I am on my 3rd set of gears in the LH unit on my twin O/B Sonic.
I am building my own "Lightning" (OMC/BRP's performance housing) LH unit as the factory never produced a LH version. I am using used RH housings that had previously lost a set of gears as thats all I'm finding available.
I just lost the 3rd set and am on my second used housing. I suspect the housings being tweaked when eating their orig set of gears.
Before swallowing the cost of a new OEM housing I'm experimenting w/some changes on this build.
I'm looking at gear lube. I switched to synthetic 75/85 yrs ago and never lost a unit until these lefties and that includes many high HP, 7500 RPM and up motors. I've been using the cheapest synthetics at the auto parts stores which is normally Valvoline.
Now I'm looking at two things.

#1. Upping viscosity from 75/85 - 85/140.

#2. Trying some high zoot fluids like you guys run in your high dollar gear cases. I did a search and read everything on here and it seems you guys like the custom (Neo) blend from the Bravo shop which only comes in 75/85.
I'm not concerned w/the additional drag of the heavier oil, I only want these damn things to survive.

Wouldn't I be wise to go to the 85/140 which Neo offers??

Be interested in any input from you wizards. Also thinking of Cryoing the LH gears.

Thanks Guys!
Gary

I've been using Amsoil 75w110 severe gear in my XR,and all my previous bravos....IMO,75w85 is too thin for a drive pushing some serious power....maybe others will chime in...

I second the AMSOIL 75w-110.

I run amsoil 75 110 but would run the bravo shop blend before the stright neo blend. I dont know why a heavier weight would be better besides the simple fact that the number is larger sounds better.

high horsepower engines will make your drive run hotter...heavier weight wont get as thin,help preventing metal/metal contact....same as running 5w30 in your hi-perf engine

my thinking.

Thicker oil was the way to go back in the day but actually it just more friction/heat, its all in the add pack in the oil that protects the gears and bearings.

Here is something for you to ponder.
Why did nascar start running 0 and 5 weight oils in there engines if the technology wasn't there to support it?

-100

Thats no longer true.
I`m gonna run mantec 80w-90
Mild Thunder also found this place which is local
http://www.leahywolf.com/const.html

Their gearmaster oil is $75 for a 5 gallon pail.. can`t beat that.

Not trying to be a wise guy here, but there are other issues causing the failures. No oil is going to make something wrong all of a sudden right. With that said I'm not a chemist and don't know the why's. But, I do know first of all that gear lube viscosity isn't measured the same as motor oil. A 75 viscosity is not nearly as heavy as you think. I believe it is more like a straight 30 maybe 40 weight motor oil. Second, and more to the point is as mentioned above the add packs. What is important is the oil's shear strength, it's ability to stick to the gears. A good synthetic 75/90 or 75 whatever according to who you use is fine. I do not believe the heavier oil is going to make a difference in its ability to bond on the gear.

I agree. Thicker oils cant help gearcase flex, overheating, poor quality gears, etc.

In class 8 semi trucks, most run 50WT engine oil, or 80W90 in the transmissions, and 80w90 in the rear diff's. Parts go a million miles plus sometimes. Cant say theres no load on those gears hauling 80k + lbs up mountains.