How hot is too hot. 9" rear diff

[AlanCasida]

I have been making DW shake down drives in my Mustang. I had a 4.30 gear but decided to swap it out for a 4.11 I already had. I needed to swap the front yoke so instead of replacing the crush sleeve and using a torque wrench to set it up I just tightened it snug then gave it about another 1/4 turn on the pinion nut. After taking it on a 60 mile drive I was concerned about the way I tightened it so I got my heat gun out and checked the temp at the pinion support area and found that it was 183 deg. Since I have never checked one before I have no idea if that is hot or not.   

[My427stang]

I can't imagine it is, but it's easy to swap a yoke by pulling the pinion housing if it keeps you up at night.  Wipe the O-ring with a little RTV and slap it right back in after you feel for play, then drag as the bearing preloads

[e philpott]

I had 145 degrees yesterday when checking pinion bearing on a 8.5 Chevy . You should have a solid spacer in place of the crush sleeve for your application

[Katz427]

A while ago, an engineer at Dana told me, 150F + ambient temperature = the upper limit of what they considered an acceptable temperature. Of course synthetic  can handle those temperatures, but regular old gear oil can as well. So your temperatures don't seem excessive.

[gt350hr]

   Alan,
      Temps are relative to gear ratio. A 3-1 will run cooler than your 4.11 because of the higher pinion speed and greater friction from the gear "mesh". "To Me" anything under 200 is safe and temps over that ( like road or oval racing) would simply require an oil cooler set up. When gear oil "oxidizes" ( except synthetics) it gets a "sulpher" like smell to it and also turns VERY dark. You "might " be a touch tight on pinion bearing preload , but that alone is not the cause of the oil temps you are seeing. 4.11 ( 9-37) generates more heat than 4.30 ( 10-43) but is a "stronger " gear deflection wise.
   Randy

[My427stang]

I would like to add again, just with a little more punch

Yes gears make heat, so do bearings as they destroy themselves from too much preload. 

I am not an alarmist, nor do I think you would just hammer the heck out of a pinion nut, but, five 3/8 bolts and the pinion housing comes out as a unit.  Set preload on the pinion bearings and you KNOW you are right.  It won't change gear mesh, setup, or anything else, it just makes sure you have preload right.

Then bolt the pinion housing back in and drive away.

[AlanCasida]

Thanks guys. I am going for another test & tune session tonight and after that I am going to pull the unit and replace the crush sleeve with a spacer and convert to synthetic lube. As usual I am probably over thinking this.