Does anybody know off hand the major differences between a Thiokol 3700 A and 3700B. I am trying to figure out if the hydraulic drive motors , etc. are interchangeable. One carcass I have seems to have a larger front plate that mounts the blade. Also, I notice 15 sprockets on two of these and 17 teeth on a 3700C.
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Thiokol 3700A vs 3700B differences?
- Thread starter Wayne
- Start date
Alaska Snow Cat
Member
This is from an aging memory but,Thiokol made the AC3700, Then came the DMC3700, then The LMC 3700C, LMC3700D and a few other models near the end of production. I owned a AC3700 and looked at a DMC3700 that was for sale and they both had the Allis Chalmers inline 6 turbo diesel which originally put out 200hp and then was increased in the DMC version. The 3700C has the CAT V8 and other changes to the drivetrain. Thiokol made many changes on their snowcats as they built them and I've seen a variety of blades on the 3700 series. You could conceivably but any drive motors you want on them with a little knowledge of volume flows and pressures to best match the pump to the motor imo.
Thank you. I have two running 3700s with symetrical tracks with the AC engine, and one asymetrical track running with the cat 3208. I have two skelton snowcats for parts, so I was trying to figure out which models they might be. I am kind of parting them out to keep what might be needed and getting rid of the extra stuff I may never need.
Alaska Snow Cat
Member
If both of your AC cats are Thiokols then it is likely they have interchangeable parts and any changes to the blade mounts would have been done after they left the factory I would guess. The 3700C versions saw a lot more changes and aside from the drive train components being different I would't be surprised if the mount locations and/or bolt patterns for the engine and drive motors were different. Also the blade mounting improved in the C model with the addition of a angle function but it would be fairly easy to adapt the blade and mounts from one to the other. The AC3700 I had had the factory blade and it was very capable . Wheels will be interchangeable but the got much more robust as they continually thickened the webbing/spokes and hub area. Not sure on the sprockets but if the bolt pattern is the same and the pitch of the tracks are the same then there is no reason they wouldn't swap. I like the symmetrical ones better as the are slightly narrower and don't sag and pull to the outside
Im not real sure about the "A" or"B" models but when I worked on the 3700s at a local ski area back in the 70's the first 3700 we got with the 670I allis Chalmers engine had a separate 12 volt motor to release the Osco brakes , Allis Chalmers injectors in the engine, and a Funk gearbox for the 2 sundstrand drive pumps. Shortly after on the second 3700 that was bought still using the allis Chalmers 670I engine they went to Bosch injectors so they could bring the pressure up on the injectors to 6200, from the 5500 that the AC injectors were capable of. They also removed 4 stacks of springs in the Osco brakes so they could run them off the sundstrand pumps, doing away with the 12 volt pump setup. Also about this time the tillers started appearing so thiokol started using a funk splitter box that three pumps could bolt to so that there was another drive pump available to run the tiller. My belief was when they started with the 3 unit funks for the tiller was when they called it the 3700B. I know when they started putting the cat 3208 , 250 H.P. engine in they were called the 3700C. Just a note even with the best service, oil change at 100 hrs, we seldom got over 3000 hours on the AC machines before engine failure, they were just trying to get to much horsepower out of engines that were designed to produce 140-160 H.P. (JMO) the engines had crankshaft failures, not bearing failures.
Wow, great information. I noticed one of the units has a smaller bracket that bolts to the side of the front for mounting the hydraulic ram to lift the blade (photos attached). One may have been made for a larger heavier blade system. Two have a 6-way blade (up/down, front tilt, side tilt). One without a blade has a blade mounting frame that had an angle function. I may look at the valve boxes and adapt something that will make it an 8-way blade. The 3700C has a 12-way blade. I just found out that a 3700D has a Detroit engine. So I think the A and B had AC engines, the C had a Cat 3208, and the D had an 8 cylinder Detroit engine of some kind. Also, one is orange and one is red and black. Did they change their color scheme?
