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Thiokol IMP : a pain in the rear (differential)

timh

New member
SUPER Site Supporter
I just bought a Thiokol Imp serial #161 and i found saw dust and shop rags packed in the differential. the clunk that led me to this potential disastershowed up shortly after the previous cashed my check (buyer beware). so- i am stuck with trying to fix the problem. the main drive gear in the differential has a tooth missing . oh what am i to do? i think that ive been had.:puke1:

tim h
 

Snowcat Operations

Active member
SUPER Site Supporter
Saw dust in any transmission is like one of the oldest tricks in the business of used car sales. This is the first I have ever heard it done in a snowcat! In fact doing something like this has absolutely no regards for someones saftey. You can DIE if your snowcat breaks down. In fact I would take this son of a Bitch to court and bring this up. Its not a car where you can call a tow truck. Whats this persons name? Where is his place of business?
 

timh

New member
SUPER Site Supporter
so the story with my imp-- i bought it from a guy getting divorced and may have used it a couple of times. he did nothing to it other than turn the key. i did ask him to buy it back but he declined. before he got it it was bought by a local guy at an auction. i havent been able to talk to him yet but i hope to soon. right after i figured out the problem i was mad at everybody else but after thinking about it im the most to blame for not learning more about the machine. so hopefully things will still work out. i have pics bot i am illiterate so i will wait for wife help before i can post them. wish me luck :toilet: i think that money going down

tim
 

Bobcat

Je Suis Charlie Hebdo
GOLD Site Supporter
What is the straight dope on the C-4 / OC-4 deal? Are they the same? One better than the other? Any drop-in replacements?
 

Teeoster

New member
Sorry to hear of your misfortune Tim, was this the unit form ebay that sold about a month ago?

You know I have no issues with the OC-4 in my unit, but if it ever goes I think I would replace with a cut to size Ford 9 inch axle. They are super common and there is a limitless supply of gear ratios. A standard issue unit is rated for more than 600 hp! Putting an automatic trans and something like a 5.13 ratio would be sweet. Putting some tough disc brakes on the unit should do the trick for steering.

Just a suggestion, but getting rid of the old 500lb oc-4 tractor rearend would probably not be a bad move.
 

mtncrawler

Bronze Member
GOLD Site Supporter
Bobpierce, this is the only place I have ever heard an OC-4 steering differential refered to as a "C-4". Nuttster, where did you get this information that these are really "C-4" units built by Oliver-Clark?
 

Bobcat

Je Suis Charlie Hebdo
GOLD Site Supporter
Somewhere in the forum I saw someone break out the C-4 as a 'Clark' and the OC-4 as an 'Oliver-Clark'. If this is real or imagined, if there is a difference, would be interesting to hear about it for all those poor souls suffering with the 'weak' one.
 

timh

New member
SUPER Site Supporter
this imp was on ebay but it didnt sell. it was yellow with aluminum cab. i called him after and ended up paying 10k for it :pat: talked to petersons and they possibly have a main drive gear. does anyone know how difficult it will be to put it in.
i wish i got smarter as i got older
timh
 

Bobcat

Je Suis Charlie Hebdo
GOLD Site Supporter
Oh, man. So sorry. Can't imagine any Imp going for 10K, with the possible exception of Nutssters!
 

mtncrawler

Bronze Member
GOLD Site Supporter
Bobpierce, can you show a picture of the steering differential on your Christi. For some reason I thought Christi used the wet brake/planetary gear parts of the OC-4 for it's steering. Also, Clark designated this diff as an S 70F-12. Seems like most of the guys having trouble with them own the higher geared Imps. Even though Sprytes have alot more track on the ground the reduction drop axles must make it easier on the OC-4 drive.
 

mtntopper

Back On Track
SUPER Site Supporter
Oh, man. So sorry. Can't imagine any Imp going for 10K, with the possible exception of Nutssters!

Ok Bob, it is time to educate you on Thiokols. Below is one for you that I owned and sold for well above 10K 4 years ago. It is probably worth close to 18K today as it has less than 500 original hours and is in probably better than new condition with the full cab addition.

1974ThiokolImp.jpg
 

Bobcat

Je Suis Charlie Hebdo
GOLD Site Supporter
Bobpierce, can you show a picture of the steering differential on your Christi. For some reason I thought Christi used the wet brake/planetary gear parts of the OC-4 for it's steering. Also, Clark designated this diff as an S 70F-12. Seems like most of the guys having trouble with them own the higher geared Imps. Even though Sprytes have alot more track on the ground the reduction drop axles must make it easier on the OC-4 drive.

Unfortunately, I won't be near my Kristi for a couple of months, but here is the only picture I have. If anyone is in the Boise area and would like to get a better look, I will PM you with instructions to get to it.
 

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    Custom Differential Housing.JPG
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Bobcat

Je Suis Charlie Hebdo
GOLD Site Supporter
OK, Nutssters AND Mtntoppers!:hide:

Ok Bob, it is time to educate you on Thiokols. Below is one for you that I owned and sold for well above 10K 4 years ago. It is probably worth close to 18K today as it has less than 500 original hours and is in probably better than new condition with the full cab addition.
 

timh

New member
SUPER Site Supporter
i dont know if anyone is interested but the story continues-- a new ring gear and pinion runs about 2200$ plus 500 to put in. a rebuilt oc4 runs about 6500 plus labor. a local rebuilder say that often a ring gear tooth breaks from popping the clutch and because it happens so often they are hard to find
 

Snowcat Operations

Active member
SUPER Site Supporter
OUCH! BUT a 10K yard ornament is kinda expensive. $2700 sounds like a hard lesson but will be worth it when its up and running this winter!
 

