OK, with a 39" tire I came out with these approximate speeds and RPM's:
Gear RPM Lo Hi
1st @ 4000 8 11
2nd @ 4000 16 21
3rd @ 4000 33 44
4th @ 4000 57 76, or 66 @ 3500
Definately a split shift required when running it's max load capacity and a weaker motor, but thats with an older motor, the one you have is runing at least twice the ponies. With a more modern 350 you should be able to pull a respectable load up through 4 lo then shift it over and ease up to speed.
As for shifting the rear, I have the instructions that were on my visor (just fabricated a new visor and instruction sheet).
Dunno if it will help, I'm still figguring out my truck, but again it's pretty sloppy back there.
TWO SPEED AXLE SHIFT
To shift axle only:
Into Low-
With accelerator down, move lever to low. Ease up accelerator, then press down, at the same time quickly disengage and engage clutch.
Into High-
With accelerator down, move lever to high, remove foot from accelerator, disengage clutch-pause-engage clutch and press down on accelerator.
To shift transmission and axle:
Into high gear and low range-
Ease up on accelerator, shift transmission, using double clutch method, and just before engaging clutch, move lever to low and press down on accelerator.
Into low gear and high range-
With accelerator down, move lever to high, then shift transmission, using double clutch method. Axle shift will take place while transmission is shifted.
1. Always keep accelerator down when shift lever is moved, except when shifting into higher gear and low range.
2. Always park in low range and start in low range (this was printed large and bold).
3. See instructions in owners manual.
Might help, or might confuse the heck out of ya, whatever works!
