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Thiokol differentials

Hi Guys,
Just a quick note in reference to rear diff fluid. SNOWCAT PAT suggest in a phone call to him that I try Caterpillar TO-4 30 weight. Man am I impressed! changed the fluid once before to something that was used for trans and wet brake bands but the stuff was really thick and heated up quick. The new TO-4 steers a 100 times better and so far seems to run ALOT cooler! I cant believe how much easier it is to now steer. I use probably Half the pull force to turn. I cant find the container I used for the first diff change and I dont remember what it was but this TO-4 is GREAT stuff! Thanks SNOWCAT PAT!


CATERPILLAR "TO-4": $67.95 5-Gallon bucket
 
Hey Sno-Ops, Glad it worked for you. I like action of the TO-4 much better than Tractor Hydraulic Fluid. I've read (for what its worth) that its also better for the gears as a straight weight and has a friction modifier developed by Caterpillar for wet brakes. I happen to use Shell Donax TC-30, it has the TO-4 rating. I wonder though if the Cat product is better. The Shell product is cheaper.

I should mention that Thiokol/ LMC snowcats equipped with the differential as the hydraulic reservoir should use the lighter THF. I'm not sure if the hydraulic pump in those systems would be happy with the TO-4/30W. The TO-4/10W might be OK with the pump but then might be too light for the gears.

-Pat
...trying to live up to the name Spryte Imp-rovement!
 
Snowcat Operations said:
Now here is another dumb question. How often do you change the fluid? Once a season is over? I figure on 600 hrs per season.
Click to expand...

The book I have says to change every 150 hours of operation and at the beginning of each operating season. I think I downloaded it from this site but I can't find it now.
 
I would think since the cost is cheap enough that a change at the begining of the year. Half way through and at the completion of the year would really keep the fluid nice and new in the rear diff all year.


Snowcat Pat. My next Cat will have an OC-12 with a blade. DMC1200. What do you suggest for that other than a 10 weight. Temps I run at are between -20 and 32 degrees. I will sometimes drop below those temps but not often.

ALSO does anyone know how many gallons an OC-4 takes?
 
I have a 2100 with an OC-12. My manual says to run gear oil in the main case and 30 weight in the drop boxes. So far, I've seen no mention of anything similar to this...just want to make sure I'm doing the right thing. Mine runs cold and steers great...
 
HELLO SNOWCAT...I have a Thiokol Spryte...1977....model.1201047-104..The differential has broken up would you know which model differential differential I need[ ?. and where I might be able to find a rebuilt unit or parts....Regards Tom....quote=Snowcat Pat;76181]The drop boxes for the OC-4 are chain reductions. The drop boxes for the OC-12 are gear reductions available in both 2.44 or 1.83 ratio.
I just finished rebuilding my 14th OC-12 and I think I'm starting to understand it.
I've tried several different oils in the last 18 years and I now use only Tractor Hydraulic Fluid brand Shell Donax TD, or sometimes Donax TC-30. Lots of these cats have a hydraulic system that combines the rear end oil with the hydraulic oil so it has to work for both. Change the oil often, when warm, and in the spring before storage.
Steering? Don't drag the brakes!

Snowcat Pat
Wallace Idaho[/quote]
 
I have a Thoikol Spryte 1977...Model 1201047-104 The differential has broken up..Any idea what type of differential this would be ? and where I might be able to find parts...I need to get this thing running...Thomas
 
mtntopper said:
With the OC4 rear end in the Imp, I have used and highly recommend the Shell Aero mineral oil that is used in airplanes. I used Shell Aero 50 and it works great in the Imp. You will have excellent braking/turning ability with very little wear on the brake bands. It came highly recommended to me from several people with a lot of brake steer snow cat experience. :thumb:
Click to expand...


Same oil that we have been using in our Imps here (C-4 transmissions) in the winter and seems to do a good job and steering is pretty good as well.

My Imp sets pretty much all summer unless I want to take it for a spin around the yard and then my wife gets really P.O.'d about the new grass "Turf lines" all over the place from turning.

I will change the oil in the fall and then every 100 hours or so of running (much cheaper than rebuilds). The Shell Aero 50 can be bought at any airport that sell aviation gas. In Fairbanks, they sell it at the Sam's Club. I would assume that is because we have so many Imp owners here... oh, and a few airplanes too...
 
thomas said:
I have a Thoikol Spryte 1977...Model 1201047-104 The differential has broken up..Any idea what type of differential this would be ? and where I might be able to find parts...I need to get this thing running...Thomas
Click to expand...

Show a picture of the diff and I'm sure someone can ID it. Comparing with the pictures at the beginning of this thread should tell you which diff you have. With the model/serial number info, I think Peterson Equipment in UT can give you all the nitty-gritty details on your cat. There are a few members here who may have the parts you need.
 
Great thread,

I have the dreaded C-4 rear in my Ractrac Sprite (=Thiokol Spryte). The previous owner told he replaced the gearbox some time ago. Its fully working, and so far no probs - although I'm trusting his words because I've yet to drive it myself...

Could someone tell me what are the weak points of these C-4 rears? Maybe I could fix the probs before they occur, I have full CNC-machining facilities so I'm not afraid of some work. Still, I would really like an C-12 which I haven't been able to find from here... :sad:

I'd really like to fit hydraulics and snow plow but with C-4 it seems stupid thing to do :hammer:
 
Yes. A snow plow is a bad idea with a c-4 equipped Spryte. Unfortunately theres nothing much you can really do to improve it. There are several OC12s floating around. They run from about $2,000 for a very good used one to $6,000 for a new one that has never been used. I can get both.
 
