I been doing lot's of jobs where the contractor wants to use a 3 1/2 to 4 slump..fine the pump will eat the hell out of it..problem is the grate won't allow it to pass to the hopper..I need a hopper vibrator..12 volt..anyone have a spare they would like to get rid of..needs to work and not be ungodley expensive..we used to have vibrators on all our pumps and the state said it messed with the slump..so now they are reluctant to put a laborer on the back of the pump to push the stiff stuff through then they say where is your vibrator..go figure..anyways long story short ..I need a vibrator

For a very good aftermarket vibrator, try vibco.com.

I put a DC500 on my hopper grate, I mounted it on the underside to keep it away from mixer chutes.  Use good bolts, and have a competent welder mount the plate.

yeah that's also about $700

Or mount it behind or on the side of the hopper, no chutes to worry about and easier to keep clean.

Finally,it's the contractors responibility to get his crap into your hopper.If they wish to pour some outragious stuff (low slump) they need to be ready to provide ramps of a safe and logical approach.One installs a vibrator,you'v done your part 100%

Pumpjockey is right on mount it under the grate,I got two derferent kinds Cougar brand will only last maybe a  year, I just purchased a VIBCO  DC-60  for my Olin line pump and its on the hopper about midway and the  last cougar is mounted on my grate,I think it is and DC-80, THE BAD THING ABOUT VIBRATOR'S IS THEY ARE SELF DESTRUCTIVE.

I took the one off the back of the hopper and relocated it to the grate with a couple of bolts and a flat plate of metal. A couple of braces so the mixers cant hit it and your grate will eat up the worst loads in the world. Bring it on balls and dry mud you've meet your match