Rear ends run pretty hot, the hypoid gearing generates a lot of load induced heat. For long distance road and track racing a pump is employed to route rear end lube through a cooler.
Bogie
Bogie
Operating temperature of rearend
Can anyone tell me what should be the operating temperature of the 12 bolt rearend on my 69 camaro, I'm running 3.73 gears and used a Strange Engineering pinion bearing preload assembly instead of a crush sleeve. New bearings and I double and triple checked the preload, backlash, etc. I've never really checked the operating temperature of rearend before but mine is quite hot to the touch, 160 degrees with my infared gun, I know there is residual heat from the exhaust that is tucked in there pretty close but I wasn't expecting it to be this hot.
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I have checked a few at operating temp and found them to be 120 to 140F
That's good to know maybe mine is ok then.
Anything under 250°F or so is great. It also depends on the type of diff and how hard you're driving it.
Back in my racing days, we logged or even had live telemetry for diff lube temp. With certain types of limited slip units, that's one of the fastest responding readings to track conditions. We could literally see the car going through corners and down the straights by the changes in the diff lube temp. The temperature would spike quickly in the turns, and it would cool slowly but significantly on the straights. On a high powered GT car I worked on, we saw between 220°F and 300°F at different parts of the track. Ours had a cooler for the diff lube with a thermostatic fan that cut on at 240°F IIRC. And with the design of the diff we had, with the drain plug lined up with the ring gear and getting a lot of movement in the lube at the drain plug, we didn't use a pump. Our gears would pump the lube through the cooler loop. The drain plug was plumbed to feed the cooler, and the fill plug was plumbed for the return.
Back in my racing days, we logged or even had live telemetry for diff lube temp. With certain types of limited slip units, that's one of the fastest responding readings to track conditions. We could literally see the car going through corners and down the straights by the changes in the diff lube temp. The temperature would spike quickly in the turns, and it would cool slowly but significantly on the straights. On a high powered GT car I worked on, we saw between 220°F and 300°F at different parts of the track. Ours had a cooler for the diff lube with a thermostatic fan that cut on at 240°F IIRC. And with the design of the diff we had, with the drain plug lined up with the ring gear and getting a lot of movement in the lube at the drain plug, we didn't use a pump. Our gears would pump the lube through the cooler loop. The drain plug was plumbed to feed the cooler, and the fill plug was plumbed for the return.
Rule of thumb on the street is 90 - 100 Degrees F higher than ambient air temp.
Lots of good information here, nice to know that mine is within range.
If you have a cover with a fill and drain port you can run a line from the fill to an oil coolier then back to the drain port. This increases fluid capacity while allowing a coolier to be in open air below the axle tube.
Your not increasing fluid level in the diff just cooling via convection. It is more then enough for a street application.
The only downside is that the lines and coolier need to be level with or perferably below the axletube (between or below the fill/drain ports) which can lead to the lines snagging things or the coolier being crushed.
Your not increasing fluid level in the diff just cooling via convection. It is more then enough for a street application.
The only downside is that the lines and coolier need to be level with or perferably below the axletube (between or below the fill/drain ports) which can lead to the lines snagging things or the coolier being crushed.
Interesting stuff, with that kind of heat being produced being an indicator of power being soaked up you can imagine why mfr's might put in the smallest rear ends they can get away with. A clutch-type posi would certainly add to it. I once did an all-day drive through mountains in my 12-bolt-posi El Camino and at the end the diff was grabby and clunking around corners and disassembly showed clutch plates burned black and blue, I can only guess how hot it must have gotten.
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