The GST Transmission

[SetterDog]

I recently purchased a Kubota with a GST transmission at an auction and really trying to understand it. Some of my questions are......... Is it totally 100% gear driven? Does it use the hydraulic pump in any way in regards to the transmission? On a Kubota with GST what other parts use the hydraulic pump? The steering? If the hydraulics are not being used to drive the tractor can I attach and run hydraulic motors without starving my transmission / tractor for fluid/pressure. Is the hydraulic fluid used as gear oil? If I am using the hydraulics to do something and the fluid gets hot, will it cause damage to the transmission even though it is gear driven?

I appreciate the input. I know there is a lot of differing opinions on the GST transmission in relationship to the HST. I'm really not to interested in those. I'm more into understanding the GST transmission.

 

[loggin]

I recently purchased a Kubota with a GST transmission at an auction and really trying to understand it. Some of my questions are......... Is it totally 100% gear driven? Does it use the hydraulic pump in any way in regards to the transmission? On a Kubota with GST what other parts use the hydraulic pump? The steering? If the hydraulics are not being used to drive the tractor can I attach and run hydraulic motors without starving my transmission / tractor for fluid/pressure. Is the hydraulic fluid used as gear oil? If I am using the hydraulics to do something and the fluid gets hot, will it cause damage to the transmission even though it is gear driven?

I appreciate the input. I know there is a lot of differing opinions on the GST transmission in relationship to the HST. I'm really not to interested in those. I'm more into understanding the GST transmission.

It is a gear driven transmission with hydraulic activated wet clutch typically. Most tractors have 2 separate hydraulic pumps, one for steering and one for the rest. Some bigger tractors have 3 pumps. As for running hydraulic motors you would have to match the motor with the flow rate and pressure of your pump. Typically hydraulics and trans fluid are the same. The fluid does not get as hot as with a HST transmission.

Here is a video explaining some things.

Hope this helps!

 

[Fallon]

A GST is just a manual transmission that can be shifted automatically. It doesn't suffer the 15% HP performance penalty of a HST, but doesn't have quite the same ease of use or precision as a HST either. A definite upgrade over a manual clutch.

I prefer a HST personally, but a GST is definitely better than a manual shift machine. GSTs have a reputation for being pretty reliable. The wet clutch lasts a LOT longer than a dry clutch. Generally the clutch pedal operates a dry clutch and the GST levers or shuttle operates the wet clutch. Always use the wet clutch if possible. In the occasional use of a friend's GST machine I never got a good feel for the GST timing & often defaulted to the clutch pedal though. I'm sure more hours would build trust & feel for the shuttle lever over clutch pedal.

Tractors in our class use the transmission as a common hydraulic sump. If you overheat your hydraulics, it doesn't do your transmission any favors. I believe there is a separate pump to run the GST hydraulics, but am not sure. You won't starve your GST though.

 

[rbargeron]

The GST was a pretty sophisticated addition to the compact tractor world - may have been ahead of its time. It was an optional transmission (standard equipment on L35's) where the clutching and shifting of gears is all accomplished hydraulically. When you move the shifter to any one of 8 speeds the trans does the rest. The only one I've driven took a full second to clutch and shift, so going downhill with a load it was good to have a foot ready on the brake pedal until I got used to it.

For pumps, most GST tractors have a single pump on the side of the engine that supplies everything - power steering, GST controller, wet shuttle, 3-point, loader etc. The L35 also has a second front pump on the engine for its backhoe.

To answer your original question, yes the GST is a completely gear-driven tractor - only the clutching and shifting linkagees are hydraulically operated.

As always, prompt cheerful refund if any info is bogus. Dick B

 

[Fallon]

The GST was a pretty sophisticated addition to the compact tractor world - may have been ahead of its time. It was an optional transmission (standard equipment on L35's) where the clutching and shifting of gears is all accomplished hydraulically.

I wouldn't say ahead of its time. Powershift transmissions, usually dual clutch have been around since the 80s or 90s for sure. I was driving dual clutch powershift (18-21 speed, all auto) & power quad (compound tranny 1 manual, 1 powershift) 100-300hp John Deeres in the late 90s. They could upshift while plowing. But if you tapped the clutch to the floor & let it out as fast as you could it would stall the tractor. Boggled my mind how fast & well those machines could shift.

I'm sure there have been various sorts of powershift machines around since the 60s or 70s.

GST is a good economical version for CUT sized machines though. Different performance level & shift speeds than the ag machines, which were way more expensive.