Hydrostatic conversion?? Thiokol 602

[gotrocks]

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...

 

[mtncrawler]

I think you'd be way better off buying your diesel/ hydrostatic snowcat and mounting the 601 cab to it than the other way around if that's what you want.

 

[1boringguy]

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]

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]

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]

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

 

[redsqwrl]

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]

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]

outcome could be a easy driving, fairly quick moving snocat, with an epic stance goodlooks

 

[mtncrawler]

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.

 

[MontanaTweak]

Original poster seems to have the acumen to pull it off. I say go for it, if it suits your fancy.

 

[gotrocks]

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]

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]

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]

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.

 

[Wayne]

Any updates on this project?

These kind of projects remind me of the 4x4 custom stuff you used to do. It isn't about the money going in or the money you might get if you sell it. They always cost too much and never sell for what you have got in them. It is about the challenge of reengineering something older into something that would be more convenient to operate. Like old car restoration/upgrades, you will always have the purists that want everything factory and the folks that want to improve drivability, suspension, hp, etc. However, keeping the old parts seems like a good idea in case you decide to sell it to somebody that might want to put it back to its original configuration.

I have a few older 3700 Thiokols now and am playing with them. When I started looking at what I might be able to improve, the first thing I noticed was cracks in many of the previous welds on the frame. If you are increasing hp, torque, axels, rear end, etc., don't forget to look at the welds on the frame. They may need welding or gussets added. The folks on this forum have years of experience doing this stuff, while I am just a beginner too.

I decided on getting the 3700s to get the hydraulic motors for the tracks. I like them much better than the braking steering on the OC-12 rear end. I can counter rotate in a zero-turn situation, which when plowing a narrow road is much easier than braking one side at a time. You could change out the drive system, but now you are into hydraulic pumps/motors, etc. Like others mentioned earlier, it might be easier to just put this body onto a 2100 or 3700 that is already equipped with the heavier drivetrain system. There were at least 4 different 3700s that I am aware of. The 3700A & B had the 200hp Alice Chamlers diesel engine. The 3700C had a Cat 3208 diesel rated at maybe 250hp, and then there was a 3700D with some kind of a Detroit diesel in it. I have also noticed each of these machines had different front idlers and rear sprockets, except the 3700A & B.

Anyways enough rambling on my part. Give us an update when you get a moment. I just love seeing what people that are crazier than me are up to.

 

[gotrocks]

Updates:

My work season was very busy last year so unfortunately the machine sat all summer. Since winter is my offseason, I was finally able to pull the machine into the shop and start doing some needed maintenance on the tracks, clutch and brakes. I had multiple broken grouser bars, broken backing plates, leaking brake slave cylinder, and leaking clutch slave. The interior had 80's shag Mohawk house carpet which just absorbed moisture, and made it musty and moldy. Thankfully the floors had minimal rust started and when it was removed I mitigated the rust spots, primed and touched up the paint.

I decided to try out boat deck foam. I wanted something that worked well in wet environments and was fairly easy to clean. So far I'm quite pleased with the decision. We will see how well it holds up over time.

 

[gotrocks]

Last year when I took it out a few times, I was quite disappointed with the lack of steering control and effort. This was the motivating factor to the thoughts on my original question in this thread post. I decided, I'd try to fine tune the machine some more and see if I could get some more performance out of it in the original form. After my right brake/steering lever started to loose pressure, I knew I had a leak somewhere and did some searching on repairing the stock system. Come to find out I have the OC15 diff and it uses a porta power ram with a through hole piston. That Enerpac RCH-121 ram is extremely expensive ($1200 new) so i searched away on eBay and found a new old stock ram for $500. My thoughts were the current ram was old enough I wasn't going to try and reseal it.

After purchasing it and installing the new one, it sprung a leak and defeated the whole purpose of the new purchase. Not wiling to buy another one, I ordered a seal kit and pulled it apart. The new one just had old seals that I think went dry sitting on the shelf and I can't get too mad on it for failing. Just for curiosity sake, I pulled the old one apart and found that it had pitting on the cylinder walls and was un-usable anyhow, making my purchase for the "new" ram worthwhile.

To remove the brake cylinders, it requires you to pull the diff cover off. I had seen pictures of these and knew from the size it was a big differential, but I didn't expect to truly massive that OC15 is. Another bonus was getting to check on the condition or the brake bands to see if they needed to be relined. Upon removal of the cover, I found a differential, filled with over a gallon to 2 or water along with oil. It drained at minimum 2 gallons of water before the milkshake started to drain out. Seeing this I was able to figure out a good reason my brake effort was so incredibly high.

