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Transmission + Hydro?


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#1 Cvans OFFLINE  

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Posted October 23, 2011 - 07:03 PM

I'm starting to think about another project :say_what: and would like to pick you minds about something. I'm thinking about placing a hydro rear end behind a three speed transmission to increase the versatility of the vehicle.

Would first gear turn the hydro fast enough to function?
Would I have to speed the up the input to the transmission to make this combination effective?

Before going through all the work I'm wondering what your thoughts would be on this matter.
Thanks for your input!

#2 MH81 ONLINE  

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Posted October 23, 2011 - 08:07 PM

How about the other way? If you feed the hydro first, the output from the hydro would feed the more forgiving gear tranny.
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#3 Cvans OFFLINE  

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Posted October 23, 2011 - 08:43 PM

I couldn't agree with you more. The problem with that is the project would become much more complicated in that configuration. If I leave the engine,transmission configuration as is and just replace the standard differential with a hydro rear end the project would be fairly simple. Boy do I like simple:smile1:

I think I better check rotation also!

#4 JDBrian OFFLINE  

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Posted October 28, 2011 - 09:44 AM

Chris, the hydro has to be turning pretty fast to get enough flow to work properly. Gearing down the engine with a transmission wouldn't work very well unless the ratio was close to 1:1. You would not get any more torque out of it because you will still be limited by the hydro. Putting the tranny after the hydro would be like having a 3 range hydro. Done right this would give you a bull low range, mid range for average work and a high for transport. That would be an interesting project.
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#5 olcowhand OFFLINE  

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Posted October 28, 2011 - 09:53 AM

I've taken a bit of time to think on this one, and I have to agree that the tranny ahead of the hydro wouldn't likely have a pleasing result. Hydro's are more efficient at higher rpm's. Lower rpm's would lower pressures, and likely reduce torque too much. Now the hydro ahead of the tranny would be quite different all together! That would be like my Al;lis 720, as it has a 3 speed differential. But, most hydro's dump oil out the output area, so it would be a challenge to figure out the engineering required. I know some of the Eaton hydro's were self contained, so might be an easy to do with one of those. I can't remember the Eaton model, but such a self contained Eaton was in a later Wheel Horse tractor I had.
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#6 olcowhand OFFLINE  

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Posted October 28, 2011 - 09:59 AM

Just to note, if the standard transmission is just a 1:1 in 3rd, there would be no increased speed in high gear, just 2 lower speeds.

#7 skyrydr2 ONLINE  

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Posted October 28, 2011 - 11:20 AM

Won't work for more speed, only slower, as ALL HYDROS ( garden type units) are at least 2:1 meaning pump volume to motor volume is half. Just to say, pump v is 17 gpm at 3600 the motors max volume would be 34. So your left with half your imputed rpm .
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#8 Cvans OFFLINE  

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Posted October 29, 2011 - 09:24 AM

Thank you guys for putting all the thought into the question. I've decided to abandon the idea. As was stated, every hydro tractor I've seen has had gear ranges in the differential. Sometimes thinking outside the box isn't fruitful.
Thanks again.

#9 JDBrian OFFLINE  

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Posted October 29, 2011 - 11:07 AM

Sometimes thinking outside the box isn't fruitful.
Thanks again.


Sometimes... but never stop! The original hydrostatic transmission was probably considered outside the box as well!

#10 olcowhand OFFLINE  

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Posted October 29, 2011 - 11:31 AM

Now if you had the hydro in front, turned a truck/car transmission backwards to step up the speed, then hooked to a car style rear end.....then you'd be cooking! High gear would become low, low would become high, with the hydro controlling the variable. Climb back outta that box Chris! :D

#11 Cvans OFFLINE  

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Posted October 29, 2011 - 02:20 PM

Climb back outta that box Chris!


Being couped up in a box is so boring! :smile1:

#12 Toolpartzman OFFLINE  

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Posted October 31, 2011 - 06:51 AM

Jumped in here looking for hydro help myself and maybe I can help. Not clear on old hydros but the specs on a G730 Hydro Gear calls for min/max input speeds
of 1800/3600 RPM respectively with an overall transaxle reduction of 27:1. I'm not clear on what you hope to achieve exactly, but if the hydro you have in mind
is capable of swapping out relief valve springs to change dump pressure, you can tune it to do most anything you want within those parameters.-Hope this helps some.

Thinking outside the box gives you a better view of the box.

#13 Toolpartzman OFFLINE  

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Posted October 31, 2011 - 07:02 AM

Forgot to mention that this is a typical variable speed piston pump w/charge pump. Just happen to be trying to solve a problem with it. Out of a CC GX1054 mower that CC says max load is 902 lbs (my calculations) and its currently pulling 3800lbs. It doesn't like it and its growling but it brings HP in just as smooth as you could ask.

#14 Cvans OFFLINE  

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Posted November 01, 2011 - 07:37 PM

Thanks for the information. I've decided to drop the project as unfeasible. I did just bring home a Ford 165 hydro with a 2 spd. differential and limited slip. This should work fine once I determine that it is mechanically healthy.

#15 hammerdwn20 OFFLINE  

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Posted December 03, 2011 - 08:52 PM

DetroitDieselguy671's Channel - YouTube

This guy has the hydro trans driving a cub lo-boy trans and rear. give it great pushing power and a fast transport speed.
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