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OC-12 parts

fischerrc4

New member
Anyone have any OC-12 Differential Thrust Washers, or Specfications for Manufacture? Peterson Equipment is Out of Stock. Need Some ASAP.
 

Snowcat Pat

Active member
Hi fischerrc4,
I got your PM.
There are lots of washers in the OC-12, including "Morty's death washers"
I probably have what you want.
Post here with photo(best) or call 208-556-0153
-Pat
 

fischerrc4

New member
Hi Pat,
I will be more exact. I'm looking for the Compensating Case-Long Gear-Thrust Washers. I belive it takes about 12 of them? I can get you photos later today if needed. Some of mine are worn, and missing.
Thanks
 

Snowcat Pat

Active member
I spoke with fischerrc4 but just to follow up, the LMC part number for those is 1209162 item #20 in the manual. It says qty. 6 but there are actually 12. I buy them at Fastenall they have 2 thicknesses of 1 inch machinery bushings.
18ga. is #1133444 and 14ga. is #1133445
I select the thickness to adjust the end play of the gears.
Make sure the end of the woodruff key is not grinding into your new washers, the keys usually need to be shortened a little.
Its good idea to deburr/round off the ends of the internal compensating pinion gear teeth to prevent them from gouging the inside of the compensator case. I use a Dremel with a conical stone and put an old comp. pinion bushing on the shaft to protect it from fumbles. Just break the burr/edge, on the end with the tapered shaft, it makes a big difference.
On my last rebuild it took hours to build up an re-machine the case where the gears hogged out the metal.
-Pat
 

fischerrc4

New member
Hi Pat,
Do you have any Compensating Case Bushings (2) ? The part # 1209192 is what I am looking for.
Thanks,
Steve
 

Snowcat Pat

Active member
Hi Steve, My manual shows part # 1209192 is the cover gasket.
The compensating case bushings are part # 1209141 in my book and yes we have them. $30 each
-Pat
 

fischerrc4

New member
Hi Pat,
You are Correct, My mistake! I will need (2) for sure. I also am looking for Part # 1209159 spacer washers. It calls for (2), but it looks like it needs (4). Seems like the 2 on the inside only is what my drawings indicate, but 4 looks better to me? Could you tell me what the Brass Bushing to shaft specfications are, and the general bushing to shaft specfications thruout the differential.
Shoot me a total for the parts, and an address, and I will get it on the way.
Thanks
 

Snowcat Pat

Active member
1209159...Morty's death washers... have likely caused as many blown diffs as broken brake band anchor pins (01540-213). I don't use the stock washer so I don't have any new ones but lots of used, you can have them. If you look they don't fit right and wear fast eventually they split and wreak havoc in there. I make custom fitted bronze washers for that area, expensive but worth it. Also, the factory set end play on the brake drum bushing varies huge.

New clearance for the compensating pinion bushings is .004, when they get loose the pinion gear teeth get gouged.

I'll check my 1979 DMC tracked vehicle service seminar manual that has some wear specs in it.

It must be time to post some photos, at 24 kbs it will take a while, but I'll try to get to that today. This thread might be a good place for rebuild pics. Please be patient.

-Pat
 

fischerrc4

New member
Hi Pat,
I am intrested in your custom washers. Does it take (2) or (4)? I will be taking lots of photos, and video to post when I start assembly. I have roller bearings for my drop boxes that are rare, I am told. Your tips are greatly appreciated.
Thanks
 

Snowcat Pat

Active member
Lets back up a bit to the comp pinion washers, and their woodruff keys.

The first pic shows the key sticking out so as to gouge the washer.

The second shows the end of the key I have ground a bit shorter.

The third shows the key end is not there to gouge the washer anymore.

The washers are selected from the two sizes to match up the end play (.010 minimum to about .030 max) of the comp pinions as installed.

Next post will be the 1209195 washers. You will need two.

I've asked Nancy to scan the Critical Measurements List in for us to download to the forum.

-Pat
 

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Snowcat Pat

Active member
Critical Measurements List.

can't read bmp, we will try something else later.

-Pat
 

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fischerrc4

New member
Hi Pat,
I was still unclear about the internal compensating gear spacer/washers.
It shows (2) 1209159. So you put (2) of your brass washer/spacers on the inside, and metal to metal on the outside of the internal gears?
I expect more parts in today, and will contact you soon for the remainder.
Thanks Alot
 

Snowcat Pat

Active member
A re-scan of the Critical Measurements List

Next the bronze washers.

If no one minds can this thread be moved to the Thiokol/LMC/DMC Technical Issues section?

-Pat
 

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Snowcat Pat

Active member
These are the stock 1209159 brake drum washers. Depending on how much end play there is in the drum bushing affects how long these washers will last before they split. More end play + faster wear. In any case they wear unevenly and are one of the sources of metal particles on the magnetic plugs. Because of the radius of the journal the washer has to have a too large of inside diameter so the edge of the washer gets wedged between the radius of the journal and the chamfer that is on the drum gear to clear said radius. Usually starts by bending the washer and gets worse from there. The factory set end play varies huge on the journal length but not the drum gear.

