Yanmar YT3 series (YT347/YT359) IHMT/I-HMT Transmission workings

[troverman]

John Deere loves their 3-cylinder turbos. Kubota engines are all 4-cylinder turbos, if they are so equipped. I don't think there are reliability issues with turbos, but I prefer a 4 cylinder over a 3 cylinder any day of the week. It simply is a smoother engine.

 

[normanb]

The Yanmar's ability to generate less heat under heavy loads may be true, but I guess I'm not seeing HST transmissions blowing up doing the same work...so is it really an advantage?

So I "subsoil" my pastures on off years before doing other work with them using a rino two shank 3pt ripper. I pull it at about a 20inch depth. I tried that with a rented HST and the heat was an issue when doing a couple of acres. The I-HMT was the main reason I got the Yanmar over the Grand L6060. I have also plowed and turned them as part of the reclaiming process.

I have also seen heat issues on HSTs when running a heavy flail or brush hogs on a hot day with heavy foliage.

The heat issue really mainly impacts equipment life and operating range.

Now, depending on your use cases and workloads nothing above may apply.

In the end, I just prefer the flexibility and usability of the IHMT with the A/B mode over any HST or GST I have tried from Deere, Case, or Kubota

Chris

 

[troverman]

I run flail mowers on my tractors through very heavy grass for hours on end, and all of it is done on slopes. I mow capped landfills and drinking water reservoirs. I've had very good luck with my HSTs not overheating, I guess.

With an HST, there will be an additional cooler up front and if it is blocked with dust / dirt / chaff, or if any of the coolers behind it are blocked, than your hydraulic fluid will not cool effectively.

There's basically nothing to wear out in an HST, so short of running the hydraulic oil out of it, it won't wear out. Kubota's latest gen of Super UDT-2 synthetic fluid ships in all the machines now and works exceptionally well at both high and low temps.

Again, I think the Yanmar trans is pretty cool but I'm not sure it has real-life advantages over a quality HST.

 

[eekbin]

In Yanmar's literature, I see two different PTO ratings - "at zero speed" and "at working speed." What's that all about?

Yanmar, if you are watching this forum, you should have answered this. Troverman, I'm not sure if I have a totally complete answer for you, but I'll give it a shot. Take a look at different, roughly 60hp tractors. 60HP HSTs loose about ~10hp between the rated engine HP and rated PTO HP. Now take the equivalent gear tractor of the same size. It will loose only about ~7HP between rated engine and rated PTO HP. What Yanmar is showing here is that indeed the YT359 looses a similar 10HP to the PTO at a stand still, yet when you get to rated speed (Zero pumping speed, per my my initial explanation that began this thread), You are only loosing 7HP. The point is, at rated speed, the IHMT behaves similar to a gear tractor, so you get less losses at rated speed due to more of a direct connection from the engine to the PTO and wheels. This would be an advantage not to equipment used at a stand still, but instead PTO powered equipment that is operational while the tractor is moving. When not moving, it would be comparable to other 60HP tractor PTO losses.

 

[troverman]

Thanks eekbin. That makes sense. Somebody like myself that runs a flail mower would see an advantage here over HST. I've used the Kubota Glide Shift (GST Trans) which is essentially a gear drive with an automated clutch and noticed it lost less horsepower running a flail compared to a same HP HST.

 

[ArthurHA]

I found the Transmission easy to get use to, I like the "brake" effect of taking your foot off the accelerator peddle, for lack of a better name for it. I was told the transmission has been around for over 12 years, and the tractor is bulletproof.

 

[mancini0]

Has the tractor continued to be good for you? Does it still have three mechanical ranges like a traditional HST?

Aside from heat buildup and possible efficiency advantages, I still think a standard HST is more productive, since shuttle action is never required. Particularly the Grand L Kubota which is the same size as this tractor and has hydro-dual speed.

The traditional HST still has a shuttle action - it's the act of pressing the tredal pedal backwards or pressing a separate pedal. Since the shuttle on the i-hmt is just an electrical signal indicating which way the pump should pump, it seems Yanmar could have also hidden this functionality in a reverser pedal to mimick a traditional HST's operation.

 

[freightboy]

The traditional HST still has a shuttle action - it's the act of pressing the tredal pedal backwards or pressing a separate pedal. Since the shuttle on the i-hmt is just an electrical signal indicating which way the pump should pump, it seems Yanmar could have also hidden this functionality in a reverser pedal to mimick a traditional HST's operation.

That isn't at all how the I-HMT works. The reverser lever controls forward and reverse by controlling 3 solenoids that control the forward and reverse clutch as well as the clutch pedal. You don't have to let off of the pedal to change direction, the YT3 will change direction with varying speed based upon how the motion control dial is set. The change takes a bit to get used to, but it is a vast improvement and can change directions for loader work much faster than a traditional HST.

 

[Williy]

From what I have been told that transmission on the YT359 iis
like have two transmissions in on the hydro converts to standard
transmission. The hydro makes is easy to use and then going
to standard is like a regular standard transmission tractor
Its clear as mud

willy

 

[Yander]

I run flail mowers on my tractors through very heavy grass for hours on end, and all of it is done on slopes. I mow capped landfills and drinking water reservoirs. I've had very good luck with my HSTs not overheating, I guess.

With an HST, there will be an additional cooler up front and if it is blocked with dust / dirt / chaff, or if any of the coolers behind it are blocked, than your hydraulic fluid will not cool effectively.

There's basically nothing to wear out in an HST, so short of running the hydraulic oil out of it, it won't wear out. Kubota's latest gen of Super UDT-2 synthetic fluid ships in all the machines now and works exceptionally well at both high and low temps.

Again, I think the Yanmar trans is pretty cool but I'm not sure it has real-life advantages over a quality HST.

Normanb just posted a real life advantage. You cannot even begin to compare running a flail mower on a hydro to that of pulling a sub-soiler. I say, there is your real life advantage, choose to ignore it if you like.

You need to stop trying to compare the Kubota Hydro to the Yanmar's I-HMT. Saying it several posts in a row, don't make it so bro.