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Hydrostatic conversion?? Thiokol 602

gotrocks

New member
So I recently purchased a good condition Thiokol 602 locally and have checked off a bucket list item of owning a snowcat. I've always lived in the PNW and ridden snowmobiles for year and winter is my favorite time of the year. We have some acreage in the mountains locally and have a number of miles we can go enjoy the machine to justify the purchase.

So after my first couple trips out with the machine I have been left wanting more. I fully understand the uniqueness of the OC-4 transmission and steering system. Its not like my old 70's D6C Cat to operate and steer, however I just feel theres a lot of better ways to modify the machine to be easier to operate and more enjoyable. I'm sure I'll anger some purist, but I'd love to replace the drivetrain with a modern LS powertrain and do a hydrostatic hub drive conversion with joystick controls.

I owned and operated a custom 4x4 fabshop and have built many custom vehicles from scratch and have the full shop to fabricate most anything, I currently own and operate a heavy equipment business and maintain my own machines so the hydraulics don't worry me. What I'd like to know is what resources are available to source parts outside of companies like PistonBully or Bombardier. I'd love to do a retro style build to make it very similar to the Piston Bully Scout but keep the very cool nostalgic look of the 602. Again this isn't my first rodeo tackling something unique, just trying to put some feelers out there since this world of snowcats is new for me.

Here are some pictures of the machine I just bought...
 

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1boringguy

Well-known member
GOLD Site Supporter
Might also look into where they sourced parts/drive system, for the new snowtracs. I'm guessing the construction industry (bobcat?) Rather than the commercial snowcat industry.
 

redsqwrl

Bronze Member
GOLD Site Supporter
I considered a ground up build. Custom cab. Bombardier style idlers. Pb tracks. I was a bit disheartened to learn hydro drives yield 50% hp output to hp input. That and my budget doesnt support the capital to rebuild the drives in a timely fashion. I even went as far as procuring a 2spd bobcat to r and d. I flamed out on the idea. I am a controlled diff guy.

Power to both tracks.
Simple like me.
Reliable
Predictable
Light
Higher hp to weight ratio
 

gotrocks

New member
Well I appreciate the input so far. I understand there are easier ways possibly to do this, but I'm just trying to think outside the box a little. HP wise I'm thinking 300HP at minimum so, hp loss isn't as much as a concern. I know that power and drivability will greatly increase with the super simple LS V8/auto swap, so I'll likely for now just get it swapped in before next season. I'll also do some maintenance on the brake system and run it to see if that gets me closer to what I'm shooting for.

After some digging it appears that I can get some better drivability from my braking system and hopefully reduce some of the input effort its requiring. Right now my wife and kids wouldn't last long driving it. Heck my arms where feeling pretty gassed after about 3 miles.
 

tommu56

Bronze Member
GOLD Site Supporter
I know its over kill but what about a system from a JD hydrostatic dozer proven (probably not cheap)?
 

redsqwrl

Bronze Member
GOLD Site Supporter
Well I appreciate the input so far. I understand there are easier ways possibly to do this, but I'm just trying to think outside the box a little. HP wise I'm thinking 300HP at minimum so, hp loss isn't as much as a concern. I know that power and drivability will greatly increase with the super simple LS V8/auto swap, so I'll likely for now just get it swapped in before next season. I'll also do some maintenance on the brake system and run it to see if that gets me closer to what I'm shooting for.

After some digging it appears that I can get some better drivability from my braking system and hopefully reduce some of the input effort its requiring. Right now my wife and kids wouldn't last long driving it. Heck my arms where feeling pretty gassed after about 3 miles.
I hear this stick effort comment a lot. (Weatherby stated his stick pull effort was high, and everything was perfect on that cat) I have cats that steer easily with finger input. And others that people have upfitted with vacuum brake boosters. I operate my cats with throttle and stick input together.
 

mtncrawler

Bronze Member
GOLD Site Supporter
OK. I'll be the purist here for the moment. While you're busy fabricating this 300HP+ LS modification into a machine designed for about 115 ponies what do you think the outcome is going to be? Final drive wise I mean. Or sprockets. Or front axle. Or rear axles. Is this build some kind of social media thing? Not trying to be unsupportive, I just don't understand why. You have a very fine looking somewhat rare 602. Absent the passenger side roof hatch makes it one of the few non-military machines built.
 

