How hot does your rear end run?

turtlevette

turtlevette

The Turdle
Joined
Mar 24, 2008
Messages
1,492
Location
Marshfield, MA
On my trip to Niagara, i took the temp of my rear end with the IR gun.

It was running about 210. That seems to be a bit hot for just cruising down the highway.

That pinion is screaming though at about 4500 rpm with the 4:56 gear.
 
Depends on the heat level of the green chile's consumed.

Seriously though, I've never IR'd the diff on my '73. I'll try to remember to do it the next time I'm out in it.

DC
 
turtlevette said:
On my trip to Niagara, i took the temp of my rear end with the IR gun.

It was running about 210. That seems to be a bit hot for just cruising down the highway.

That pinion is screaming though at about 4500 rpm with the 4:56 gear.
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Oh lord so many ways to twist & pervert this one.

Don't remember what trans & thus ratios you're running---but a 4point 5fucking 6 rear end on the highway? No matter what kind of OD gears your're running in the trans & thus engine RPMs, you're still spinning that diff at exhorbitant speeds not meant for longevity....I'd be one hot mofo myself if I had to spin like that for any length of time.
But I got no clue and 210 doesn't seem too hot to a guy who used to routinely cook steaks & burritos on the cylinder heads while traveling. But I do not care for RPMs of any type, anywhere, so that's where I get 'concerned'---
 
I frequently check the rotor and caliper temps after a track session, but never have bothered to check the rear end. I'll have to try to remember to do that next time. I've got the aluminum batwing on the '69, and I've noticed that thing sure does conduct some heat from the center section.
 
69427 said:
I frequently check the rotor and caliper temps after a track session, but never have bothered to check the rear end. I'll have to try to remember to do that next time. I've got the aluminum batwing on the '69, and I've noticed that thing sure does conduct some heat from the center section.
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check your cover bolts for torque from time to time and #271 on them.
 
turtlevette said:
On my trip to Niagara, i took the temp of my rear end with the IR gun.

It was running about 210. That seems to be a bit hot for just cruising down the highway.

That pinion is screaming though at about 4500 rpm with the 4:56 gear.
Click to expand...

I took notes somewhere on a 373 I build I think it was in the 150-180 range but I could be wrong. I'll see if I can find the notes when I get in the shop.
 
4500 rpm at highway cruise speed ?? wow.... I'm at 2000rpm at 70mph..... :smash:

good thing about running the diff at 210 is that you're boiling any moisture that might be in there off LOL
:smash:
 
turtlevette said:
69427 said:
I frequently check the rotor and caliper temps after a track session, but never have bothered to check the rear end..
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You did actually tell us 210-230 after a track session at Gingerman with an IR gun.
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Damn Turtle, you keep better records on my car than I do. :amused:

Thanks. :thumbs:
 
GTR1999 said:
New 373 iron diff, broken in with 500+ miles, 78*F ambient temp, 30 minute combination drive = 158*F
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:evil: That's one thing that bugs me, 78 ambient, say in the shade behind your house....

out on the highway coming off that assfault in sunlight/traffic/off freeway ramps engines pumping out heat like a mofo, especially here in Florida, that ambient gotta be 120f....sure as hell feels like it....can't walk barefooted on the assfault...:hissyfit:......I bet those diffy's running much closer to 250f easy....

got a question, I know that in my old Muncie 4 speed, I took out the old gear oil and put in 30 weight synthetic engine oil....and it shifted SO much easier, it felt like a new car.....

which makes me wonder about doing something similar to the diffy in my '72....any comments on that???:confused:
 
GTR1999 said:
New 373 iron diff, broken in with 500+ miles, 78*F ambient temp, 30 minute combination drive = 158*F
Click to expand...

Thanks Gary. We all have these cheapo IR guns now. It'd be nice to put together some more data if others want to take temps when they're out.

When i bought this current diff for 100 bucks the ring gear bolts were sheared and the posi case bearing on one side was damaged. I zip tied the shims on each side together but didn't label them. When reassembing i put the the shims back in the configuration where there was less pinion lash. I should have painted the ring gear to get a pattern, but you know me. The 456 ring gear has a spacer to fit the 3 series carrier. I gooped up the case spacer gear and bolts with locktite red.

Its been holding together for 10 years and about 100K miles so it can't be that far off. As these things wear will the pattern get better or worse?

I would think better because the pinion and ring are wearing to mate better?
 
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Gene,
I would not run 30 wt in the diff. There is always debate on who has the best oil for the diff, I just keep using and recommending what has been working for me, Lucas 85-140 and (1) bottle of GM additive.

Interestingly, the test of the running temp was made in FL but I agree it will change with conditions.

Turtle,
What can I say, you took that diff and put it together opposite of what I would have done and it's been running ok! I don't like the RG spacer as many have caused the RG bolts to loosen and back out but that #271 is pretty good stuff. If you want my recommendation, I would remove the diff when you can and go through it the right way and see but how can I argue about that when you just drove 500 miles on it!:crutches:
 
GTR1999 said:
Gene,
I would not run 30 wt in the diff. There is always debate on who has the best oil for the diff, I just keep using and recommending what has been working for me, Lucas 85-140 and (1) bottle of GM additive.

Interestingly, the test of the running temp was made in FL but I agree it will change with conditions.

Turtle,
What can I say, you took that diff and put it together opposite of what I would have done and it's been running ok! I don't like the RG spacer as many have caused the RG bolts to loosen and back out but that #271 is pretty good stuff. If you want my recommendation, I would remove the diff when you can and go through it the right way and see but how can I argue about that when you just drove 500 miles on it!:crutches:
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Gary, I not so sure about diffy's....and hate betting bux on a guess, but in the case of the Muncie, I had heard at the time, that the later stick shifts ran auto trans fluid, and spend less time creating heat from thick oils....

I would IMAGINE that diffy's would do the same, ASSuming the posi additive...

is that the same additive they put in ATF?? maybe Ford F??

:crutches:
 
Get the specs on whatever oil you're running and see what they say. If the oil starts to break down at 275* and you're seeing 210* I'd say no deal. The oil breakdown point is what I'd be worried about. Some of the OTR trucks I drove way back when would run in the 190-200 range, but we're talking about a 14" ring gear and anywhere from a 3.70 to a 6.17 ratio too. And 2-3 GALLONS of oil.
 
TimAT said:
Get the specs on whatever oil you're running and see what they say. If the oil starts to break down at 275* and you're seeing 210* I'd say no deal. The oil breakdown point is what I'd be worried about. Some of the OTR trucks I drove way back when would run in the 190-200 range, but we're talking about a 14" ring gear and anywhere from a 3.70 to a 6.17 ratio too. And 2-3 GALLONS of oil.
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Only 14"? seems kind of small, AFAIK, that was the size of the diffy ring gear in a old state roads dept extended cab long bed pickup a buddy bought off some auction....freeking thing the length of my driveway....he bought a locker for it, and I helped install it....jeez almost 20 years ago....:crutches:
 
Probably is bigger, damn thing is heavy as h888, trying to balance it on a floor jack under the truck to stab it back in.
 
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