Printable View
Hello,
How about this to help dissippate the NP200 excess heat?
One could easily braze (either silver braze or silicon bronze) a pocket to the NP200, put two fittings in that pocket and route the return line from the heater to that pocket. That way, the heat would be absorbed by the engine coolant and dissippated by the radiator. Brazing is very easy and there would be no need for a separate pump or cooling circuit.
Any thoughts?
Mikel
Way too much work. My thought was to just screw fittings into the fill and drain plugs, and run them to a little oil cooler with its own fan and a little pump. Then my thought was "I'll just stick a np205 in like everyone else, when I do an engine swap." :)
--Randy
Quote:
Originally Posted by randygar
How is that simpler? :confused:
option a) remove the t-case, drain it, flush the insides, construct a box (probably involving welding or brazing and grinding the edge to a perfect match to the t-case), tap ports or weld bungs to the box, braze the box to the t-case, re-install the t-case (and linkages, dirveshafts, and everything else), run coolant lines, add a large risk of a loss of engine coolant (long hoses under the vehicle, brazing onto a high-stress part,...), refill the gear oil, and not even end up with that good of cooling, conducting all the heat through one patch of the housing, and using relatively hot fluid to try cooling it... (and restricting the flow through your heater, causing it to be less effective)
option b) zip-tie a tranny cooler with built-in fan and thermostat to it and above the crossmember, screw a little oil pump onto that, run wiring to the engine compartment (much easier than coolant hoses), screw two adapters into the t-case, add a couple feet of tranny cooler line and some hose clamps, refill, done.
Or.... wait until you do an engine swap, and put a np205 in at the same time.
--Randy
If you are brazing why not just add cooling fins? My problem with taking coolant back to the t-case is the possibility of trail damage. Right I'm the middle there is a good place to get high centered or just dragged across stuff. You could put it on top but not too much room.
$.02
Water is MUCH more thermally conductive than air. The lines can be routed out of harm's way. That jacket could be put on top of the T/C. Doesn't need to be very thick, maybe 1/4" of space for coolant to flow through.Quote:
Originally Posted by BBM715
The t-case is only filled a third of the way with fluid. It would need to be on the bottom. anywhere else and you're only cooling the air and the stuff slung off the gears to the right spot...
--Randy
When the thing is running, gear oil is being splashed all over, so that doesn't matter. Also, the T/C is a big/thick cast iron box, which is very thermally conductive. Even with no oil slosh, you would be able to dissipate a lot of heat from the top.Quote:
Originally Posted by randygar
And that case is thick. Try it and let us know. Your fab skills dwarf mine so I'd be I terested on how it turns out.
I'm building a NP205/200 hybrid for my 6x6, which will use two of the 200's output bearing assemblies (the most likely sources of the heat). If my 205 starts overheating, this is precisely what I plan on doing.Quote:
Originally Posted by Mikel
I have two things in my favor:
-4.56 gears and 38.5 tires - RPM's should be considerably lower.
-T/C would be bolted to the transmission via a big aluminum (very conductive) adapter, acting as a big heat sink. In a M715, the NP200 sits on its own, with very little to dissipate heat elsewhere.
If you are tearing the cases apart this is easy. Just make sure to clean all of the oil passages and make sure to correctly preload the bearings. The preload numbers are in the manuals. When I rebuilt the NP200 in the M725 every single oil passage was plugged solid, and the preloads were way off. Im almost certain this what causes most NP200's to overheat. Since the rebuild, I haven't seen any heat problems with the 200.
The NP200 internals are too close in resemblance to NP205 internals, and NP205's don't have a problem overheating. Old NP200's with poor oil circulation (or no oil circulation) must be overheating from this problem. Add to the problem trying to spin them at high rates of speeds with 5.88 gearing and 34" tires will certainly cook at 200. The gear ratio you are running with those tires is much better.
Anyways, just my opinion.
Quote:
Originally Posted by rpgdeity
There is probably 99% of the problem, but.........I rebuilt my NP200, hot tanked and thoroughly cleaned the empty case, replaced all the bearings and seals, then set the preload perfectly. It still overheats after any extended driving over 50 MPH.
Now, many members have installed NP205's in stock trucks without doing anything to the 205, which probably had more miles than any 200 ever saw, and instantly eliminated the heat issue. Certainly must be a design difference of some sort.