Front Diff Temperature

[mikallie]

I have just got my temperature gauge workin on my front diff of my western star that has a c15 cat @ 550hp and 46-160 meritor diffs and just cruizing around truck only no trailer it was getting up around 90 degree's c, I am a bit worried what its going to get up to with the trailer on, fully loaded.

Whats the usual range in temperature for these diff? Taking into account what grade oil you are using I guess?

 

[boone315]

Is that 90'F or does that C mean Celsius? if it is 90'F that seems a little cool as far as normal operating temp, but you are b/t and it is winter so maybe that is right,,, if you mean 90'C that seems a little warm, could just mean the gauge is off or you might need to change the fluids. I change mine roughly every two years but I use oil and not synthetic, there are a couple guys on here that can tell you a heck of a lot more then I can.

 

[bigyellowpete]

I wouldn't worry about 90C temps at all. Mine will run that hot bobtail, or with an empty float. If your levels are good, and the oil is less than a couple years old you probably don't have any issues. If you are concerned, get some replacement oil on hand, and pull the brain plug quick and check for chunks of steel on the magnetic ends. You can also pull the fill plug and use a temp probe to check the temp against your gauge to get an idea how accurate it is. An instant read kitchen thermometer will usually work, as the probe is usually about 4" long and should be able to reach the oil if the dif is full.

Mine will run up over 225 F when i am putting torque to them all day, even get up to 250 F some times, which is probably about 125 - 130 C. My metric converter is broken at the moment, so you will have to do the conversions.

You can probably dig up the normal operating temp range from the manufacturers website if you are concerned as well.

 

[mikallie]

Hey thanks guys, yes 90 C for celsius, yes I wonder about the gauge as the needle doesn't go all the way back down to seat right back like the other gauges when cold, it is the middle of summer over here at the moment so reaching 28-30 deg c. What weight oil would you recomment? I have had the truck only 8 months so I am not sure what oil is in it.

 

[bigyellowpete]

I run synthetic gear oil in my diffs over here. It's a little more expensive, but I haul heavy, and it is supposed to handle the heat better.

If it is old school oil, 80w90 is the usual suspect if using mineral oils, if it is synthetic, it is usually 75w90. If you are unsure, give them a drain and fill. It won't hurt them to have new oil in there. Synthetics can go up to about 500,00 miles, or 820,000 km between drain intervals.

 

[2xR]

My front deferential usually runs just a shade cooler than the tranny, and, the rear deferential is always just a shade cooler than the front. There seems to be a natural progression. The closest to the engine is the warmest, and the temps get lower the further away from the engine.

I'm approaching 500,000 and I'm about to change the gear oils. I like to play with the Lucas product demo where you turn the crank and watch the oil climb the gears. Do you reckon it'd be worth the investment to add some to the boxes?

 

[Racer X 69]

Temps as high as 260 degrees F (126 C) should be OK. If it gets at or over 290 F (143 C) I would begin to get concerned, as there might be a bearing or two or three failing.

I would not be concerned about lower temps in the diffs, unless you are running in very cold ambient temps, then you should use something a little lower in viscosity, so it will get to where it needs to be.

The front diff on my truck runs as high as 250 F (121 C) or so in the summer, the rear diff gets to about 200 F (93 C), maybe 210. In the winter running through North Dakota, or up into Winnipeg it barely got to 220/170 F (104/77 C).

And synthetic lubes are better, especially when running at the extreme end of the load envelope. 80-90 gear lube (it is not oil) is the standard to use today, although I think they have something a little thinner for the rigs that run up in Yellowknife and the like in the winter, and something a little heavier for rigs running in the desert oilfields in the Middle East.

I pointed out that gear lube is not "oil" because it is graphite based, not petroleum based like motor oil. And unless you get it hot enough (like way hotter than anything you will see under normal circumstances), gear lube will not burn, where motor oil will.

By the way BYP, excellent idea to use a meat thermometer to check the diff sender. And the lube levels should be full enough that when you remove the fill plug the lube just dribbles out.