Vacuum shift is used on some models to switch between 2wd and 4wd. Lets you shift with a push button on the dash instead of shft linkage. Can't imagine why anyone would want one though (more things to break down).
when you have a vacuum shift and three speed on the tree, theres nothing cluttering up your floor
dont think theres any advantages to it other than that and that its kind of fun to have some old technology around- I didnt realize there was a column shift with clutch till i test drove my 40
I've have it on my 70' FJ-40 and I've never had a problem. I was going to replace it with the new twin shift when I did my V8/NV4500 conversion, but I was talked out of it. The mechanical has a tendency to bind when the body and the frame twist (normal). Vacuum lines can twist and still work. The twin shift is designed to twist and not bind, hence the two shifters. Food for thought. '
I have heard that it is easier to shift into 4WD "on the fly" with the vacuum. Don't have anything else, so I cannot really compare. I also like having the floor clear in front. Bench seats, driver and 2 passengers in front, which is why they went to 3 on the tree to begin with. Works for our 3 person family. Dogboy in back .
The only problem I've had with the vacuum shift is that (I suppose during its sojourn at the bottom of a pond) the vacuum chamber was filled with water. It still worked, until the temps dropped below freezing for a while . Emptied out the water, once I figured it out. Works fine in all weather.