Re: Dual High

Posted by Dan on August 14, 1998 at 10:25:09

In Reply to: Dual High
posted by Joe on August 11, 1998 at 07:58:44

: : On one of the AA chassis I have, there is a dual pedal that comes up thru the floor. I'm trying to remember its location. I think it was to the left and back from the clutch pedal. Did some AA have "low range" or what were they for?Ken
: Ken
: Sounds like you have the "Dual High" unit I mentioned earlier. On certain of the "heavy duty intended use" AA chassis' Ford installed a two ratio planetary gear type speed reduction unit which would result in 8 forward speeds and 2 reverse when combined with the standard AA 4 speed transmission.(Warford was considerably more than this)A power take off connection was frequently part of this arrangement.
: This unit was installed between the rear universal joint on the transmission and the second frame crossmember where there was a second universal joint.
: If not "dual high" equipped, this space was filled with an enclosed shaft that served as a direct connection.
: Victor Page in his book "Model A Ford - Construction, Operation and Repair" ($21 at any major parts supplier) describes the "dual high" as applied to the 1928-29 trucks in modest detail.This book has the only cutout picture I've seen showing the internal workings of the dual high.
: Another modest description of the dual high is in "AA Truck - Supplement to Restorer's Model A Shop Manual" by Jim Schild ($12.95).I recommend this book if you're restoring your AA.
: The "Ford Service Bulletins" ($17) describes the dual high in fits and snatches but nowhere (if memory serves me) is it covered in any wealth of detail.A lot of information on the brakes and wheels and transmission but not much on dual high.
: The "Parts Price List" ($11) has about half the book devoted to the AA version of the Model A and includes about a page on the dual high unit.From my book it is apparent that at least 3 different dual high variations were made with Housing numbers AA-4830-AR and AA-4830-BR and AA-4830-CR.These likely differed only in details of the casting or machine work, or the inclusion of a power take off mounting flange.
: I have not seen in the literature evidence that any of these included any sort of overdrive arrangement.I suspect that the dual high should have properly been named the "dual low" since the literature indicates that they were used primarily for a reduction in speed and increase in load carrying capability.
: Hope this all helps.Best regards,
: Joe
Are you looking for one of these trannies? I remember my grandfather pointing out a '30 AA chassis at his place and commenting about its rare auxilary tranny etc. in its drive train or something to that effect ( this was in the '60's ). My brother has the chassis now, in the Toronto region. E mail me for his phone number if you would like.
Good luck
Dan