It seems that diffs that have no oil filter tend to get rebuilt more often and the stock washer get replaced before too many hours. The filtered diffs go so long between rebuilds the the washer can and does wear through and split out. When it does that it forms a perfect ramp for any of the ball bearings to get jammed on, which will stop rotation of that ball set and that will crash the ball cage. Then the balls fall out and you can guess the rest.

There is no washer on the outer ends of the brake drum. Both the steering drum gear (1209167) and the the spacing washer (1209144) are hardened steel and wear remarkably well.
 

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Snowcat Pat

Active member
The pics below are the gear side of things. You can see the chamfer in the bore to clear the radius or as some call it the fillet, of the drum gear journal (shown in the previous post). The washer has to clear this area also and has to be oversize. Without a washer the gear face grinds into the compensator cover casting at the base of the drum journal. These also have new drum gear bushings installed and machined.

-Pat
 

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Snowcat Pat

Active member
This is how I sleep at night rebuilding OC-12's for others. A little extra work but so is replacing a broken drop box on a mountainside. I just make a bronze washer that fits.

Thats all for today, I have more photo sorting to do, I'll try to show the compensator pinion problem next.

-Pat
 

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fischerrc4

New member
Outstanding photos, and explanation Pat. After receiving my parts on friday, and seeing your photos. looks like I need 2 of your washers for sure. I am still looking for the 12 dimple bushings, part # 1209142, and the spacer washers part # 1209159, for the internal compensating gears.
I will take assembly photos of my project to post when I round up all parts.Thanks for the great photos!
 

Snowcat Pat

Active member
I mentioned the that the compensating internal pinions have a sharp edge that gouges the compensating case cover.

The first pic shows a pinion in excellent condition. You can see the sharp corner on the end of each gear tooth.

Second pic shows the pinions bearing surface covered by an old bushing to protect it from the stone. This job goes really fast and easy with the high speed Dremel. Just a touch to break the edge.

Third pic its all done. 5 more to do.

Fourth pic is a comp cover that has had an unhappy life in several machines.

Fifth pic is the wear pattern from the pinion end when things get loose. Usually only three holes on each cover show wear but the cover has been rotated during a previous rebuild. Things are made worse by the machining of a wider groove on the comp cover face. Only the V- groove is supposed to be there. Someone widened it presumably to clear the axle gear teeth but it accelerated the pinion hole wear. Its better to bevel the side of the gear teeth ever so slightly and install new comp cover bushings and spacer washers.

The six internal comp pinion gears get more wear than any other gears in the diff. When the gear teeth get scalloped from high hours the gears pairs tend to push away from each other into the comp cover face. When the 12 bushings get loose the gear tooth wear accelerates. When these two conditions exist in running snowcat you can hear the gears growl when turning. Sort of a muffled ratchet sound.

-Pat
 

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fischerrc4

New member
Do you have any photos of the large internal compensating gears with spacer washers, and the washer thickness?
You have very valuable rebuilding info.
Thanks
 

Snowcat Pat

Active member
I think your asking about 1209156 some call it the compensator gear some call it the axle gear, the manual calls it a gear but all the same thing. 1209159 would be the spacer washer.

I put the cases together with the gears but without the old washers and measure each of the gears end play, usually its about about .040. Then part off new larger o.d.washers to custom thickness about .035, I shoot for .005 minimum end play when assembled with the washers. Only one washer per gear on the inside journal against the comp case bore.

I'm still sorting pics, don't know if I have any pics of the washers. The easy way is to buy them from Peterson. I'm not sure of the thickness, about .020 as I remember.

How does one place text between the pics in a forum thread? Glad you like the info, looks like a few others are viewing the pics so I'll keep going with it. Its getting easier, kind of fun too.

-Pat
 

fischerrc4

New member
Peterson does not have, or plan to have the washers, but I was going to use your method to shim mine. I plan on using timken hardened thrust races, part# TRA-3446. Bore them .050" to fit, and see where I'm at. They come in .030" thickness. If it's too tight, I'll have to come up with a new plan.
 

Snowcat Operations

Active member
SUPER Site Supporter
Once again Snowcat Pat shows us his excellence! And I bet people thought you were joking about dreaming of building OC12s!
 

Snowcat Operations

Active member
SUPER Site Supporter
FISCHERRC4
Ask about his stainless steel slave brake cylinders for the OC12! I now have two sets of them on my OC12s. I will NEVER have any other!
 

fischerrc4

New member
When mine are shot, they will be replaced with the Stainless Versions for sure. My Cat will only get the Best, price is not an option, Quality is number 1.
 

Snowcat Pat

Active member
Snowcat Ops here is the speed vs gear ratios chart as promised.

Thanks for the praise! It's my pleasure to share this info. So many old timers have retired the knowledge is getting lost. I just hope to preserve it for future Thiokol enthusiasts.

More to come.

-Pat

It just now worked for me but if you cant see the chart let me know.
 

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