Attachments
The ones we had at the ski area were red and black mid 70's early 80's machines. we had valley engineering blades made in Maine 6 way and 8 way, never had any with thiokol blades attached. My 2100 has a thiokol 6 way blade on it.Don
I have two, and I don't know where they came from, but they would be 6 way. Up and down, tilt (corners up and down), then one that changes the angle of the blade cut to the ground. However, I have another one that has an angle option for spoiling snow off to the side like a road grader. I may try to figure out how to convert it into an 8 way blade, by adding a pivot and an additional ram. Then just need to figure out which valve will operate it. Could be a fun project. Both of the running cats have hydraulic valve handles behind the main handle control. Actually one has three handles there. I assume they ran something off of the back. I will need to see where the hydraulic hoses go. Right now I am replacing wheels/tires/bearing for a few of the bad tire wheels. Cutting off the old foam filled tires is a pain. So far I am trying a saws-all and a boxcutter to remove them. A place in Reno will mount and fill new tires for me. Just enough of a project to keep me busy for awhile.
At the ski area where I used to work, we had foam filled front tires and when using the blades and after continued use the foam broke up or we would end up with broken front spindles. These machines were used hard ,2 shifts every night, covering hundreds of acres. We ended up just using the aluminum rims with new Goodyear monorail tires. When we mounted the tires tubeless we found that they had pinholes in the sidewalls from the moulding process. We ended up using a product called swepco "southwest petroleum co"that we pumped in the tire and rolled it around ,a slimy liquid that sealed any leaks. We ran tires like that on all the machines and they worked out a lot better then foam filled tires.
I am tightening the axel bearings and replacing a few at the same time. Is there a special grease that is recommended for these? Because of the time spent in the snow, I thought a water resistant grease or marine boat trailer grease might be good. When I took off the grease wheel hubs, I noticed I had three different colors of grease for the 5 axels. Looks like the former owner couldn't make up his mind either.
We just used regular chassis lube, not the super sticky extreme pressure grease like you would use on an excavator pins or loader pins.We installed the seals so the new grease would push the old grease out, I know on the lift sheave wheels we used white lubriplate for extreme cold temp, some times temp and wind chill got to 90-100 below.
Thanks, that makes sense. I was reviewing a lot of comments about the seals being installed with the spring ring facing outward. I think they had the same idea that pressurized grease from the zerk fitting would be forced outward and the lip of the rubber seal would not let water, dust, or whatever enter the bearing chamber. I called Peterson in Utah and they said they have seen them both ways. They said either way, just make sure the chamber inside the wheel is full of grease, so that there is no place for water to collect. It seems that the grease does not need to be anything for extreme anything. Hardly any weight on the bearings (like a boat trailer, probably less than 1,500 lbs per axel.), low speeds (7mph), and not exposed to salt water or any really corrosive environment. I was actually thinking about some white grease my father-in-law gave me 30 years ago. He lived in Tule Lake California and was a potato farmer. He used this white grease up there in a bulldozer idler wheels. He said it was waterproof or something like that. I will find the 5 gal pale and read about it. Probably not made any longer, but I can't even remember the company that made it. I want to get the wheels back on the machine and hook the tracks back up. However, I noticed that it looks like it had the hydraulic ram tightener, but also a tightening bolt with two nuts. One nut is welded to the axel and the other one is loose. I was assuming it was a lock jam nut, but it isn't against anything. Unfortunately, it looks like I will need to crawl under there and see what really is going on. Oh well, just part of the excitement of learning about new things. I appreciate your experience and comments. They are extremely helpful and encouraging.
I can't remember for sure, but I think the hydraulic track adjuster is back between the second and third wheel ,fitting facing to the outside you adjust it out then tighten the holding nut back against the frame, this takes the pressure off the hydraulic cylinder. The white grease is lubriplate made by DA in a black and silver can or tube, that's what I use in my tucker track rollers.
Yes, I need to look at the tightening system, because it looks like the previous owner welded the nut that is supposed to be used to loosen the tension, then when the hydraulics get it to where it is supposed to be, you tighten the nut against the frame and then tighten the jam nut against the first nut. I need to get in there and figure this out, or it will always be tight, which is hard on the tracks when you try to bolt the lacing back together.