by Fred S » Tue Dec 17, 2013 4:14 pm
Reasoning is purely what gear you need for the intended purpose. Manual control is typically only really needed on grades at very slow speeds, and typically with a heavy load behind it. Putting it in L does engage the Reverse band, thus taking the stress off of the sprag, or one way clutch as its also referred to. I've yet to see anyone break a sprag from launching with a load or at a track. Where they break is when you float from reverse to drive or drive to reverse without the vehicle stopped.
So back to the original question asked. upgrading to a 47 case, gets you the provision for the double wrap L&R band. That's the benefit. Compare the bands, and you'll see the major difference. Steel front 5pinion planetary can be done to either a 47RH or 518, as all 47REs for diesels already have it. If you can find a core 47RE front half for real cheep, which has the major internal hard parts, I'd go for it, as Goerend is saying they do.
Warranting broken 518s would get old real quick, as people tend to overdue it on load or power.
So decide what you will use it for, and decide if a 518 upgrade is enough for you're need.
92 W250 LB Crewcab 3" Alcans, NV5600 4x4, 35inch Toyo ATs, some tweaks
2001 Golf TDI TDTuning-Stg4, R520s, SBC, 17/22
94 Toyota Ex-Cab 4x4 (01 ALH(TDI)) TDTuning-Stg4, PP764s, SBC, 17/22