The biggest problem is getting the thing here, it might even double the price (first land transport inside US, the shipping in a container to Europe, land transport in Europe, then EC Tax 10% and on top of everything Value Added Tax 19%...). I'm not sure if the maker of my "Thiokol copy" ever used OC12 rear, if they did - then I have a chance of finding one from here - but to be honest, these parts don't grow in trees here.
 
Mainer said:
Here's the back-end of my 61 Trackmaster. Just bought it and have it in storage...haven't had a chance to touch it or dig into it at all. Runs well as-is but I'd still like to do a chassis-off restoration. The previous owners went through a few 1/2 ton Ford pick-up back-ends and then went up to 1 ton and it's been fine. They pulled a 2,800 lb drag with it.
Click to expand...
how did they hook up the rear ends are there two drive shafts
 
Hi. I'm totally new to the super cool world of Snow Cats, but I have a differential question. From looking at pictures of the OC-12 (and making the assumption that most are of similar operating principle), they look like regular open differentials with band brakes on the output flanges, and then reduction boxes going out to the drive sprockets. Is that basically whats going on? I've read that for fast track layers this is a pretty inefficient approach, and that most military fast track layers use a sexy triple differential system. Can anyone speak to this? Thanks!
 
vwdevotee said:
Hi. I'm totally new to the super cool world of Snow Cats, but I have a differential question. From looking at pictures of the OC-12 (and making the assumption that most are of similar operating principle), they look like regular open differentials with band brakes on the output flanges, and then reduction boxes going out to the drive sprockets. Is that basically whats going on? I've read that for fast track layers this is a pretty inefficient approach, and that most military fast track layers use a sexy triple differential system. Can anyone speak to this? Thanks!
Click to expand...
the older armor like the m113 family simply used some thing like a bombadiar weit a toeque biasing diff and band brakes to steer and a set of disc brakes on the output shafts for piviot steer the mo modern tanks are now using a varrator system like the snow trac but instead if a belt they use essentialy 2 automatic transmissions on either side of an open diff i describe it this way be cause with out the power flow diagrams its the best way to describe it. they use plannitary gears and clutchesto varry speed between outputs through the differential this is done for both steering effeciency but also traction and high speed control imagin running at 50 mph and de clutching a track and braking one side to steer even if only for a second.
 
Boggie,

Would you have any info relating to the routing, and hook-up of the cooled OC-12, hydraulic lines? My Differential is filling completely full to the top case cover, and I think it may be hooked up wrong.

Snowcat Pat has completely rebuilt my unit, and it has "0" hours. My choice of lube is Chevron Synthetic All Weather THF.

The Cat is a 1976Thiokol 2100C

Thanks for any tips,

fischerrc4
WA State

fischerrc4@yahoo.com
 
I don't want to hijack this thread, but is there an exploded view or disassembly photos of one of these differentials somewhere?

I'm inexplicably drawn to understanding mechanically, how they work...
 
Av8r3400 said:
I don't want to hijack this thread, but is there an exploded view or disassembly photos of one of these differentials somewhere?

I'm inexplicably drawn to understanding mechanically, how they work...
Click to expand...

go back to the snowcat main page here on the forums there is one there that I sent in pdf format several years ago part A and part B
 
Snowcat Operations said:
Hi Guys,
Just a quick note in reference to rear diff fluid. SNOWCAT PAT suggest in a phone call to him that I try Caterpillar TO-4 30 weight. Man am I impressed! changed the fluid once before to something that was used for trans and wet brake bands but the stuff was really thick and heated up quick. The new TO-4 steers a 100 times better and so far seems to run ALOT cooler! I cant believe how much easier it is to now steer. I use probably Half the pull force to turn. I cant find the container I used for the first diff change and I dont remember what it was but this TO-4 is GREAT stuff! Thanks SNOWCAT PAT!


CATERPILLAR "TO-4": $67.95 5-Gallon bucket
Click to expand...

Is this oil still working out for you in your C-4 diff? Why 30 weight vs. the recommended 50 weight?
Thanks-
 
Because Sno-ops machine has the OC-12 (1450 Super Imp) where yours is the OC-4 (yes let me repeat that "OC-4") in a 1404 Imp.

While I'm being insistent I'll add that I don't think shell Aeroshell aircraft engine oil is nearly as good as TDTO transmission oils. From what I've seen looking inside and rebuilding these diffs.

-Pat
 
I ended up going with the Caterpillar TDTO 50 weight in my 1404. I did notice an improvement in steering, but not to the extent that Snow Ops did.
 
Our 1988 LMC1200 has the OC12 with drop down boxes, hydraulic pump and cooler. No other hydraulics on it. What would be the best oil for it and how much will that setup take? I've poked around here and it seems that Shell Donax TD would be a good choice. Except now Shell calls it Spirax. Thanks.
 
any of the tractor oils or wet disc clutches I run amzoil power shift in mine I'm not sold on one oil being better than the others because its some one like shell that makes the oils sold by the tractor company's like cat or john deere. those oils by the way have a good following here I wanted synthetic oil my reasoning for amzoil
 
Thanks for the info Snowtrac. Any idea how much I need? I have heard from 6-8 gallons.
 
if you have drop boxes and no pump its about 5.5 gallon too fill to the plug if you have no plut add another gallon over the plug for additional cooling as per snowcat pat
 
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