Two speed modification for PT 422/425

KentT · Apr 12, 2007

Just wanted to "close the loop" on this topic. In researching this whole need for more torque to climb the Tennessee hillsides, I found out that I have White RS model, 12.5ci wheel motors on my PT-425 purchased in Dec 2000. They are rated at 1500 PSI continuous and 1750 PSI maximum. I had earlier, mistakenly thought that they were White CE model motors rated at 3000 PSI.

Consequently, they will not handle the pressure that would result from this mod. They would need to be capable of handling up to 3000 PSI, which they are not.

I'm now looking at replacing the wheel motors to address this need....

stray · Nov 2, 2010

I finally had the opportunity and reason to try out this wheel motor configuration. I am sad to say that although it slowed the PT down by half it did not double its climbing and push power. I believe because of bypass seepage in the wheel motors the supply of oil to the motors was not enough to overcome the seepage enough to take advantage of this configuration. All said and done in this configuration and my motors (over 1000 hrs) my PT 422 did not climb any better that the original configuration.
I would be interested in hearing how the PTs that some have changed to a larger wheel motor but still the same tram pump are doing in the pushing pulling and climbing with a load area. With a full Light material bucket (48 inch 10 cu ft bucket) say with dirt on the heavy side (you know where the PT puckers some when you turn) and the PT good and worm and running for 30 minutes or more. How steep of a hill will it climb.
This Question also applies to any of you all with a 422 or 425.
It would be also good to know how the larger PTs do at this.
So the Question is how steep and how heavy a load will your PT do?

KentT · Nov 3, 2010

Stray,

With my larger CharLynn S-series 21.2 ci (I think -- not sure -- danged CRS!) wheel motors I operatate on 20-25 degree slopes at will, full LM bucket, mowing or whatever. It will often start spinning if I don't lift the 48" brushcutter a little to put more weight on the tires, though. I've hauled incredible amounts of mulch (tub grinder tree and stump remains) in my LM all over my lot.

I'm approaching 700 hours on my tram pump, but I've been running 20W50 Amsoil since about 200 hours (or a little more). Otherwise the whole running gear is stock Kohler-powered PT425. It'll spin all four wheels (WW-loaded bar tires, reversed wheels) pushing into a pile of dirt but I do NOT like doing that, so I immediately correct it.

I'd suggest that somewhere in the 17" - 18" ci range for most all-around users. Mine only goes about 5 MPH, full-treadle, full-throttle but that works well for me, where I'm using it. Would be too slow for significant lawn mowing on flat land, for example.

stray · Nov 3, 2010

Thanks Kent, This is very good info for me as it seems my Pts only short coming is its climbing and push power. As it stands now I can push my peddle all the way down and it will not kill the engine. The PT ether goes or it just sets there and tries, bypassing the hyd fluid I assume through the wheel motors and tram pump. I am thinking that I could try the higher viscosity oil as a first stage fix and see what kind of satisfaction that gives. Then later maybe going to the larger wheel motors. Question? If you could just say take your 21.5s off and put me some 18s on with the same hrs of use. And it not cost anything. Would YOU elect to do so? Just a test to see if you would really prefer the smaller motors.
Another Question? What kind of additive is out there for Hyd oil that will raise its viscosity? Will something like LUCUS work for this?

Again Thanks very much for the info.

KentT · Nov 4, 2010

Stray,

For my own specific uses, I wouldn't trade my larger CharLynn S-series motors, because of the slopes I'm working on. For example, I mow with the 48" brush-cutter down steep slopes like this, lift the brush-cutter, and back back up the hill. I'd rather have too-much displacement/torque on the wheelmotors than not enough, in these circumstances, trading climbing power for speed. In these situations, traction is now my only concern, not the power to back up the hill:

http://farm4.static.flickr.com/3347/3498627033_7effce4930.jpg

http://farm4.static.flickr.com/3563/3499444500_ebdc569d20.jpg

That being said, I'd feel much more comfortable about the durability (especially with the reversed wheels), if I'd used motors specifically designed as wheelmotors, to handle the side-load and stress. For example, this is one heck of a good price (about 1/2 of what I paid) for White CE motors (like used on the new 425s, though larger displacement than the 14.3ci from Tazewell).

https://www.surpluscenter.com/item.asp?item=9-7741&catname=hydraulic

If I were doing it again, today, I'll likely get those at this great price, buy the bolt-on wheelmotor boxes and larger 1.5" front wheel hubs from Tazewell (you can get rears elsewhere), and simply cut my old wheelmotor boxes off and bolt the new setup on. It'd be as cheap if not cheaper, and I'd have a more-powerful version of what Tazewell is using on the new ones...

That would give you about 50% more torque than the 12.5 ci White RS-series motors you have now (a noticeable difference, I promise you), stronger wheelmotors, and probably still go about 6.5 - 7 MPH, full-throttle, full-treadle...

stray · Nov 4, 2010

Yes that is a great price. That would be the way to go. I need to contact Power-Trac and see if it will be better to buy there wheel boxes or fabricate my own or maybe something else. I can decide that after receiving the motors. Also it looks like machining the existing hubs to the 1.5 taper may be the best option there. I hope it don稚 take me as long to do this as it did to try out the optional wheel motor configuration. Thanks for your help Kent.

P.S. My gosh be careful on those hills!!!!!