Originally Posted by klhansen
I believe they were mostly used on big bolts with vacuum operated 2-speed axles. But, yes, they can be used on pickups or cars. I found one on a 235 that was going to go in a 1937 pickup. There happened to be a spare in the seat of the "project" truck. Should have snagged that one as well.
My '57 Big Bolt has HydroVac brakes and I added a 2 speed differential, the vacuum from the engine alone is sufficient to operate both of those components. My truck came standard with electric wipers so I can't comment on that function. I added a vacuum reserve tank when I incorporated the 2 speed but I think it would have worked ok regardless. The one difference with my truck vs. an earlier model is that it has the 283 V8 and may produce vacuum better than the inline 6.

Last edited by 78buckshot; 10/11/2026 11:19 PM.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy