Hydrostatic with Transaxle Cooler

I have been searching the internet about how to make my '05 GT5000 Hydro faster. I have seen that the reason why we can not put a smaller pulley on the trans is because of heat. If I were to put a tranny cooler on the hydro, can I keep it cool enough to work? I am not thinking super fast. Trying to get to 10 mph with a reliable trans. Let me know your thoughts.

I wish i didnt throw away my old hydro trans or i would test your theory and tell you if it works.

That would have been awesome. I hate to try it and fail.

i mean i wouldnt try it with a hydro. But it might work but again theres always that "what if it doesnt" factor

i dont think it will, i see it like running an engine at a solid 12000 RPM heat doesnt make much difference its still going to kill it

well think about this auto tranys in car have trany coolers or they would blow up it would take some time and effort but i think it would work with the right size cooler and a fan to help when the temp goes up i am gonna try it if i can find a hydro

Most rider hydros dont have external hoses that connect the pump and wheel motor, so there is no place to put in an inline cooler.
The better residential/ commercial mowers have a cooler for the hydraulic fluid.
If you are looking to get 130-150% of stock speed, I dont see the hydro blowing up. I have increased speed on hydros and not had a catastrophic failure. Just dont try to go stupid fast with one. The pump/motor have springs that will not operate properly at higher RPMs.
kinda like floating the lifters on a car motor by over rev-ing. It will also have a pressure relief valve. If it build up too much pressure, it will bypass back to the pump inlet. This will add to the heat issue.
If you do crank one up, make sure to put in fresh oil and you will need to change it more often.

have you thought of making a custom lift and cutting back the axles and running chains from one or both hydro axles to a live axle underneath it and doing getting your speed from the sprocket ratio instead of the pulleys? I can't see anything going wrong because the hydro is running at normal speeds, its just making sure the hydro has enough power for your live axle.

this is a quick idea of what im talking about

That's the idea I had and noone seemed to think one way or the other when I mentioned it. I didn't make a drawing though. I can't think of a thing wrong with doing it that way.

i had a simaler idea but i wasnt sure if it would work so i havent tried it yet.

matthew sidor wrote:

Thats exactly what me and jamus mean! I really don't know how you find all these pictures, almost every idea someone has you'll find someone who's used it! I think that would be the only way you could get more speed out of a hydrostatic without overheating issues.

dude u go on my facebook and u can find almost every lifted mower posted on the internet except one in videos
https://www.facebook.com/media/set/?set=a.127846830610088.19643.100001543144012&type=3

matthew sidor wrote:

dude u go on my facebook and u can find almost every lifted mower posted on the internet except one in videos
https://www.facebook.com/media/set/?set=a.127846830610088.19643.100001543144012&type=3

Yeah that would work if I had Facebook. I hate Facebook, but I guess it's my loss.

Hydros wont take being sped up, my 99 hydro murray already has a 3" pulley on it - and its stock - with a 17HP twin on it, it boogies pretty darn good stock.


Best way to use a straight axle is get a 700R - the kind similar to a right angle gear box - lower input and side sprocket - less stuff to break.

Hey everybody i used to play around with mowers and now im gettin back into it and someone gave me a hydrostatic mower and i want to just change the pulley for a lil bit more speed and torque never done this to a hydrostatic before its gonna be a mud toy any input would be great

Hydros dont like to be modified - youd be better off with a manual trans.

My 17HP twin hydro murray already has stock on it a 3" trans pulley - thats about as small as you can go .

So, Obviously Hydros are useless for speed, But are they "ok" for an off road mower?
I have two mowers with Hydro trans, no budget for the two, so I was thinking they would be "ok" for a trail-off road mower...
I was thinking these might be best for my hunting mower...anyone think differently?

So the set up on both are MTD chassis, hydro trans, and both could have 17hp Kohlers ( or 12.5 briggs, 20hp optwin briggs) (yes i have all these engines)
When I say "Hunting Mower" I use them for durabilty, reliability, and try to reduce noise as much as possible. I also add typical things like rear rack, headlights, and brush guards.

So, with those specs, limited budget, does anyone agree on a hydro being decent enough to keep for that purpose?

As long you realize the limitations, I don,t think you will have any problems making a transport vehicle out of it. It won't have a locked diff, so traction could be an issue, but otherwise I would say do it.

I love my hydro for off road. I have the ability to make it really crawl along. Also when I drop it off some thing real steep I put it in reverse to help slow it down.