New gauges and rear diff temperature

[THoltz]

I had my Autometer gauges installed at Strictly Diesel shop in Scottsdale Az yesterday. In addition to the usual 3 gauges (EGT, trans temp, and boost) I had a rear differential sending unit and gauge installed on the steering column. I had no idea how hot the rear diff can get. It was 112-114 yesterday in the Phoenix Az area and driving 65 my rear diff finally worked it's way up to 195 F. I have a mag hi-tec cover and run with 6. 5 qts. of Mobil 1 75W140 synthetic. What does everyoby else see for diff temp and am I OK with the 75W140? Thanks!

 

[rotohead]

I get about the same as you. In the winter around here (Lake Tahoe) it won't get much above 100 and the diff temp is most handy when towing. That's when it can get to 200-220 degrees and that's why I use a 75w-140 oil.

 

[ENafziger]

Sounds about right... I'm running Amsoil 80/90 (i think ), and temps usually stay 140 - 150° empty running around town. Towing or extended trips get hotter. I've seen about 215° towing 10k.

--Eric

 

[jkalchik]

Thanks, gents. You've reminded me about something. I'm headed back over to my folks for a week long vacation towards the end of the month. Dad has a 99 3500 2wd gasser that hauls cherries. I'll put an I/R thermometer on the rear diff cover after a 30k lb. gross load.

 

[Radshooter]

You guys got me thinking about adding a rear diff temp gauge now. Our fiver weighs around 17K. How hot is too hot?

 

[rotohead]

I've got my diff sensor hooked up to my auto transmission gauge and switch back and forth with a triple pole, double throw switch from Radio shack. My transmission gauge has temp range markings on it that I go by. There is a 'green' normal range that changes to 'yellow' caution at 240. Above that is a 'red' line at 320. I think things would break anywhere near the 'red' line but I think the 240 mark should be the high mark for the diff.

P. S. I've never seen mine higher than 210-220 towing 8-10k.

 

[THoltz]

The people at Mag Hi-Tech say a synthetic 75W140 has an uper working temperature limit of 280 F.

 

[rotohead]

The people at Mag Hi-Tech say a synthetic 75W140 has an uper working temperature limit of 280 F.

Sounds about right to me. I've got a Dana70 and always wondered if bigger units would be any different in handling temps. I think they all would run about the same.

 

[amsoilman]

The people at Mag Hi-Tech say a synthetic 75W140 has an uper working temperature limit of 280 F.

If you'd like to see a good comprehehsive evaluation of gear lubes, check out this link:



AMSOIL - A Study of Automotive Gear Lubes

 

[Radshooter]

Thanks for the numbers. At least now I will know when to start worrying.

 

[drag racer]

Might want to double check your dipstick in the Mag-Hytec cover - my D80 takes 8 quarts to get a good fill mark. I have gotten as high as 230F towing 10k between Phx-Tucson (not even in the summer) using Mobil 1 75W-90 way back when. After seeing that, I only use Red Line 80W-140 now, and it actually runs slighter warmer throughout the temp. range compared with the 75W-90, but I want that thicker film when she's running that hot.

 

[THoltz]

Might want to double check your dipstick in the Mag-Hytec cover - my D80 takes 8 quarts to get a good fill mark. I have gotten as high as 230F towing 10k between Phx-Tucson (not even in the summer) using Mobil 1 75W-90 way back when. After seeing that, I only use Red Line 80W-140 now, and it actually runs slighter warmer throughout the temp. range compared with the 75W-90, but I want that thicker film when she's running that hot.

I just changed the oil last week. Put in 7 qts plus 8 oz of friction modifier. Dip stick is right in the middle between low and high marks.