Just completed a complete frame swap and didn't know what this was when I was putting it all back together.

I'm almost sure it probably needs a vacuum line going to it.

 

I think that is the cruise control actuator, just a guess.

 

Yep, thats what it looks like to me also. Cruise control vacuum actuator.

 

I don't have a vac line going to it right now, but my cruise works good. How is it supposed to be plumbed into the vac system?

 

It may be the vacuum sensor. If I recall, that looks like the sensor on my old 1989. Do you have any warning lights on?

 

It's a sendor for the vacuum system, if you lose vacuum it turns on your brake light in the dash

scot

 

The cruise actuator is under the drivers side battery.

 

It is a vacuum sending unit. The repair manual states that there is a vacuum spec that must be maintained to operate the brake booster. If your vacuum signal gets to low, you will get an idiot light on for the brakes.

Ronnie

 

isnt this sensor alittle redundent, we have hydraboosters. i looked at my truck i dont have it. but it looks like the adjustable shock you find on like a mitsu. 3000GT or stuff like that. thats my .02$ or well .10 with inflation

 

You must have a 97 or later truck. 96 & early had vacuum assist brakes

 

That is the vacuum sensor for the vacuum-boosted brake system - triggers the Brake and ABS (if you have it) failure indicators in the instrument cluster.

Low vacuum in your vacuum-boosted truck is very dangerous, as you lose braking - later hydro-boost trucks just lose ac\heater and cruise functions - if that was never connected from when you got the truck, your alarm indicator bulb(s) are probably removed

As a life-saving suggestion, I'd re-connect it and get it working, as those vacuum pumps are known to fail suddenly

Or, get the hydro-boost from a late '97 or 12v '98 WITHOUT the 4w ABS - ALL the brake-line fittings are metric on the 4w ABS systems, won't even interchange with the orig pre-'97 stuff

Dumping that vacuum-booster was the first absolutely required modification to my '96 3500 - passenger cars get away with it because gassers (patooie!) have an eternal source of vacuum

Our eternal(?!?) source of vacuum is carbon\graphite vanes sliding in\out of slots at high speed around an aluminum chamber, no lubricant

I'll take my chances with the power steering pump - which, btw, you'll need the reservoir from the hydro-boost version for the additional return-hose fitting