how hot do gears get while breaking in?

[GRU]

I just got 3.55s put in my dually this afternoon. Man is it sooo much nicer to drive. Especially with the cummins. The first drive was across town in town traffic for lunch. Maybe two hours it sat in the driveway while we cleaned up and talked. On my way home it was about 10 miles of 55-60 mph highway and 5 miles 35-45 mph country road. After i got home i crawled under and felt the diff cover and i couldnt keep my fingers on it. Im going to guess 150 degree range. I have full synthetic gear lube in it too. Is this normal to be this hot on its first run?

 

[towcat]

mime is usually warm to the touch when not pulling a trailer. maybe yours is due to the gears breaking in.
i like how the 3.55's work behind a Cummins. the time the motor spend in its torque band makes the install work worth it.

 

[PwrSmoke]

They get very hot when breaking in. This is why gear manufacturers recommend no towing and only short hops at high speed until they break in. Short hops, getting the gears hot, then a cooling period brings about a process called work hardening. If you get it too hot, it tends to anneal the gears, making them softer and wear more. You will be broken in within 500 miles or so. Doesn't sound out of the ordinary to me but just go easy on it for 500 miles and you will be fine.

I have diff temp gauges on my trucks, both with 4.10s. At 80F ambient running 65 mpg, diff oil temp stabilizes at 140-160F. The faster you go the hotter and vice versa. The more the load, the hotter and that included hauling or towing, as well as hills or headwinds. Higher gears (3.07, 3.54, etc.) run cooler than lower gears (4.10, 4.56 etc) because tall gears spread the load over more tooth contact

 

[GRU]

Thanks jim thats just what i was hoping to hear. Being a machinist for 14 yrs im rather familiar with work hardening! Unfortunately thats never been a good thing... i got two more 12 mile mixed country and highway trips last night. I need to get these broke in by next wednesday because thursday morning is a 600 mile trip to NC with two IDIs in the bed. Yes calvin i think im really gonna like these gears. Thre will definately be more downshifting when towing but i think i think thatll be ok.

 

[spg]

Were the gears installed with the correct pinion depth, pionion bearing preload and proper backlash settings?

 

[GRU]

My mechanic did it. Not something i was going to tackle. Backlash range is .011 - .016. He had it set at .014. I made the same trip today that i did last night and the diff cover was barely warm this time. Getting ready to do a 70 mile round trip at 60-65 mph with a short break in between. Will see how warm it gets then.

 

[PwrSmoke]

My mechanic did it. Not something i was going to tackle. Backlash range is .011 - .016. He had it set at .014. I made the same trip today that i did last night and the diff cover was barely warm this time. Getting ready to do a 70 mile round trip at 60-65 mph with a short break in between. Will see how warm it gets then.

Heat tapers off fast during break-in, with the first 100 miles or so being the worst. At 1000-1500 miles, best to do a break-in oil change. About 70 percent of the wear metals an axle will generate in the first 70K miles will happen at under 2500 miles. Since there is no filter, it just goes round and round in the axle.