After flushing out the housing with 10 cans of brake clean, I checked the brake linings to find them in near new condition. They must've been relined at some point in its lifetime. Rust on the components was minimal and the bearings seemed to be in ok usable condition. I'm at a loss how this much water got into the housing.

Since I service most of my heavy equipment, I thankfully had 10 gallons of the proper wet clutch differential oil on my shelf for my D6. I got everything all cleaned up and ensured the diff cover was properly sealed this time.

 

[gotrocks]

Another area I wanted to address was the lighting system. There's no reason to use incandescent lighting on anything these days, and I would always rather have more than not enough lighting on a vehicle, especially offroad and remote. I didn't want however to take away from the nastalgic look of the vintage era of the Thikol, so I kept round lights on all exterior lighting. The original headlight buckets have been updated to clear sealed LED units with functioning high/low beam. The overhead round lights replaced movable searchlight units. I also removed all the old antenna's which were abandoned previously. I will update the coms radio shortly with a new 10w shortwave unit i have.

Another real drawback on this machine is the limited rear visibility with the 80 gallon fuel cell blocking the rear windows. I always add good camera systems to my heavy equipment and found this great 10" unit with a 4 camera capability last year. What I really like it the ability to sync my iPhone to is and use my OnX mapping on the screen. I don't need some car stereo head unit and just want simple camera and mapping capabilities. I only have 1 camera hooked up at this time but might add side cameras as well. If someone wanted to, this can also record the video feeds as well. Not a bad system for around $150 (Ignore the lines in the screen shot of the camera feed its the frame rate of the video feed picking up the shadows of my ceiling fan. Its completely clear to the naked eye)

 

[gotrocks]

Lastly, I wanted to try and tune up the motor some more. I found that the stock Motorcraft single barrel carb was leaking and enough that it likely could've caused a fire being right on top of the exhaust. I did a little digging around and trying to rebuild the carb seemed like just buying a knockoff on Amazon was likely be more efficient use of my time. I got that replaced and plumbed along with an HEI ignition conversion with new plugs and wires.

I haven't noticed really any noticeable power advantage, but maybe after a few more miles, I'll see if theres any noticeable improvement. Another upgrade I'm likely going to do is an electric fan conversion. By doing this I will not only pick up the HP loss made by the fan, but get rid of the plain obnoxious noise it makes. Any RPM over 1000 it gets very loud and adds a lot of cabin noise. The machine always has stayed nice and cool, so hopefully getting the largest electric fan installed will be as efficient as that mechanical fixed fan is.

To help with the noise and engine heat, I covered the engine cover with some reflective foam heat shield. I am very impressed with how much this did help quiet down the engine noise as well as reduce a lot of heat coming off the engine. I haven't used the machine much yet, but the times I've had it up, I care barely keep the doors shut while driving it due to the heat radiating off the engine cover. I'm sure in a super cold environment the heaters would be needed but maybe this will help cool off the cabin until the heaters are needed.

Lastly I did end up pulling off the old Bellevue Warn Winch. I really hoped to get it tuned up some more, but don't have the time to mess with the cable controls now now. I've left all the cab controls intact and can easily swap it back on, but for now, I threw on a HF 12k winch. I have a excursion planned for 2 weeks from now down in OR with friends and just want to get this ready to go so I can test it a couple more times before our long trip.

The last pictures are from my front test trip out. The tracks needed a little bit of adjustment do to slipping but overall good test rip. Brakes worked a lot better. I've learned the faster you go the better the brakes work. It still is no skid steer maneuverability but a little more enjoyable than last year when I took it up.

 

[Wayne]

Nice progress. Getting hot in the cab is an issue with two 3700s I operate. Then condensation on the windshield is another problem when it is cold. I was looking into small heaters with fans that I can direct towards the windshield. Used one last year, but am going to try two this year. I will be tackling the lights this year as well.

 

[redsqwrl]

Welcome back glad you are here. I was hoping you would stay convinced our rear diff was an oc 4. (Giggle giggle) now that you figured out what you have get that v8 jammed in there. Your electric fan idea will burn up the 240 pretty quickly so just get to the v8!.

If you do go electric, bring your mechanical, fan and bolts and 2 gallons of liquid with you. Electric Fans just move the load to the alternator and do a poor job unless properly shrouded. (You know this) most folks dont realize that when the fan motors get warm electrically their resustance goes waY up. Fan hp goes down 4x and air moved is not at the advertised rate.

Glad your having fun. Those warn winches are the best.