Lengevity and reliability of various transmission types

[dex3361]

I wish I could edit the title. I cant believe I spelled longevity wrong.

I didn't notice till you mentioned it.

 

[TheRegMan]

This is really an interesting and informative thread. I am certainly no expert on trannies but I was trying to understand hydros a couple of weeks ago to try and determine the likelyhood of winding up with very expensive future repairs if I buy another hydro. I found some info on the internet that gave a brief explanation of all different types of tractor transmissions.

People keep using the line, "the more complex it is, the more likely it is to break." I believe that myself however, from what I can tell and what I have read, the hydro is really a simple system essentially comprised of a hi-flow pump and a big hydraulic motor. Now this may be a bit over simplified a bit but from what I can find, that's essentially what it is. Push the treadle peddle forward and the fluid pumps in one direction causing appropriate movement of the tractor. Push the treadle the other way and the fluid reverses with reverse movement.

Out of all the trannie descriptions I read, this did seem like the most simple technology of them all. No clutches or gears to break.

Maybe the old line "the more complex it is, the more likely it is to break" is in fact true. Maybe that is why everyone is commenting on hydros having no real history of failure.

Is it possibly the simpleist of all?

Please don't interpret my comment as me putting out garbage when I really don't know what I am talking about. I have read this thread with great interest trying to learn as the OP was hoping to do. I put the thoughts out to draw information from those of you that have real knowledge on the subject matter.

Thanks

 

[Specop_007]

Reg I think for me the point is with geared transmission used properly its just almost impossible to break them. The wear point on the transmission is the clutch. If you dont ride the clutch, theres almost no way to damage a geared transmission.

With hydrostats theres more maintenance involved. While in design the unit may have less parts the interaction of those parts has a higher degree of failure IF the maintenance intervals are not observed. With an "old fashioned" gear unit there is no maintenance.

So from strictly a number of parts observation it may be true that a gear unit has more parts but from a reliability over time with minimal maintenance I think the gear unit comes out ahead of the hydro.

But if someone is good with maintenance and doesnt mind that cost over time I suppose that may change the playing field.

 

[dfkrug]

Out of all the trannie descriptions I read, this did seem like the most simple technology of them all. No clutches or gears to break.

Maybe the old line "the more complex it is, the more likely it is to break" is in fact true. Maybe that is why everyone is commenting on hydros having no real history of failure.

HST units are clearly more complex than simple crashbox-type gear trannies.
As I noted earlier, both HST tractors I rebuilt had failed drivelines, one in
the range shift gearbox, the other has a broken wet PTO clutch. HST
tractors still have clutches and gearboxes. (It is interesting to note that
skidsteers have no gearboxes or clutches, and their HSTs drive chains and
sprockets. THOSE setups are indeed simpler.) Then there are the semi-
auto type tractor gearboxes, with multiple wet clutches and hydraulic
actuation. I have yet to open up a Glide Shift Trans, but I would like to. I
suspect that it will have similar complexity to the HST units I have
been into.

As to complex systems being more failure-prone or maintenance-intensive,
that does not fly either. Our cars are much more complex, but are also
much less failure-prone or maintenance-intensive. Gone are "tune-ups" and
the electronics help out a lot with built-in diagnostics. Much better in a lot
of ways, versus old iron. Even the old-fashioned dry foot clutches in
modern cars are much better than in the old days...all 3 of my vehicles have
them.

 

[mostly_gas]

something no one has mentioned on gear trannies that if no syncromesh on the gears then the possibility of breaking gears is very real. I forgot to tell the wife not to shift the old 8N and the trannie was in 2 gears at once according to the shop that repaired it. When i got my Ford 1700 and had the front axle rebuilt, the dealer reminded us not shift on the fly as that could ruin the trannie or the front axle.

 

[Chilly807]

You've got a point there. Kubota puts a big ol' sticker on the dash reminding us NOT to shift on the fly, or even while there's any motion at all. They've got a point too, every time I do it it grinds away. I never shift on the fly, but occasionally things are still moving a touch.

If you're sitting still for a few minutes, idling in neutral, then go to engage a gear it'll usually want to grind as well. One thing I've found that helps a lot in that dept. is to give the throttle a tap, and engage the gear as the rpm is coming back down. Seems to work for me.

Chilly

 

[Soundguy]

something no one has mentioned on gear trannies that if no syncromesh on the gears then the possibility of breaking gears is very real. I forgot to tell the wife not to shift the old 8N and the trannie was in 2 gears at once according to the shop that repaired it. When i got my Ford 1700 and had the front axle rebuilt, the dealer reminded us not shift on the fly as that could ruin the trannie or the front axle.

Having an old N in 2 gears at once isn't a synchro issue.. it's a worn shifter nub / shift pattern issue.. ie.. notr shifting the other gear out when you then select another.

soundguy

 

[N80]

I bought a plain old gear drive (Kubota L4400) for several reasons. First, it was what I could afford. Second, I assumed it would be more reliable than more complex transmissions over time. This may or may not be true. But I think it is pretty clear that gear drives can, have and should last a long time. But, the third reason is simplicity itself and is the reason that now, even if I had more to spend, I'll still get a basic gear drive. Its not just a simple appeal of simplicity. The appeal is that a mile down the road from my place I have access to a pretty full tractor repair shop on my neighbor's farm.

And while he and I could easily split the tractor and change the clutch and he could do most any work on the tranny, neither of us have the expertise to even touch an HST.

So my fondness of the basic gear drive has a lot to do with the fact that I could make basic repairs (with his help) without the need of specialized shops, mechanics, tools or parts. And that is very appealing to me.

 

[RobertN]

Not sure what you mean. I had a Kubota with HST for 12 years.

Every couple hundred hours or so, it got an oil change and a filter.

Old fashioned gear tractors have recommendations for fluid/oil changes too. So you don't have a $10 filter on the system... They still have a recommendations for hydraulic(ie loader ect) fluid change too. On my Kubota, the hydraulics were all on one system. So, one fluid change.

What maintenance are you referring to?

One thing I would note, is after 12 years of being here(was here before the date in my signature; everything defaulted after a upgrade on TBN back in 2000), I hardly ever have heard of issues with either type tranny. Heard a whole lot of speculation, but not many tranny issues.

With hydrostats theres more maintenance involved. While in design the unit may have less parts the interaction of those parts has a higher degree of failure IF the maintenance intervals are not observed. With an "old fashioned" gear unit there is no maintenance.

 

[Specop_007]

Not sure what you mean. I had a Kubota with HST for 12 years.

Every couple hundred hours or so, it got an oil change and a filter.

Old fashioned gear tractors have recommendations for fluid/oil changes too. So you don't have a $10 filter on the system... They still have a recommendations for hydraulic(ie loader ect) fluid change too. On my Kubota, the hydraulics were all on one system. So, one fluid change.

What maintenance are you referring to?

One thing I would note, is after 12 years of being here(was here before the date in my signature; everything defaulted after a upgrade on TBN back in 2000), I hardly ever have heard of issues with either type tranny. Heard a whole lot of speculation, but not many tranny issues.

Maintenance being changing the fluid and filter. While obviously its recommended to follow all maintenance intervals for ones tractor I'd put good money that if you bought 2 identical tractors except one with gear and one with HST then proceeded to run them for 5 hours a day and never do any maintenance on the transmission there would come a time the geared tractor would be pulling the HST home and then go on to pull double duty for the next 20 years.