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.

that would make things easier for me, LOL. now to see if I can talk him into it!

The way you're wording your post I'm not sure you understand the reduction on both tractors.

The F-cubs do not have a gear reduction before the trans like the Cub Cadets do (7:1 for the gear drives). The extra reduction is in the axles. The hydro Cubs have a similar reduction between the hydro and the pinion shaft. I imagine the gear ratios in the F-cub trans are probably about the same as those in the Cub Cadet. The drive ratio on the hydro is probably close to 1, the speed of the output cylinder block is probably 85% or so of the pump block at 3600 rpm. So just to clarify, just putting F-cub wheels on a CC with no other changes will increase the speed by about 60%. The F-cub final drives are probably in the neighborhood of 4:1 or something like that based on the numbers you posted, which, if added to a CC rear, would cut the speed down to 2 mph or less.

The F-Cub actually has less power than most Cub Cadets. The F-cub only had 8 or 9 drawbar hp, and only the numbered Lo-Boys had 15-18 hp. There is less stress on the trans itself on those because the engine is a smooth 4 cylinder engine directly coupled to the transmission. The gear reduction in front of the trans on the CC rear means that the transmission internals are experiencing higher torque loads than the F-cub because the reduction is before the trans and not after it. It's also harder on the rear because of the torque impulses of the single-cylinder engine.

I understand the gear reductions completely on both machines, And the point was that they both are probably about the same final ratio at the wheel. This is purely guessing because I could not find any info on it. In addition the f-cubs are gear drives and the 3rd gear is 1:1 that = 6.5 mph at full throttle on 28 inch tires. The cub cadets hydro pump is going to drive the output at at least 15% less rpm than the input. Then it will be reduced again at what you say is probably 7:1 in the reduction housing. Then if he uses the bull gears it will be reduced again at least 4:1 before it gets to the wheels.

So the way I see it the f-cubs engine rpms are being reduced in this order, engine at 1800 rpms, through the tranny at 1:1,then through the ring and pinion into the bull gears at 4:1 then to the wheel

The cub cadet with hydro and bull gears, engine at 4000 rpms into the hydro reduced by a minimum of 15%,then to the reduction housing at an 7:1 reduction, then to the ring and pinion, then to the bull gears for another 4:1 reduction then to the wheels.

A person does not need to know the exact numbers to see that the cub with bull gears added will have allot more (end point) reduction then the f-cub has.

I agree with the 60% increase in speed by adding the 28 inch wheels with no other modification. But the OP said he plans on using the bull gears, so that would reduce everything 4:1 give or take.

And I would have to say that any torque pulses made from the engine would be absorbed in the transition of drive shaft power to fluid power and back to shaft power in the hydro.

I do not intend to make an argument out of this, The addition of the f-cub bull gears to the hydro cub is the key point to this having any chance of working.

f-cub bull gears are around 6.8:1 F-cub and F-cub loboy and loboy 154 and cub cadet all have the same gearsets in the main tranny With there being different 2nd gears depending on the years. all the above have the same carrier and differential gears. Cub cadet has a 7:1 reduction in the front. cub cub loboys have on reduction in the front of the trans.

I will try to get some pics of my project up and maybe some numbers. a hydro with bull gears definately too slow. As for your dads tractor I would say you might get away with a 30 or 31" tire if you were not going to use it as a worker. Parades and shows even mowing I think you would be ok.

well the problem is that knowing him like I do, there is no telling what he would use it for, he just got a zero turn mower, so I know he wouldn't mow with it. and the problem for me is if I built it and it breaks, then I have go in and redo it, I would like to build him something that would last.