The Stovebolt Site Forums The Parking Lot Big Bolts 2 Speed Rear 1946 2 Ton

If there is no vacuum sent to the read end will the rear stay in the high speed gear of 6.02 or go into low speed gear of 7.98?
Thanks. Jeffrey

As far as I know, it should stay in whatever it was in last.

I have to get under the truck. If there is 1 diaphragm with a spring.

I figure vacuum applied moves engages say low, when vacuum is cut off the spring then moves the diaphragm in the other direction and it will stay in high forever until the spring fails.

But I'd rather know then guess.
Jeffrey

When I first got my 46 2 ton going I split the pancake at the diff.and shifted the diff.with a vise grip a few times to loosen it up. Then hooked up 3/8 vacuum lines to the factory switch on the dash. After feeding wd-40 into the switch (with the vacuum pulling it in)it stopped leaking. I use it all the time to down shift for going around corners. The diff. will stay in what ever gear you leave it in,there's no spring pressure or anything ether way. But if you leave it in low you'll go really slow!

We bought the truck and the rear was in high. And we never tried to see if it would go into low.

Have not needed to put the rear into low.

Though what I wanted to know and you still have me confused: is if I disconnect the vacuum to the rear will the rear stay in high hear?

To me all that steel lines/tubing and several pieces of vacuum hose appears to create too much opportunity for a vacuum leak.

So I can eliminate a vacuum leak before one happens. I am probably over thinking this. Though I would like to know how the vacuum rear works.

I know how vacuum wipers work, how fuel pumps and power brake boosters work. Jeffrey

Yes: The diff will stay in what ever range you leave it in with no vacuum. You Don't need vacuum to hold the diff. in ether high or low range. Mine was in high when I got it. After several years of driving it, I got 3/8s steel brake line and vacuum hose and hooked it up to shift on the go. Also got the vacuum switch to work and not leak by letting it pull in W-D 40 with the vacuum.There's a really cool reproduction sticker for the dash that shows the switch and shows how and when to shift. Mongo's Garage on this site sold me mine for $10. Google Mongo's Garage to see sticker.

Thanks for straightening me out. Jeffrey