How strong is a hydro transmission
 

I have a project That I'm currently gathering parts for, I'm going to build a Hi-crop cub cadet, I was going to use the hydro transmission with farmall cub bull gears, but with the amount of reduction I'm thinking now it might be better to run a gear drive with overdrive gears, that way the the bull gear reduction will put things closer to an actual farmall cub speeds. But that means I have a hydro trans left over for another project.

so now to my question, would a hydro pull a set of 38 inch tall farmall cub tires without any further gear reduction? and would it hold up to the normal operations of a standard size tire cub. I have 5 parts tractors that have been well abused, and I'm just looking to do something differant with them.

Thanks,
Mike

It isn't designed to run a vehicle with a 38" tire. If you put any sort of load on it, you're probably going to go through axles like crazy and overheat and destroy the hydro since you will have lost a lot of torque by going to the larger tire and it'll have to work harder to do the same amount of work. It'll also being going 13 mph, which will be unsafe with the higher center of gravity you're going to wind up with by doing this.

A couple of thoughts,

I have said (and I truly believe) that the hydro transmissions are pretty-much bullet proof and that the only way to tear one up is to tow/push one without popping the release valves.

That said, when you pull the forward/reverse lever back to center, I fear that the momentum of the huge tires will keep the tractor in motion, if the tractor doesn't stop moving right away, wouldn't that create the same situation as towing/pushing the tractor?

Heat may also become a factor, there are a lot of people who pull a moldboard plow with their hydro's and never have a problem, however hydro's do not make good competition pullers because the fluid can get too hot and become too thin to do it's job. Personally I don't know if moving all the extra parts and weight will cause heat related problems, but I believe it is at least worth considering.

If I'm off base in my thought process someone please correct me, as I'm always looking for more and better information.

Finally, without spending a ton of money, is there a clutch set-up that would hold up to the same abuse if you were to use a gear drive transaxle?

so I guess with a hydro trans it is what it is, and can't be modified to do otherwise?

Let me ask another question, the bottom line that goes from the gear set to the pump, is that a return, or is that where the fluid is pulled from? could a transmission cooler be plumbed into that line? or is my thinking off? the hydro I have is off a 147 it has a place on the top of the pump for a hydraulic lift, could a cooler be put into that line and then returned to the trans?

I never thought about tire momentum, but that would make good sense. I'm not sure about the clutch set up for a gear drive either, I figured a stock clutch might work, but then the weight thing comes back into play doesn't it, would the clutch slip in getting the big rubber moving.

Thanks for the reply's, gives me something to think about. I'll probably have more crazy/dumb questions to ask soon.

Yeah it basically "is what is is." It is being used for what it is designed for. A bigger tractor needs a bigger hydro unit. There aren't any internal modifications you can do to improve it for this. The bottom line is not the return; it's the suction line, so don't put an oil cooler there. If you open up your service manual, there's a great picture that shows how everything works and how the fluid is routed.

I suppose you could put one in where the ports are on the charge pump, but if your pump is actually from a 147, it doesn't have those. The best place to put the cooler would be between the exit of the hydro unit and the transaxle, as that's where the fluid is the highest temperature, but after you study the diagram in the manual you will see why that is impossible.

The pullers put 60+ hp through their modified clutch setups, so I'm sure you could come up with something that would work.

What exactly to you plan on doing with this thing, anyway?

Matt, thanks for the info, the current plan for the hydro trans was to build my dad a garden tractor, something bigger than a cub cadet, but smaller than a farmall cub, something along the size of a farmall cub loboy, My dad is getting older and is having problems climbing on and of his cub and super A, I wanted to do a hydro because he complains one gear is too low and one is two high to pull a disk, which it probably isn't I think he just likes to complain. I wanted to use the hydro in a cub cadet hi crop I am in the process of collecting parts for, but when he found out what the top speed would be, he made the comment that it would be too slow for the parade at the tractor shows, which in turn changed my plans on how I was going to build it. (basicly its for him too)

I have the hydro apart now, so I understand about the impossibility to put a cooler at the exit of the hydro, now that I know where the suction and return are. I thought it was off a 147, maybe not, it has two ports for lines at the top of the pump, I figured it was for a lift of sometype.

again thanks for the info,
Mike

Get him an 1872 or 2072. Problem solved :)

I'm with Matt. Even a 782 would be ideal. I know from good experience with both that the 782 will outperform the Cub Lo-Boys. My 782 has a 50" deck and is quicker than my 67 Lo-Boy with 60" deck. Plus the 782 is very compact, plenty of power, very maneuverable, and relatively inexpensive for what it's capable of.

If you are set on building a bigger tractor, perhaps a Super Garden Tractor hydro rear end? They're at least gear reduced a little bit compared to older rear ends (which I just recently learned myself).

Just a few ideas :bigthink:

I am going to have to disagree with the above concerns. If you were to run those 38 inch tires with out the bull gears, I am sure you would have problems. But with them I don't believe you will. The bull gears are essentially a gear reduction. Could also be looked at as a permanent low range. And the top speed of a cub with the 28 inch tire is 6.5 mph with an engine speed of 1800 rpms in 3rd gear. (http://www.farmallcub.com/cms/index....pacities-specs)

Now, true you would double that engine rpm and also double the ground speed. But I could not find the gear ratio's for the farmall trany. I would have to bet that the 3rd gear ratio is the same or real close to the cub cadets 1:1. The hydro is not stuck in a gear, so you do not have to go 13 mph if you don't want. And I don't know what the drive ratio is on the hydro pump, but it can't be 1:1 it has to less or it would not work. The engine (input) side has to spin faster than the drive (output) side, or else there would be no pumping action to make pressure to drive the drive rotaries.

I don't think axles will be a problem either, as you will probably have to use and modify some farmall cub axles and they handle that size tire and more power with out problems.

I do agree that you would need to take extra caution when changing directions of travel though. It would be best to come to a complete stop before changing direction, to keep the unneeded stress out of the pump.