I have built a bunch of Dune buggies. With VW engines, when you make a mid
engine configuration, the ring gear needs to be flipped over inside the
case. I usually included a "beef-a-diff" carrier when I did this, along
with a 1-1 top gear to replace the .890 -1 top gear, along with 1st and
second gears that made it a close ratio gear set. Then, when you built the
air cooled engine up to about 175-200 hp, you had enough beans to make the
thing fly.
If the VW engine was replaced with a Corvair engine, the ring gear
swap was required, as the Corvair turns the opposite direction from the VW.
The VW transaxle is none too strong with tall final drive gears or huge
paddle tires that load the transaxle up. They will live with up to 200 hp,
but not much more than that. But, the sand usually destroys the engine
before the transaxle gives up the ghost. You want to go fast, you have to
pay the cost. Speed costs money, how fast can you afford to go?
Jim Hupy
Salem, Oregon
On Fri, Dec 25, 2020, 7:09 PM Richard H Staples via Gmclist <
> Johnny,
> The THM425 IS a "regular" transmission, ie a THM400, as used in millions
> of larger GM vehicles from mid '60s to the '80s. The only significant
> difference is the chain drive, and the 2 overrunning clutches which are
> installed "backward" when the tranny is assembled. Yes it turns
> "backwards",
> but so would any transmission driven by a chain off a normal
> clockwise-rotating engine. (Extra credit: What are the two cars whose
> engines turned
> counter-clockwise? Hint, they both begin, or began, with a "C" and I
> owned one of each.
)
>
> Flipping the ring gear is done in a VW when you install one of those
> engines. In a GMC, it would only be necessary if you installed a
> conventional
> engine mounted backward back near the dinette.
>
> HTH
> Merry Christmas and Happy Solstice to all!
> Rick Staples
> --
> Rick Staples, '75 Eleganza, Johnstown, CO
>
> "Advice is a dangerous gift, even from the Wise to the Wise, and all paths
> may run ill." -Tolkien
>
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