Teeoster

New member
Tim, if you decide to keep that oc-4 and go with a ring gear, I think you can have just about anything custom made for much less than that. It just seem to me that all this Snow Cat stuff is over priced because of lack of new supply of parts. Try calling Tim from Remote Access, he might have a few spares around for you also.

I really like that unit, I seen it on ebay and thought it had a sweet fab job on the full cab. A new paint job would do it some justice. I have schematics of the OC-4 if you decide to do the work yourself. I went through mine recently and had no issues working on it.
 

Mainer

Boggie likes our museum
SUPER Site Supporter
i dont know if anyone is interested but the story continues-- a new ring gear and pinion runs about 2200$ plus 500 to put in. a rebuilt oc4 runs about 6500 plus labor. a local rebuilder say that often a ring gear tooth breaks from popping the clutch and because it happens so often they are hard to find

Insane. I also believe that this whole shortage of parts issue is folks being opportunistic. Yes, there is a shortage but if you compare similar shortages to vintage cars, etc... they are no where near as nasty (not in all instances but many). I think a piece can be customized more reasonably than those prices.

There was a guy that bought a Thiokol 4T10 then replaced the twin drive shaft with a Bombardier differential. I believe it was the 'Snow Toaster' rebuild. So, obviously customization was required however if a person can find a whole diff from a newer machine or find a 'deal' then it may be possible to do something completely different and end up with a more reliable system for either less or maybe the same money. At least it may be more robust than something that is so sensitive that popping the clutch creates internal chaos and destruction.

Just food for thought.
 
New here to the snowcat world with a 67 1200A with a C-4. Looking for parts and manuals for the rebuild of the century, I found Landis Zimmerman in PA with Zimmerman Oliver and Cletrac that is still offering manuals, parts and repair service. Landis can be contacted at (717)738-2573 or http://www.olivercletrac.com/contact.html. His quoted price today for a R/P is $1550.

Does anyone have a source for the (2) bearing spacers on the main drive axle. The first rides between the axle O/B bearing and the 36 tooth gear and the second rides the spine side thats against the drop box bearing?
 

timh

New member
SUPER Site Supporter
yea cant afford to fix it cant afford non to fix it. im still looking for a less expensive part but no luck yet. i just talked to the person who rebuilt the cab and he didnt mess with the differential so the people before him were the culprits. so looking for ring gear and pinion. imps around utah are going for 8k for iffy cat to 16 for re worked.
 

nutsster

Member
I've been away from the forum for a while and came across this topic. What a shame that there are such dishonest people! :2gunsfiri
The thing you must be careful about on the Clark -4 or any differential for that matter, is what damage did the missing tooth do. Steve, at Peterson's told me that the tooth will almost always go through the gears and cause the case to get cracked. Usually the problem is much greater than just a broken gear.
If it were mine, I would take it to Peterson's (removed from the chassis to save $$$) and have them take a good look at it. Have it rebuilt the right way by real experienced mechanics, then take good care of it. I know it will cost some cash, but it will increase the value too.

I went through this with my 1402 last winter. Someone tried to piece it together with "repaired" parts. I went as far as having to get a new case. :4_11_9:
But today I have a very nice cat, that is very dependable.:thumb:

Steve said that Peterson's have looked at some Imps to buy for resale, but have stayed away from some due to the risk of a problem in the rear end. After my experiences, I would not give top dollar for one unless it has been closely checked out or recently rebuilt. If that's not the case then you have to steal it to cover your risk.
 
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Snowcat Pat

Active member
Ive been talking on the phone with some of you about this OC-4 or S70F-12 if you prefer and knew from years ago there was a connection with it and the Oliver Cletrac HG, OC-3 and OC-4 crawlers. I'de seen the parts and was sure that they were the same. I didn't check any further 'cause I moved over to the OC-12 and the M-29.

So I'm searching today and found Zimmerman Oliver Cletrac in Ephrata PA www.olivercletrac.com 717-738-2573 and rushed over here to tell you guys and your already ahead of me. I think you might have found your alternate source. I hope they fit 'cause lots of old Sprytes and Imps need spares. I'm a rebuilder and the high price of parts is always difficult to overcome. Good work.

This is an interesting link. Check the forum, at least one of our friends is there :)

http://www.cletrac.org/

Pat Foster
Wallace Idaho
 
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MNoutdoors RIP

Gone But Not Forgotten
GOLD Site Supporter
yea cant afford to fix it cant afford non to fix it. im still looking for a less expensive part but no luck yet. i just talked to the person who rebuilt the cab and he didnt mess with the differential so the people before him were the culprits. so looking for ring gear and pinion. imps around utah are going for 8k for iffy cat to 16 for re worked.

If you wish to change to the OC12 with the final drives we have several of them here and could offer you a good price.

Sorry about your differential

Brad @ Minnesota Outdoors
www.mn-outdoors.com
 

timh

New member
SUPER Site Supporter
does anyone know how difficult it is to change from an oc4 to a 12? and will the 4cylinder have enough ponies to handle it?:confused2:
timh
 
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