Dual transmissions?

[snooziums]

I was wondering if anyone actually thought about installing dual transmissions, or if anyone actually did that?

I have been having wild thoughts about mating another transmission to the back of the one I have, since the back of what I have used to go into a transfer case.

[heep70]

NO, but they is such thing as T-Case doubling to get a lower range for rock crawling.

The was or maybe still is a Dana 21 T-case on ebay.

[72hiboy4x4]

old school big rigs use a browning transmission hooked behind the main tranny. either 2 or 4 speeds were available

[snooziums]

Okay, so that leads me to another question. The transmission I have bolts up to a Bronco transfer case (I have no clue as to what year). Do the 4wd F-series use the same transfer case? I have heard that the Hyboys may not work, however I thought that all 4wd F-series were Hyboys, until I was told my another member that there were some with "D.T.C" (thanks for some of the help, wapackrat.

So how many setups were there, and which ones will work? I showed pictures of the back end of my transmission on an other post, and I know that it bolts to the bell-housing I have, and I am not sure what else will bolt up to that bell-housing.

So much confusion.

[heep70]

All F250 (Highboys) have NP435/T18 & devorced T-cases. All F100s were married (I believe). As far as I know they used Dana 21 single speeds and 205 dual range t-cases.

As far as what exactly bolts up to yours I am not real positive. What t-case was on it?

[hardtailjohn]

As far as the "old school" big trucks go, they used 2, 3, and 4 speed aux transmissions, and most of the mains back then were 4 or 5 speed with some 6 speeds out there. Some were "married" cases (usually Mack) and some were not. The big thing there was that the main box was a wide ratio, and the aux is a close ratio, so you could "split" the gears in the main. The first "B" model Mack I ever drove had a triplex (5 speed main, 3 speed aux) and a 2 speed box behind that, so there was a bit of overkill there for sure.
I've seen small trucks and even pickups with aux transmissions in them, and Brownlipe and Spicer used to make some pretty nice 3 speed smaller transmissions.. some had an overdrive and some were 3rd direct... but they're tough to find and expensive when you do!
Just my
John H.

[Rockcrusher]

Dual transmissions have been done . . . Both Auto+manual and manual+manual. The major consideration is selecting a rear gearbox that will handle the multiplied torque from the front box. The second consideration would be mating the output and input shafts of the 2 boxes.

There was a thread on Pirate 4X4 about married GM SM465's (complete with pictures). Do a search in the General 4X4 section.

I also vaguely remember seeing a writeup on married Ford 3.03 3 speeds. If memory serves me correctly it was done by a guy from up in Canadia

[hardtailjohn]

Here's a great little video from our own "freightrain" aka Larry (member here!) driving his B model Mack, working 2 sticks... he does a good job! Worth a look.
John H.

http://fords.kilonet.org/freightrain/bmodel.wmv

[72hiboy4x4]

heep70, thanks for the real info. I knew it was something like that but couldnt find the info I was looking for at the time. as always a little teamwork gets the right info out there!