Today, a friend and I thought we heard something on my 1977 F250. We stopped and found I had difficulty keeping my hand on the differential. It was that warm, after some highway driving (most of my driving around here is 50+ on two lane blacktop).

We stopped by my house and checked, finding the differential full and the lube smelling the way one expects hypoid gear lube to smell. It seems to me the entire cast housing of the Dana 60 (I'm pretty sure that's what it is) was warm.

Not long ago, our '96 Suburban was running hot in the rear diff., especially the pinion housing. I ended up having Mr. Goodwrench rebuild the rear end (191,000 miles on our K2500). I can't afford a rear end rebuild now -- and I'd never hear the end of it , since the wife was unhappy about me buying this $500 truck in the first place.

I'm wondering just how much life I likely have in this rear end.

One other thought: The rear tires are both 31x10.50R-16.5, but they are two different brands. If they are a tiny bit different, am I overworking the spider gears? I think I'll rotate tires, so I have identical brand and size tires on both sides of the rear axle (right now the RR is the "odd" one, the other three are all the same).

I don't have my Raytek temperature "gun" with me, or I'd have the surface temp of that diff to relate to you. Any truckers here who run with differential temp gauges, and might have an answer for me???

Thanks,

Lane

 

The rear differential will run quite warm, more than you can hold your hand on. Running with tires that are not matched will heat the differential badly and wear it out.

Those temp guns are very inaccurate unless they are set up properly. Pull the plug and drop in a thermometer.

 

Thanks, that puts my mind at ease a bit. I will rotate those tires soon. They are the same size and look the same to me, but I know brands vary.

Lane

 

I appreciate your warning on the "temp gun," too. Mine is a RayTek that I picked up still new in box, at a gun show, when it retailed around $200. I see much less expensive ones around these days. In fact, I think I can take it to work (I'm a Hydroelectric Operator) and compare it with some of the expensive equipment we have in the powerhouses.

I've seen lots of fancy monitoring equipment at work, but the one I can count on is: I put my hand on it and it hurt.

I'll keep an eye on the differential. Both axle ends seem cool and aren't leaking. I am trying to keep expenditures on this old truck to a minimum, but I knew it would need a few things. And besides, it's sort of growing on me...

Say, while I'm asking axle questions: The VIN decoder took my axle code and said it left the factory with a locker. I did a little "lawn job" at one of my rentals, and it sure doesn't act like a locker. One wheel spun. Could it just be worn out after all these years?

 

I was down at my shop tonight, and picked up my Raytek infrared thermometer. After driving 18 miles home at highway speed, I slipped underneath and checked the differential. Most was 125-129, with hottest being 135 degrees F. on the surface of the pinion bearing housing.

I guess I'll just check from time to time. As long as it doesn't get worse, I'll live with that.

I am thinking about some Redline gear lube. That might make it run cooler.

Lane

 

Unless the surface emissivity setting is correct for the surface you are "looking" at the readings can vary widely. Drop a thermometer in the lube and set your IR gun to match the temp that is shown. write down the setting that produces the accurate result then you can monitor the temp with the IR gun.

A lube oil change will help. Your diff may be worn out. All of those wear particles are in your oil also...

 

I agree with the statement about surface emissivity, however that value can also vary depending on color paint on the suface, or dirt and grease, or surface rust. If you just want to be within +/- 30* the temp guns will be fine.

 

Oil in diffs starts losing their protection ability at 250 degrees F. working with heavy eqiupment and semis their oils usually run about 225 or lower. Safe zone is up to 250. If it gets hotter than that you have a problem. If that is the case you usually fix it if it just started for fairly cheap.