Lengevity and reliability of various transmission types

[DK35vince]

A big rotary mower will act as a large flywheel and continue to "drive" the my tractor through the PTO. Creeps me out sometimes.

I find it hard to beleive that a JD 770 does not have some type of internal overrun clutch for the PTO to prevent that from happening.
Even my older 1978 JD 850 with single stage clutch and non-live PTO has an overrun clutch so a brush mower doesn't drive through the PTO pushing the tractor.

 

[oldnslo]

A lot depends on the style of hydro stat transmission used.

Most of the smaller lawn tractors and lots of the Zero turn mowers use throw away units that do not like hard pulling for extended periods of time. Not positive what these units are called. I call them cam and ball hydros since ball are driven by cams which transmit the torque

Heavier duty machines like compact tractors typically use swashplate/ piston style hydro statics. These have a swash plate which pivots on bearings and the pistons follow the swashplate and fluid is forced out which does the work. Keep these systems clean and cool and they will for hundreds or thousands of hours.

Two main draw back of hydrostatics are:

They get hot when used hard for extended periods of time.

Typically 90 - 95% efficient so some HP lost. Not sure how this compares to Gear trannies of the same size.

NOTE: IH made some hydro farm tractors in the 50 HP range back in the mid 70's.

Roy

 

[Chilly807]

A lot depends on the style of hydro stat transmission used.

Most of the smaller lawn tractors and lots of the Zero turn mowers use throw away units that do not like hard pulling for extended periods of time. Not positive what these units are called. I call them cam and ball hydros since ball are driven by cams which transmit the torque

Heavier duty machines like compact tractors typically use swashplate/ piston style hydro statics. These have a swash plate which pivots on bearings and the pistons follow the swashplate and fluid is forced out which does the work. Keep these systems clean and cool and they will for hundreds or thousands of hours.

Two main draw back of hydrostatics are:

They get hot when used hard for extended periods of time.

Typically 90 - 95% efficient so some HP lost. Not sure how this compares to Gear trannies of the same size.

NOTE: IH made some hydro farm tractors in the 50 HP range back in the mid 70's.

Roy

The HST version of my tractor has 1.5 less advertised PTO HP than the gear model, so it's not a lot lost.

Chilly

 

[Hoosier Hay Man]

You don't see HSTs in large wheeled tractors, probaly
because they are for continuous AG-type work. (I am not a farmer, but
I do see these big tractors at the shows and ask a lot of questions.)

IH built large AG tractors and utiliities tractors (for their day) that were Hyrdros back in the 70's and early 80's. They never caught on big in large AG tractors, but some are still working ground today. Combines have used Hydro technolgy for the last 30+ years. I wouldn't be scared of any style of tranny as long as it is maintained. I have a 1466 with a T/A and it works well and a John Deere Quad Range that I like alot also. They are both over 30 years old and still going. Hydro has been around for quite awhile now. Probally the only new technolgy in transmissions is the IVT, Infinte Varible Transmission. It isn't seen in utilities or CUT's yet as the Hydro does the trick and is much less expensive. An IVT has gears but somehow eliminates the power jump you get in a power shift when shifting on the go and still acts like an hydro. It also has a computor to match RPM's and ground speeds to save fuel and maximize draw bar HP.

Both power shuttle and hydro have been around a long time and will give you good service life if properly maitained.

Good Luck!!!

 

[SABULA FARMER]

A gear box I think is best. Hydro's are good, but I think you will have less problems with a standard gearbox. Less money in the long run also, I have a gear drive unit and love it. I didnt want the extra burden of costly oil changes, filters and heat build up.
Then again I do more than wash and wax my tractor....I run a 12in two bottom plow, 6' discs, 5' brush hog, 7' back blade and have never doubted my purchase. But the real question is what do you want...?

 

[Soundguy]

Not all is "peaches and cream" on the gear shift side in my eyes.

My machine has a collar shift (like the 790) and dual stage clutch. Pretty nice, but I can feel the wear in the drive clutch verses the PTO clutch. The result is an increasingly difficult to shift PTO. Now I still have quite a bit of adjustment left, which I assume (have not visually inspected the clutch) I have at least some clutch lining left on the drive clutch. If I decide to keep running it the way it is, eventually I have to decide if I want the PTO always turning or allow the clutch to start to slip. Fortunately it only sees on average about 25 hrs per year, but eventually, I'll be splitting the tractor.
Just my 2 cents.

that's not a trans problem.. that's a maintenance issue.

if the brakes in my truck need replacing I shouldn't complain that they don't last forever.. they are a WEAR item designed to be replaced. when they need it.. do it.

also.. IMHO.. clutch life is directly related to operator experience, with also a good portion based on type of work done.. I expect loader tractors with clutches to have them wear out faster.. etc..

soundguy

 

[RoyJackson]

I find it hard to beleive that a JD 770 does not have some type of internal overrun clutch for the PTO to prevent that from happening.Even my older 1978 JD 850 with single stage clutch and non-live PTO has an overrun clutch so a brush mower doesn't drive through the PTO pushing the tractor.

I also find this odd... My old 670 (770's smaller brother) had an over-running clutch. My 60" cutter never pushed the tractor. I suspect crashz isn't pushing his clutch down far enough or the clutch is adjusted incorrectly (especially after reading the rest of his post).

 

[JB4310]

I know OP is about comparing CUT trannys but as far as longevity and reliability in general ...
Aren't HST in every piece of off road heavy equipment made? never seen a clutch in the big wheeled loaders etc. I know some are just shuttle shifts, but haven't HST been around a long time in heavy equipment?

Wonder what the percentage of HST vs gear in the under 50 HP tractor range being sold is, maybe 60-70% hydro? or more, especially with every machine coming with a loader these days.

JB.

 

[jenkinsph]

Soundguy,
Here is a perfect example of the perception that hydros are bound to have more problems than gear tractors.

What I find humorous about this is the fact that all of us older hydro guys grew up with gear tractors (I still have my 820 in very good condition) but I find few of the gear guys have had and owned a hydro tractor as I have for 5 years or better.

A gear box I think is best. Hydro's are good, but I think you will have less problems with a standard gearbox. Less money in the long run also, I have a gear drive unit and love it. I didnt want the extra burden of costly oil changes, filters and heat build up.
Then again I do more than wash and wax my tractor....I run a 12in two bottom plow, 6' discs, 5' brush hog, 7' back blade and have never doubted my purchase. But the real question is what do you want...?

 

[Redneck in training]

When considering pulling power of HST versus gear trany you have to consider also mass of the tractor. We have 33HP HST (TYM 330) and I run out of traction before I run out of power. So in such a case the trany type doesn't mater.
I selected HST after talking to a guy who repairs tractors and fork lifts. HST gets abused in fork lifts and he said that they oulast any gear as long as the fluid is changed and kept clean.
Speaking about HST and torque converter (hydrodynamic tranny) difference: HST uses variable delivery pump and constant displacement hydro motor or constant delivery pump and adjustable motor. The pump and the motor are connected by piping.
Torque converter uses constant delivery turbine pump and hydraulic turbine. The torque is changed by adjustable giude vanes between the pump and the turbine. Both types of hydro tranies generate heat but modern hydrodynamic torque converters have a lock that locks the pump and the turbine together preventig slippage and thus heat generation. Both the pump and the turbine are mounted in close proximity in the converter housing.