Two-speed Rear Axle Questions

[Guest philedmonds]

My fire truck (F1BA) has a two-speed rear axle and this is the first I've encountered. It appears that the button on the gearshift lever actuates a vacuum valve on the firewall that actually shifts the rear axle from high to low ratio. I do not yet know if the rear axle shifter works and I have no clue about the vacuum valve. I don't have the means to test it. The valve also has a small vacuum line to the speedometer. I assume it "shifts" a speedometer gear so the speedo reads correctly regardless of whether the rear end is in high or low ratio. I assume the valve (Eaton) has some soft parts in it and I'd like to get it rebuilt on general principles. Am I correct about my speculations on shifting the rear end and on the speedo? Does anyone know where I can get the vacuum valve rebuilt? Also, the rubber mount for the valve is shot - are there any sources for this part or do I need to make something? Thanks so much. Phil

[Steven Hood]

Try Vintage Power Wagons in Fairfield, Iowa.

www.vintagepowerwagons.com

[daimlerchryslerman]

Hi There,

I have a 1950 Fargo 2 Ton with a 2 speed diff.I could tell you how to shift it if you want.Although it Does not shift toO well in this cold weather til the diff warms up a bit.They suggest leaving it in low range when not in use.I finally figured out why in this cold weather.

I was in gear with the engine running and the clutch out and going no where.

I looked at my drive shaft and it was moving.I guess it can get stuck half way between gears if diff oil is too cold and thick.You are right about the speedo.I had to put a one way vaccum valve in the line so the speedo works in high range cuz the speedo would go up and down when the vaccum cut in and out like your wipers do when engine vaccum changes !

Ray Morris

[MBF]

Yup-I remember an old mechanic telling me that you had to shift those old vacuum 2 sppeds like you were born on them. Ok when its warm, but when its cold they're a whole other animal. I've got a '39 Dodge dumptruck that has a mechanical (lever operated 2 speed) behind a working 5 speed. That was one you could feel you way through whenever you were driving it. I actually kinda liked it better than the electrics since you could control it better. Mike