WTF-Need help, gear oil/Diff fluid Questions

Alright.

I have searched the googles and the TW.

Can. Not. Get. A. Clear. Answer.

Due to me being cheap and pumped to do a rear and front diff fluid swap in my '03 Taco Dc 4x4 - Limited/TRD with Diff Lock. i saved $30 by buying the O'Reilly "Master Pro"

$30 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 Full Synthetic as opposed to the Lucas 75w-90/Mobil1 full syn 75w-90

What the heck is the difference. Will i mutilate my diff's if i use the Master Pro Vs. Lucas/Mobil1 AHHHHHHH!!! I need TW.com guidance.

Part of me wants to run the GL-5 Master Pro 75W-90 for about 20k miles as a 'crossover' from pure dino 80w-90 to syn 75w-90 and swap to maybe Mobil1 at the 20k mark... but idk. Again. Been reading too many generalities @ bob is the oil guy. Crazy confused. Heard there are additives in the Lucas that i may not want.

Haven't done anything yet 'cept buy the stuff, so i can always return...

Please help.

 

You'll be fine. The diffs aren't very picky on the type of fluid you put in.

 

I've had experiences on axles before when switching to synthetic it made the seals shrink and cause leaking.

 

I switched to synth at 156k miles, Im at 170k now with no problems.

 

And this is why i hate the Internet

Edit* Fyi: this is the stuff i bought: http://www.oreillyauto.com/site/c/detail/MP03/80054.oap?keyword=75w-90

 

synthetic does not "shrink" seals. If anything it cleans out gunk left there by the dino oil which could possible cause leaks. Very unlikely in an axle though.

 

Don't worry about it. However, some synthetic gear oils actually perform better than others. If you go to bobistheoilguy.com, you can read performace data on the different synthetic gear oils. If I remember correctly, Mobil 1 actually performs poorly.

DON'T USE Lucas in your gear oil! It creates a froth and can damage your differential over time. You also need the EP lubricant of the gear oil.

The synthetics flow very well. I like Redline and Amsoil myself. As for weights, anything as thick, or thicker, generally works. It depends on what you use the truck for. A thicker oil can cause more friction and decrease your power slightly, while a thinner oil might not work well for things like towing and shock during a sudden acceleration.

 

Thanks Tylerm - Good info. Going to just slap the Master Pro in the rear and front diffs for now. Re-visit the situation in about 20k miles, see how it looks and go from there.

 

If its GL-5 rated than it meets or exceeds all the ratings that toyota requires.
I run coastal 75-90 because its cheap. Then if I ever get water in the axle I wont end up crying because I had to replace some pricey snake oil that meets the same standards as the "cheap stuff"