Gear grease and differential covers etc ??

[AH64ID]

Understood that the gearset would be warmer than the oil since that is where the heat is being generated along with the bearings. Too much cooling is also relative. Let me go to extremes for example. A differential cooler with an extra 1-gallon diff cover, even with thermostatic control, would be to much for operation in the winter on the North Slope. The same set up might be adequate for racing in the outback in Australia. Wild extremes for sure.
Like I have always said, it's your truck dress it and take it to the dance the way you like it. After I bought the Mag Hytec and installed a temp probe (only one) and experimented with oil level I determined that it ran at least 20 degrees cooler with the stock fill level while towing. To me that pretty much disproves that the Mag Hytec filled to the top level keeps the gearset cooler. Heat is the enemy of longevity. There are several things that can be found to be positives about products Mag Hytec i.e. dipstick, magnets, drainplug. larger surface area offering a slight increase in cooling capability, etc. IMHO if you want to be able to check the fluid level and have the ease of service and have the $250 or so to spend, do it. I have and would not spend the money again for one. I have done my Ben Franklin close on it. In would spend the $250 elsewhere. Probably on a bypass oil filter for the engine.

You say the stock level, but I seem to recall the stock level and the MH level being the same on my 05. Is that not the case on the Dana axles?

You still can’t prove your theory without a second temp probe on the gears. It’s very possible that the higher oil is hotter because it’s pulling more heat from the gears, that would mean hotter oil but cooler gears. (This is the great debate on overfilling a NV5600). I’m not saying you’re wrong, just saying we don’t know.

I also had a bypass on my 05, but neither the MH covers or bypass are on my 18, nor will they be on my 22. I liked them at the time, but I don’t feel there was any return on investment.

 

[bcbender]

This is the great debate on overfilling a NV5600

I overfilled mine to help with lubrication of the rear bearings (allegedly). I ran a temp gauge and it didn't seem to make a difference even with the Fast Coolers, more oil for sure, but in the end the best way to keep it cool was to stay out of 6th and slow down.

 

[Diesel Gunner]

You say the stock level, but I seem to recall the stock level and the MH level being the same on my 05. Is that not the case on the Dana axles?

You still can’t prove your theory without a second temp probe on the gears. It’s very possible that the higher oil is hotter because it’s pulling more heat from the gears, that would mean hotter oil but cooler gears. (This is the great debate on overfilling a NV5600). I’m not saying you’re wrong, just saying we don’t know.

I also had a bypass on my 05, but neither the MH covers or bypass are on my 18, nor will they be on my 22. I liked them at the time, but I don’t feel there was any return on investment.

As far as the fluid level with the MH there is a reference plug on the serial number plate that approximates the factory diff cover plate fluid level. As I remember this was at or very near the lower mark on the dipstick. Don't remember the exact amount of fluid that it took to fill the diff to the upper mark. When I filled to the upper mark the differential ran hotter than when it is filled to the lower mark on the dipstick.

With only having 210K on my truck it is hard to determine ROI. I would think that I would have to compare to other Dana 80's with factory covers and similar service intervals to compare. I have no intention of selling the truck and might be able to share more at a later date before I get the heat treatment, but then that would only be my opinion and hardly scientific. But I will say again that I would probably not spend the money on MH, or any of the other aftermarket jewelry if I could get in the way back machine and do it over again. JMHO.