I've got the 63 Chev trucck manual [which covers entire line] in front of me and it covers two aux trans-the Spicer 5831 three speed and the 6041 four speed. The best way to identify either of these seems to be by the number of PTO shafts and by the size & type of the brake mechanism on the rear.
The 3 speed has 2 PTO's, a 10 1/2" X 3" band brake, takes 4 pints of lube and has ratio's listed as:2.00:1 puller gear, 1.27:1 underdrive, and direct drive.
The things that stand out in my memory from the two weeks [out of six] that I drove a twin-stick while I was a student at the Calif Trucking Assoc Driver School in 1976 were that the correct way to drive was the exact opposite of what you would expect: you would start by putting the main box in either 1 or 2 depending on grade and load, put Aux in under-under, then under, direct, then over--the next shift up used both sticks and was to first shift the aux back to under-under and the main to 2 or 3 [as above] and do both quickly enough so that neither of the internal gear trains slowed down to the point where the mesh was no longer possible. The other thing that added to the joy of driving this setup was that the stick for Aux was far enough to the rear that it was aukward for both sholder and elbow joints--AND the last thing that made this such a joy was that the shift pattern was NOT the fimilar "H" but instead was a pattern with u-u in the left front, u in left back, direct required going back to the neutral slot then to the right and then to right-rear with the shift to over being straight forward to right front[are we having fun yet?] It was critical that when shifting either up or down between under and direct that the stick go all the way to the neutral slot, then squarely to the other side and squarely into its final position. If there was even a slight error in this shift the result was that the aux box would then be in TWO GEARS AT THE SAME TIME!! I will never forget the one time it happened to me: on the Long Beach Expressway during evening Rush Hour-having to climb out of the Tractor with a large hammer-releasing the locks and jacking the cab up-climbing up on the left rear fuel tank and reaching way over with the hammer and pounding both sets of links into their neutral positions. After that came all the same in reverse order, restarting the engine, etc.
If the 3 speed is what you have, it's 14 pages including special tools and specs, which is about the max I could scan and send over a dialup connection without risking my ISP or yours getting POed. Let me know if you need it.
