Thiokol 2100c

New to me Thiokol 2100 c. Has a 390 ci Ford from a 66/67 Mercury car mated to a C6 trans and an OC-12 rear diff. Been sitting for at lease 5 years at the previous owners, not sure before that. Plans are to make it run(needs carb over haul) and drive(drop box has hole in it). Simplify the hydraulics as much as I can, it doesn’t have anything for a blade or groomer just the hoses that leak. Rebuild the tracks and try and narrow them up a bit. Junk the single cab for something with a co-pilot seat…like a 40’s truck cab and front end. And of course a passenger box on the back.…..Dang, now that I’ve written it down it seems like a lot of work….better get busy.
 

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Snowy Rivers

Well-known member
Welcome to the FORUM

The Few, the proud, the 2100 owners. :thumbup:

These are a beast of a machine.....I own a 2100B and have been doing a restomod...
I am swapping an S10 Blazer body on mine.
Currently I have an S10 pickup cab on the chassis....But decided last fall to go with the Blazer to get 4 doors and more room.

Sky is the limit and your imagination can take you to wherever you want to go
The 57" wide tracks can be narrowed up a couple different ways.
Cutting off the outer and inner belts and the same on the grousers....Or go with two 12" belts and use the 43" grousers (Must do some redrilling of the bolt holes...

You mentioned a hole in one of the drop boxes.

Getting the Diffy out, apart and checked out is a must do.

The hydraulic system is not that complicated......Just be sure to maintain the Priority flow divider and the 50/50 flow divider that feeds the steering system.
You can get rid of most of the extra hoses and stuff.

Just maintain a free flow on the one side of the priority flow divider so the pump does not stall when you pull both steering levers to stop the machine.

There are a few different ways these machines were plumbed up.....But 40-50 years on.....anybodies guess as to whats been done.

I have made many change orders on things as my project has progressed......The 2100 has some real possibilities.

This forum is populated by many great folks that will offer advice and help....
There are only a few 2100 owners here.....Mainly because of the size of the machine.....

Lots of potential.....
The OC12 is pretty simple to rebuild....Just a heavy beast is all.....
I have many pictures on my Thread of the diffy rebuild....

Keep us in the loop.
 
Had mini-me helping out disassembling stuff…got the diff out, one drop box is in sad condition
 

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Snowy Rivers

Well-known member
Yup.
That box is a mess.
Looks like the lower gear is pretty well Fubar'd too.
If you go through my project posts There are lots of pictures of the Rebuild on my diffy
Contact SNOWCAT PAT in Idaho (Spryte improvement) on the web.

Nancy answers the phone and is great to deal with......
Once you get your diffy apart you can figure out what you need.
These folks can supply the gaskets.
All seals are standard stuff (Ebay)

The OC12 HAS 14 BEARINGS
This can get really spendy....

I scared up all my bearings off ebay (NEW OLD STOCK STUFF)
Well worth the hunt to save a huge amount of $$$$$
Getting the diffy apart takes patience and care. LOOK OVER MY POSTS...

The drop box gears come in two (2) ratios You will need to count the teeth so you can get a good set
1.83:1 > (33 tooth lower and 18 tooth upper) 2.44:1 > (36 tooth lower and 15 tooth upper) 1.83 and 2.44 ratios

The ring and pinion are either 6.14:1 or a 5.44:1 ratio
Any of the R&P ARE TOUGH TO FIND

Keep all shims together and mark them as to where they came from (Tag and bag)
With this you can replace all the bearings and things will all go back together with no issue.

The OC12 drop boxes should have steel guards that bolt to the chassis to keep them from damage

When you dig into the diffy......Bands may need to be relined.
Witness mark the different parts of the carrier/equalizer and all the small pinions so everything goes back where it came from
Getting the drums back on...THE PINIONS MUST BE TIMED.....We can discuss that down the road when you get there


KEEP US IN THE LOOP
 
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Snowy Rivers

Well-known member
Just an FYI
ALL OF THE TRACK WHEELS WILL NEED TO BE APART and checked.

