The Stovebolt Site Forums The Parking Lot Big Bolts Two speed vacuum Rearend 58 Viking 60

Sorry to ask such a basic question but I'd like to know what I'm doing before trying to drive my 58 Viking 60 graintruck on the open Rd for first time. I've got her running and stopping but have only driven on ranch road. I want to try her on paved county Rd. How do I operate the vacuumed two speed rear end and how can one tell which gear ratio its in when starting a drive! The lever / pull cable on the SM 420 tranny gear shift operates ok and I don't think I have any vacuum leaks as the hydrovac brakes work and engine runs smooth etc. thanks.

The shift button on the gear shift lever will have the rear in Low range when it's down and Hi when it's up. I drive all of my 2-speed trucks pretty much the same way...start off in 2nd Lo then 3rd Lo then 4th Lo and then pull the button up, let off the gas (don't touch the clutch), wait for the rear to shift and stomp back on the gas.

If I need to downshift due to a someone stopping in front of me I just leave the rear in Hi and go back down the gears as needed using the clutch to shift.

If I'm pulling a hill and need to drop a gear I downshift the rear first...I push the button down while staying on the gas, then let off the gas for a second or two for the rear to shift and then stomp back on the gas (I don't touch the clutch). If I need to drop another gear I just leave the rear i Lo and run back down as needed using the clutch.

If I top the hill in 4th Lo and start to pick my speed back up I just pull the button back up, let off the gas and stomp back on it after the rear shifts.

Any time I come to a complete stop, I start the process all over again in 2nd Lo. The only time I ever start in 1st (granny) is if I'm on a hill and loaded.

Hope this helps,

Mike B

I drive mine around empty most of the time and just leave the rear in high. The main time I use low on the rear end is to go from 3rd hi, to 4th low, then 4th high or as Mike B said, from 4th high to 4th low when pulling a hill and need a little more power.

Mike B is right on as far as how to shift the rear.

Thanks Mike. So good to know a practical guide for driving this beast lol. Does one hear the Rearend shift in and out of low nod high range with an autible sound.... Or just feel the shift in the seat of the pants??

you should be able to hear and feel it. especially if you shift it wrong, you'll hear it grind before it gets into gear!

Really, once you shift it a few times, you'll get it. (think of shifting your trans without using the clutch, same basic idea as but it shifts much faster than you would shift the trans).

When you move the shift button the rear end shift actuator actually moves and preloads the shift mechanism, but can't overcome the engine load until you let off the gas and then it slaps it into gear.

Shifting from Hi to Lo when not under load (like on a flat straight away) will cause the gears to grind. That's why I just leave it in Hi when slowly rolling up to a traffic light and wait until I'm at a dead stop to shift it back to Lo.

You'll know when it happens! Just get out on a quiet road and practice a little, it's not hard to figure out what works for you.

Mike B

If it does not shift properly, check the vacuum plumbing.

Ed

A BIG vacuum reservoir with a one-way check valve will make a huge difference in the shifting speed. I have used empty Freon canisters and occasionally a recycled Propane gas grill tank for upgrading vacuum systems on bigger trucks where there's lots of room to hang a big tank off the frame. It also improves the reserve capacity of the brake booster in case of an engine stall.
Jerry