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IMP C4 Cooler??

jp11

New member
I've been rolling an idea around in my head for a few weeks. I spoke today with Mr Zimmerman that rebuilds lots of rear ends from the Cletrac dozers (same part as our IMP rear end but with a flipped ring gear) and is rebuilding mine.

My theory is thus:

The dozer version of these machines rarely ever has an issue with the rear end. According to Mr Z. the units only turn at a maximum of about 1800 engine RPM input. Of course.. dozer operations are lots of back and forth, much slower than a snowcat, and rarely ever just go and go and go in one direction, like say a groomer pulling a drag.

By design.. this unit seems to be cooled by fluid, mass of the iron housing, and I would guess the idea that with it's low ground clearance, dragging it thru the snow. That would make those using it for non pulling chores have better results. Cabin access guys would be going thru deeper snow more often.

A guy like me, who would be grooming trails, would be going out after the air has been knocked from the snow. Very little snow 'flying' around to cool the rear end. The duty would be pulling, and generating more heat. Likely way more turns grooming trails then just heading out for a cabin.

SO....

I've made up my mind to install a rear end cooler on my cat. I'll "T" into the fill port for the fluid (this will make me purposefully run an inch or two over on my fluid level, not all that uncommon I guess) Top port in the T will be used for a temperature sensor. Side port will go to a self priming, gear type pump. I've seen several that are used for racing applications. 3gpm or so is the flow. I figure while using the fill port as a input to pump.. if I had a catastrophic hose blowout on a line on the pressure side... The pump will starve and the rear end will still have it's fluid in the pan like it always did.

After the pump, I'll install a spin on filter. Mr. Z said while the fluid stays pretty clean (assuming he said a good shift boot on the unit) he said the dirty material from brake band breakdown might not cooperate with my oil pump.

After the filter I'll run back to an access plug on top of the unit. Mr. Z was concerned that I make sure I have this cooler 'switched' so I can let the fluid warm up to start out.

He's not much of a 'synthetic guy' but he did say MANY of the issues he's seen with these units is from improper oil or water infiltration. He stressed that GL5 spec oil should NOT be used due to many bronze seals used in the construction of the C4. I looked up the amsoil power shift fluid 50w. Discovered it's a GL1 fluid. He says all should be well.

Now.. is all of this overkill? Probably! but.. if I can spend a few hundred dollars 'insurance' to protect what is the most costly part to fix or replace on the cat. I think it's worth it.

Ideas? Comments? Criticism?

JP
 

Steinbruchsoldat

New member
Sounds like a great idea. Build something like this for a high hp supra rearend and it worked pretty good.

I'd incorporate a thermostat, so the oil only gets cooled if its to hot. You don't want it to be cooled to much, so it doesn't reach working temperature.

You could also use a oil/water heat exchanger, thats probably what i would do. This is great for bringing the oil up to working temperature fast and then keeps it constant. This has been eine for automatic transmissions for a long time, shouldn't be bad for a rearend either.
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
the problem is the oc differentials really shouldn't run much above 150 degrees the engine should be around 180
 

Steinbruchsoldat

New member
What's the reason for that? The oil?

Either way, you don't want it to be cooled to much, put in a thermostat like for the remote engine oil coolers.
 

jp11

New member
Hmmm.. you mean a thermostat on a bypass line around the cooler? Or a thermostat that would electrically turn the pump on and off?

JP
 

Steinbruchsoldat

New member
You could probably use a thermal switch like on a radiator to turn the pump on and off.

Bypass line only would make sense if the pump would be running all the time, like driven by the engine.
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
What's the reason for that? The oil?

Either way, you don't want it to be cooled to much, put in a thermostat like for the remote engine oil coolers.

I believe it is viscosity issues I was told if the oil gets up to 180 degrees the life of the differential will be short and normal temp should be around 150. I think the best way to do it would be a full flow oil cooler with a thermostatic fan, when the temp rises the fan will come on ,and if the cooler is mounted sideways there would be no air flow through it until the fan kicks on. the oil isn't like engine oil it's just a splash system in the diff there should be no need to warm it up any quicker. besides once you start using the brakes it's getting hot plenty quick.
 

Steinbruchsoldat

New member
Not sure if it´s needed, but if i`d do something like this, i`d do it right.

I`d use a two stage temperature switch, first stage to turn on the oil pump, second stage to turn on the fan.

No gear system likes temperature changes, so if you go through the hassle to add that cooler, do it the way it`s the best for the differential.

Probably overkill, but i just like to do that stuff like i learned it. Probably my english is not good enough to explain what i really want to day...
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
your explaining it right and nothing wrong with how you suggest to do it other than the cost involved Thiokol when they did it used a scavenging pump run off a pulley on the drive shaft that pushed the oil to the front though a cooler and back to the gearbox. if the engineers felt this was good enough a scavenging pump running all the time will work fine for me. that said a switch added to an electric drive pump would stretch the life of the pump and remove a load from the electrical system until it was needed.
 

redsqwrl

Bronze Member
GOLD Site Supporter
Jp do you have a hydraulic pump on your imp?

the 2100 that i have has a oil to oil pump hooked up. Pretty sure it runs all the time on a return line. Hydraulic oil runs the motor which is direct coupled to another pump which has the rear diff oil in it. I am not sure if the diff oil ever went to the cooler in front. If you search Thiokol 2100 diff cooling the thread that I sourced my hyd diagram from will pop up. there is some good discussion from snowcat pat on that thread.
Have him fab up something for you.

Mike
 

JimVT

Bronze Member
GOLD Site Supporter
bombi run a belt off the drive line to a small pump like a power steering pump.. it had a oil cooler with a large filter the flowed into the gearbox right on top of the gears.
it only worked when you were moving.
jim
 

jp11

New member
No pump on my imp. Fluid just sits in the C4. relies on splashing and iron for cooling.

going with a pump. I guess for now.. I'll use a toggle switch and a gauge and see how it works. I've got a buddy who is an electrical engineer. He starting talking about switching and such.. but FOR NOW.. I guess I'll monitor what the temps run. I guess I'll switch the pump and the fan separate... see how it performs.

JP
 
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