Hello there, I'm new to this whole forum thingy so please bear with me.
My brother recently completed a sandrail utilizing an Olds toronado 455 and transaxle.
I understand that there were a number of different front drive motorhomes made with this combo using I believe a 5.13, or something like that, ring and pinion.
With the paddle tires being quite a bit larger than on the car, the stock gearing is way to tall.
How much more difficult is it to change the gearing in the transaxle compared to a normal rearend?

http://www.geocities.com/rkusiek/Sandrail.html

 

As you probably know, the diff housing unbolts from the rest of the transaxle, making it easy to work on. You do need a case spreader to get the carrier out. These show up on ebay every so often. I'm not aware of gear sets any steeper than mid-3s. Certainly there were no such factory gear sets, even in the motorhomes. There IS quite a following of the GMC Toro-based motorhomes, so there may be aftermarket gears available. I seriously doubt, however, that a motorhome with a 455 Olds would be able to use a 5.13 gear set. Depending on tire size, you'd really be winding that big block on the freeway.

 

You might look at putting a planetary gear reduction hub out at the wheel. With that much weight in the back, you might need more tire height and footprint anyway to keep from getting stuck in the really loose sand...and this should give you the extra room to fit in planetary hubs. Just an idea.