redsqwrl

Bronze Member
GOLD Site Supporter
outcome could be a easy driving, fairly quick moving snocat, with an epic stance goodlooks
 

mtncrawler

Bronze Member
GOLD Site Supporter
Sure. And after all the time and money spent on this conversion, the final result is a machine that's constantly breaking really hard to find parts and when the time comes that repairing it becomes a burden it can sit broken down out in the yard for years! Better to think Weatherby with this one and get another one that fits your needs. After all, owning one snowcat is never enough.
 

gotrocks

New member
OK. I'll be the purist here for the moment. While you're busy fabricating this 300HP+ LS modification into a machine designed for about 115 ponies what do you think the outcome is going to be? Final drive wise I mean. Or sprockets. Or front axle. Or rear axles. Is this build some kind of social media thing? Not trying to be unsupportive, I just don't understand why. You have a very fine looking somewhat rare 602. Absent the passenger side roof hatch makes it one of the few non-military machines built.
Swapping in an LS is very straight forward and simple for me to do. I've done countless projects personally and for customers back when I ran my custom vehicle fabrication company. So cost/effort for just a drivetrain swap is the easiest first effort I see doing.

Regarding the sprockets, axle shaft strength questions, my limited knowledge specifically would be why would this be a limitation? With an automatic, theres a lot of cushion for those components with swapping over to an automatic since the torque converter in the transmission would buffer the power input. Its not like in a rock crawling situation where your dropping a tire into a hole and trying to throttle out with lockers on. I'd imagine the track system has additional absorption of the power transfer and shouldn't shock load the axles. My sprockets were redone by peterson before I bought it and seem to be in great shape.

I'm not going to pretend I know it all with these machines, I'm here trying to get some feedback and learn an whole new world I'm not directly familiar with.

BTW I'm not a fan of social media, I deleted my business accounts years ago and much prefer forums honestly. I very much enjoy the dialog between people on a forum and enjoy seeing and sharing the process of builds through this type of setting. I feel that its far more real and honest. Getting to see guys try, fail, try again on different out of the box ideas in this type of setting and throw ideas back and forth while building a project is where its at. If I proceed in building this 602, I will be mindful to keep all the original drivetrain parts, so it could be returned to stock form if I decided to sell it and someone wanted the original boat anchor engine/transmission. Sorry if it offends anyone, but anything with a carb is on par with a boat anchor to me.
 

redsqwrl

Bronze Member
GOLD Site Supporter
You are hitting the mark on the head.

Snowcats are all about compounding torque. I love rigs that run. Fi is a great way to eliminate evaporating alchohol in essence better runability and ability to sit.

Im getting comfortable running my mouth about snowcat drivetrains. Some people put 100% of their effort and ability into one project and that makes them happy. Some pay other people for the same result.
If i get bored with something it sits. If the machine cant do what i want or need it to do. It sits. I find my thrill getting this old crap to do anything. (Example)
Power was out multiple days. Shit snow rain mix storm. After 12 hrs i needed to step away from the coffee cup and wood stove to refreeze freezers and pump out drain tile system around perimeter of house. I fired up a 1930 blackstone. Why not use the automatic transfer and natural gas fueled generator..?.. well cause i was home snowed in and nothing better to do than see if it would start.

Social media is all about glamour shots. You seem like a person who will post an overheated engine while learning wether or not hydro works with the girlfriend is running it.
 

mtncrawler

Bronze Member
GOLD Site Supporter
OK, more feedback. I don't know whether the OC-15 will put up with triple the power or not. The predecessor machine, the Trackmaster final drive was two Dana 60's, one for each track. And that was the condemning failure point that lead to the OC-15. So is a rock crawler comparison valid? The OC-15 does not have gear reductions except in it's bulldozer form. So maybe. What about the grousers? 601 grousers are not heat treated like the J-styles on C-Models and 2100's and other work ready machines. And they trap water in the tubing. The front axles in these machines can be a weak point too. Power = speed =?. I did look at the 6.0 LS in my pickup and wondered how that would fit into the 24" tunnel width of my 601. And cooling it will be a challenge. Something to consider. With a civilian machine you might have the 240 instead of the 223. An injected 300 / C-6 auto would fit nicely. Good luck.
 

redsqwrl

Bronze Member
GOLD Site Supporter
I can vouch for the oc 15. There is not a motor made that will harm that ring and pinion. Its massive. The bearings are even bigger.
 
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