Re: Thinking of Dual Range® Auxiliary Transmissions from US Gear
The USG unit is a very well made, all mechanical gear train. The weakness in the design is simply it's harshness if you want to use it for "splitting" (really only an issue with manual trans, and with practise, it can be done quite smoothly), and its very small oil capacity. With only 1 quart on board, a leak could be bad. If you are over 30k and running fast, heat buildup could be an issue (is also a big deal with the GV at those weights). Stick with a full synth 75W-90 gear lube, Mobil, Redline, etc.
However, don't expect some big gain in mileage on a diesel. You MIGHT see one mpg (which is still significant), but I would be surprised if you got any more. If you were always running empty, a rear axle gear change is cheaper, but if you want to go bewtween towing and empty gearing, this is the best way by far. The other option (GV) won't work in 4x4 - a big deal if you tow in the rough or snow.
You will be amazed at how much quieter the truck can be with the revs down by 20%. Almost worth the price of admission (in my admittedly noisy 450).
And, I forgot to mention, these things are bulletproof.
2000 F450 Lariat 4x4 tractor, rebuild at 200k in '12, Air Dog, Reg Mod, HX & HP all in hard SS lines, bypass filter, Banks Power Elbow w/3.5 dp, no intake heat, CCV mod, AIS (w/extra hole), some big Alliant single shots, GP indicator LED, custom 4" exhaust, 4" USG exhaust brake, custom alum. rear diff cover extension (dipstick & temp), Detroit locker, ESPAR D5 aux. heat, custom alum tow deck and fuel tanks, Bushwacker 1 1/2" flares, 9k winch, gin poles, JWSpeaker 8900 LED headlamps in XL grille, Lightforce 240GT (still Halogen, but VERY bright), Hella Micro DE HID fogs, KW = vision plus (Isspro) instruments, more to come & lots of other diesels