Nasty Little Hydrostatic Transmission Secrets...

jinman · Mar 1, 2004

Rick, in all fairness, I checked the advertised final drive speeds for all Class III tractors and they are the same. On your suggestion, I checked the transmission gears for the HST and they are the same also. When I checked the rear axle and differential, the TC35 and TC35D have different part numbers for the differential case, pinion shaft, and some gears. I'm certainly interested to know if these gears provide a different gear ratio or if they are just more heavy duty parts for the 40 and 45. At any rate, the parts for the 40 and 45 are identical, so I might have to revise my original assertion upwards to just include those two larger Class IIIs.

Please let us know what you find out. /forums/images/graemlins/smile.gif

LAGEORGE · Mar 1, 2004

Brad, when I go light on the throttle I am not getting all the horse power to the wheels unless I put my foot into it. I have been able to get the tractor to lug down pretty far before I get forward motion. When doing this I get smoke and really get to hear that engine strive to stay alive. It is kind of cool and is one thing that New Holland advertising was correct in stating.
So let me clarify I have never had a relief valve keep me from going forward, in fact I can continue to the point it will always stall. But I cannot say that about reverse movements, those are very frustrating since that damm valve keeps me from getting the work done. To me it sounds like you are having a problem with the relief valve going forward since we all know the reverse one is normal, so I am told.

George

paccorti · Mar 1, 2004

Jinman,

It's funny that you mentioned all of this as I wrote this up about 3 years ago but the posts seem to be lost in time...

What I'd really like to know is what is the HST relief pressure of a Kubota L series and a JD 4*** series? That would tell us a lot. Anybody know?

Peter

BigDave · Mar 1, 2004

( I agree! But it seems that NH has a tractor that is designed just the opposite. It's transmission is meant for the lowest horsepower in a class and the larger hp ratings are protected/limited by the relief valve. That's the frustration. )

Let me get this straight, the relief valve on your hydro is designed to prevent damage to the tractor and the engine? Could it be that you get more HP to drive the implements, but the hydro is designed to protect the tractor's chassis. I have the TC33D of which I've spun the rear tires on many occassion, but I also hit the transmission limits while attempting to pull a 3' diameter by 25' tree trunk. The tires torqued so much I was fearful that they would come off the rims. Now maybe if the tranny was less safe, I could have done some damage to my tractor or stalled the engine. Stalling your engine while under load will shorten your tractor's life far quicker than popping a relief valve regularly. I actually think it is a good thing that the hydro provides this safety factor. If I had a gear shift, I probably would have broken a major component by now, but that's just me. /forums/images/graemlins/wink.gif /forums/images/graemlins/grin.gif

RHP · Mar 2, 2004

New guy! I've been a vicarious learner here (lurker) for quite some time. Last month I became the proud owner of a 2002 TC35D somewhat unexpectedly. (Deal of a lifetime, maybe that will be another post). Last night I was reading and learning more about my machine here and I was concerned that I made a bad decision on the HST transmission. Today my faith was renewed. I deliberately tried to push immoveable boulders and stumps and all three wheels were driving hard as expected. The rear diff was locked and one front was churning. Frankly, I couldn't ask for more. This was on established, well sodded ground that I'm clearing with the help of a trackhoe. I went through deep, wet ditches that would have stopped my 8n cold, causing me to use the 8n loader to push myself out of a fix. I am thouroughly happy with this machine, but let me add a caveat. I have noticed the HST giving out when climbing a hill in the wrong (high range) gear. It did stop (whats going on???) when I had a box blade full of gravel going uphill on a road in high range. I'm learning, it was a natural response to push the pedal harder to try to get more power. I've learned, less is more.

All of the owners here who share their experiences are appreciated. Thank you. Lift up my hood and you will see Mike "PineRidge's" battery set up and welding project. Jinman Jim gave me the knowledge to go to the dealer and point out the acid corroded parts that needed replacement. So many of you have valuable advice.

I've been a little concerned about the HST but today I'm happy again. I'll tell you, the bit of brush hogging I've done with this machine has been amazing.....my much loved, now sold 8n would not hold a candle to this 35D!! Stall it out by working it so hard? I did it a million times, a stall out is not always the best resolution! Hard on clutches because you learn to start slippin' them to not stall!

