The Stovebolt Site Forums The Shop Area General Truck Talk hot differential

Here's a general question - I'm building a circular sawmill, the driver is a Detroit Diesel 3-71, the blade will be driven by shafts through a Ford 9" rear end (3.25:1 ratio, @ 1800 rpm the blade will turn at ~550 rpm.) Here is the question, with no load, the differential gets hot (almost too warm to keep my hand on it) after spinning for 1/2 hour or so. Do I have a problem? I don't ever feel the differential on my vehicles, so I'm not sure if I should worry or not. Any opinions? Thanks,
Ray

I think that is fairly normal. being a ferd 9 inch, you should be able to replace the center section if you end up burning it up. not a bad idea to have another one around. what gear oil are you using?

WOW, a circle saw...you must have kerf to spare.

Although I have never felt a differential after running, I would say yours might be too hot.

I can't imagine that it was engineered to rely on air passing over for cooling.

If your mill is being driven by one axle, what have you done to the other axle? Restricting its rotation might create extra heat in the spider gears.

The normal scenario would be for both axles to turn about the same speed, but utilizing it as you are, I don't know how that would be possible.

What are you cutting, and what diameter is the saw? Your critical speed will be FPM on the rim of the saw, not RPM. Good luck.

Stuart

You'ld be surprized at how hot a diff can get, even at relativly low speeds. I wouldn't be too concerned, unless there seems to be ant odd noises or smoke coming from it. Something you could do is to run a pump from the diff to a small oil cooler. You could run it from the pinion yoke. They run a setup like this on racecars, all the Nascar racers have this. Also make sure that you have the lube level at the correct amount, maybe even use a synthetic like Lucas or Royal Purple.

runnin a rear end with one side blocked or braked will make it run a little warmer... if ya can hold ur hand on it,,and its a tad uncomfortable thats not too hot... if ya cant touch it,,then its pretty warm...if it will fry spit..then its real hot... if it glows in the dark then thats tooooooo hot...LOL.. A rear end pullin a load on a warm day can get to where its almost uncomfortable to touch...
im sure ya know that rpm is real critical on that circular blade. circular blades are hammered to run at a certain rpm and not much tolerance or it will start wobblin..then cut crooked, but im sure ya know all that...but that old detroit outta with the governor right keep it pretty constant if its geared right.. miss my sawmill...had one years ago..and cut a plenty of wobble crooked boards settin it up...LOL... next time im goin with a bandsaw....

Thanks guys,
I filled it with some old 90 wt gear lube, I assume that's ok. A friend took off one axle, installed a "mini-spool" to lock the gears and removed the spider gears. The saw blade was set up to run off a tractor pto, or 540 rpm, so 550 should be ok.
Yeah Fatweed, if I was to do it again, I'd likely get a bandsaw. Would have paid more, but would have been cutting for a couple years already, instead of still building on it. On the other hand, I don't have much time to hang around the bars, so maybe it has its benefits. Thanks again.
Ray

send us some pics! maybe even put it in the gallery. sounds pretty cool!