that the power steering gets a little weak if I do a lot of intense loader work near max capacity, and that is likely due to the fluid heating up (I can move buckets of material below max capacity all day long and never have an issue). I have heard similar reports of lost performance from overworking the fluid in terms of loaders, backhoes, etc here on TBN. So there certainly is an effect when the fluid gets hot. Everything we know about SUDT(2) versus UDT suggests it should be better, and it sounds like your experience proves this.

I have no idea what my L3200 came filled with (some suggest there is a factory fill of SUDT, others suggest the dealer does it and makes the choice of fluid). I guess I will find out in a couple hundred hours when the first change comes! I did just do the 50 hour service a few weeks ago, and installed rear remote valves. The fluid that leaked out looked very clean and clear. I topped off with SUDT2.