Love this 35D!! /forums/images/graemlins/wink.gif /forums/images/graemlins/wink.gif

HST is very appreciated! /forums/images/graemlins/grin.gif

have_blue · Mar 2, 2004

( I agree! But it seems that NH has a tractor that is designed just the opposite. It's transmission is meant for the lowest horsepower in a class and the larger hp ratings are protected/limited by the relief valve. That's the frustration. )

Hi Jim,

Having been involved in manufacturing and engineering, this whole thing came as no surprise to me. Having the manual shifter, I wonder if all tractors within a class have the same transmissions and (even scarier) clutches. Being at the lower end of the class, my TC35 clutch should hold up better than a TC45 if they do indeed have the same clutch. In fact, the TC35 _should_ be bullet proof.

Someone gave a great analogy about the bush hog gear box. I had a 5 foot box, and traded up on a 6 footer of the same brand. Well, the gear box looks identical. Was the box designed for a 5' deck and "stretched", or designed for a 6' deck and overbuilt for a 5 footer? We just don't know, do we? /forums/images/graemlins/smile.gif

If I had to guess, I would think NH did their homework. I don't think we should lose any sleep over our equipment as long as it works great.

jinman · Mar 2, 2004

( It's transmission is meant for the lowest horsepower in a class and the larger hp ratings are protected/limited by the relief valve. )

( Let me get this straight, the relief valve on your hydro is designed to prevent damage to the tractor and the engine? )

Big_Dave, I've reread my sentence a few times and I realize I could have done a far better job of expressing what I meant. I meant that the transmission is protected from the greater horsepower rather than the tractor itself. Surely the tractor can handle anything the hydro throws at it because it can handle a manual transmission, and that's going to provide more shock load to parts than any hydro tranny.

The point I'm making about the transmission is that the transmission has relief valves that open at 5,000 psi. It doesn't matter if it's a TC35D or a TC45D. That extra 10 horsepower does not get you a higher pressure relief valve. That's all I'm trying to say. Whether that relief pressure was designed for the larger hp as Don suggested or for the lower hp as I suggested, it's still the same throughout the entire range of the Class IIIs. There is not another NH class of tractors that has a single hydro transmission for that great a range input horsepowers. I think that's worth noting, even if it's only tractor trivia. /forums/images/graemlins/smile.gif

jinman · Mar 2, 2004

( I've been a little concerned about the HST but today I'm happy again. )

Thank goodness! /forums/images/graemlins/grin.gif I'm going to say one more time that I am THRILLED with my tractor. It could do some better in some situations, but this not a major detractor from what is a great little tractor. It's just something that stirikes me as an interesting point. I'm glad you like your TC35D. The hydrostatic transmission and the layout of our tractors allows us to do far more work than you could ever do with your 8N or I could do with my old Ford Jubilee.

( I have noticed the HST giving out when climbing a hill in the wrong (high range) gear. It did stop (whats going on???) when I had a box blade full of gravel going uphill on a road in high range. I'm learning, it was a natural response to push the pedal harder to try to get more power. I've learned, less is more.
)

Now let me play "the devil's advocate" and ask you a question. When your tractor stopped on the hill, If I came up behind you on a TC45D and I stopped in exactly the same place, wouldn't you be surprised? I think I would. I might not even be able to get as high as you because my tractor is heavier and my relief valve might pop a few feet down the hill. /forums/images/graemlins/blush.gif Do you see why I find this a curious fact? /forums/images/graemlins/crazy.gif

jinman · Mar 2, 2004

( Being at the lower end of the class, my TC35 clutch should hold up better than a TC45 if they do indeed have the same clutch. In fact, the TC35 _should_ be bullet proof. )

I'm one of those people who is "dangerous" with a parts manual in my hands. /forums/images/graemlins/shocked.gif /forums/images/graemlins/laugh.gif

Here is what I found: The clutch on the TC35 and TC40 is the same. The clutch and pressure plate on a TC45 is different. I didn't check other parts, but I think you can be sure that for a manual transmission, the higher hp rates "beefier" components. /forums/images/graemlins/cool.gif

byax65 · Mar 2, 2004

Jinman,

You must be retired? /forums/images/graemlins/grin.gif Or a pilot.. /forums/images/graemlins/smirk.gif /forums/images/graemlins/laugh.gif

BYax