In my quest to build the ultimate corporate GM 10.5 inch 14 bolt full float rear axle I want to include a provision to at least warm the oil.
I am going to add a cast aluminum diff cover as one of the many mods, mainly:
because they have fill and drain plugs on them so you can do oil changes with out pulling the diff cover.
can drill and tap additional holes to install equipment
to have the additional holes I add not leak expensive mobil1 gear oil.
to look cool.
I am going to use a Kat's 400 watt, 3/4'' pipe thread tractor engine block heater. 3/4''NPT is the smallest you can get and I know I can make a hole for this and attach it since you only need a drill a 3/4 inch pipe thread tap for 3/4 (applicable part numbers for this engine block heater: GE360, S07090 and 11409)
I need to test this little guy before I install it, 400w over that small of a surface area may get too hot and scorch the oil, so if that happens I will have to devise a way to reduce the voltage to the heater, since this thing is intended to heat coolant, not oil.
I am not going with those stick on heater pads because they suck, but they are better than nothing.
These kat's heaters are pretty neat, they look like you could adapt and install them to heat almost anything.
The GM 14 bolt weights around 550lb, about as much as a V8 engine. But unlike an engine block it only has a few quarts of fluid to warm, so I am going to include a temperature switch. A Reznor Fenwal thermo switch that opens at 150'F to turn off the block heater. (p/n: 08-819133-008)
I have put my IR scanner on differentials after a drive on hot summers day and seen read the cover of a 7.5 and 8.5 GM 10 bolt read at little over 140'F. So turning it off at 150'F on a cold day isn't unreasonable, as soon as the oil get splashed around inside the housing it will cool some.
Additional equipment:
I have pondered adding some kind of external pump and oil filter setup, with possible coolant oil heat exchanger. I have never heard of any one burning one of these up so not going to worry about adding any kind of active cooling. Passive cooling and just the added surface area of the lines and filter setup is likely way more than enough for it to stay with in a safe operating temperature.
Adding a filter would be cool because I would pretty much never need to change the gear oil.
Or I may build the pump filter set up as some kind of stand alone gear oil servicing unit. It stays separate from the vehicle. It would be used by raising up the vehicle, connect the pump and filter to the diff housing using preinstalled fittings, turn on the oil servicer and start the vehicle and put in gear and let it run for a little while to circulate oil and the oil get clean (mobil1 can be up to $17 a quart last time I checked and the 14 bolt uses 2 to 3 quarts of oil).
But there are a few things I don't know.
I don't know what the max temperature on the 14 bolt or any other differential gets when its cold out, I only checked with my IR gun during summer.
I don't know how much heat the 14 bolt puts off. They may never get past being slightly warm or only slightly cool to the touch in winter. Which means that oil is only going to get about as thin as honey.