The bearings in these get water in them due to the seal design AND WHERE THEY RUN....They need end of season maintenance every year.... LIKE A BOAT TRAILER....
When the bearings fail they mess up those lovely aluminum wheels......

I have a few here now that the inner bearing went away and messed up the wheel.
Going to bore out the damaged bores and sleeve them
 
Well shit…this project just came to a screeching halt…till I figure out what I’m gonna do….find a complete good diff or part it out or sell it as a project…..damnit
 

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Snowy Rivers

Well-known member
Would appear that possibly the bearing on the top gear grenaded and the carnage took out the case from the inside out....
This bad boy made some real bad noises....

What does the inner case look like...Ring and pinion ???? and the equalizer....bands ????

The gears and the drop box can be replaced.

After being into these boxes (Tractors too) The thrust washers used in the compensator are responsible for chewing up a lot of metal TRASH.....This junk destroys bearings and then a major failure happens/

I did extensive mods to my diffy...Added better thrust washers and debured the equalizer pinions.

If your center case section and gears are good....this mess can be cleaned up and fixed easily....

The crescent shaped plate with the nuts welded to it in the inner case where the drop boxes bolt on are not factory.....I have been into a few of these cat OC12 and there are heavy flat washers and the lock nuts all the way around.

The modification is neat and clean.....but not stock.

The boss where the carrier bearing slides into (Piece missing) Was the chunk of aluminum all chewed up...or ?????

I am very curious what the rest looks like...


Some pics of the thrust washers I retro fitted to my case.

The parts used at the factory are nothing but shim type material (Like pinion shims) and are soft and wear out, break up and go through the gears and bearings..The bearings can and do explode when this junk goes through them....and you see the results....
Your top row...center picture.......inner bearing likely jammed from some crap from a thrust washer....bearing went away....balls fell into the case...went through the drop gears....Stress was far beyond anything the aluminum could stand and the parts all failed.......



This is not uncommon in these boxes.....I looked at two this winter that were for sale.....both had similar failures. Guy wanted waaaaaay too much $$$$$ for the junk....And without seeing the insides...NOOOOOOOOOOOOOO WAY

If your center box is not broken....should be reparable ....
 

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As you can see the bearing capsule is busted out, other than that case is ok. Drop box is garbage. My best guess is the outer bearing on the top gear grenaded first cause there is nothing left of it, causing the inner bearing to fail it actually split the races down the centre where the balls ride and in the same Kaboom busted out the better part of the diff carrier bearing capsule. Be good for spare parts, gonna try and source a narrow axle instead of trying to piece this back together
 

Snowy Rivers

Well-known member
Sounds like a plan.

The OC12 from a spryte will be narrower.....
You might want to call Spryte improvement up in Idaho and see if Pat has any goodies.

As I mentioned...If the Center box, R&P is good and the other side is OK
Fixing your box is no big deal.

Finding a complete box at an affordable price is gonna be $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
I know a fella locally that may be able to help.

He runs several 2100 and a 3700
I will scare up his number and PM it to you...

WE have traded parts back and forth over the past couple years.
I traded my single cab for a pair of tracks and a couple aluminum road wheels.

He is up near Mt Hood

Let ya know
 
Cabs all gutted and ready for removal
 

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Snowy Rivers

Well-known member
Oh yeah buddy......This looks all too familiar ....

Some pics taken during the tear down
Piccy of the LH independant front axle suspension (Original axle was bent...torsion ends shot....junk)

S10 CAB GOING ON.....Being replaced by an S10 Blazer 4 door....

So much fun
 

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Got the cab off and pushed it closer to the shop
 

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Snowy Rivers

Well-known member
Looking good....
Your machine is a bunch cleaner in the belly than mine was.
Tires look to be in pretty good shape
Still looks like winter there at your place....
 

Snowy Rivers

Well-known member
The Weather this year is very different from the past many many years...
We are still getting rain this morning.....Feels more like April than late June....

Our grass is so tall ....Too wet to really get it all cut....
Our garden is a non starter so far....
 
Been a bit…being summer and all…managed to figure what parts of the hydraulics I’m going to use and how I’m going to plumb it…still in disassembley mode
 
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