Another question for you experts out there. i my vacuum pump died last week, so i replaced it and did the SD tensioner mod over the weekend. my brakes are back stiffer than ever, which is great, but the new tensioner still tick-tocks back and forth about 1/8-1/4" consistently and my crank pulley still bobs up and down ever so slightly.

background: while i was trying to determine whether it was my vacuum pump or brake booster that was suspect last week, i noticed that my crank pulley had some slight motion to it - other than its normal spinning, of course. i figured it was just my eyes playing tricks on me from the vibrating belt coming off of it to the idler/tensioner and that a new tensioner would fix it. while i had the belt off, i checked all pulleys in the system for free rotation and in/out and side/side shaft play. all were in perfect condition. then, i climbed under the truck with my back on the ground, put two hands on the crank shaft and pushed and pulled up and down as hard as i could and didn't feel even the slightest bit of movement. figured i was good to go, so put it all back together.

however, after all was re-assembled, the new tensioner is still tick-tocking, so i gave the whole system a good stare-down. No motion in any other pulleys, but noticed that the crank pulley is still bobbing up and down ever so slightly. I wouldnt describe it as a wobble, but more a bobbing up and down. the front face of the crank doesn't move at all, but if you look at the bottom of it against the ground below, it appears to move up and down by about 1/16" or less each time it goes around.

a few searches on the forum here didnt reveal much in the way of others with similar observations, but in perusing the shop manual, i came across the procedure for replacing the crankshaft damper: http://www.thedieselstop.com/faq/949...e=stjs73br.htm

its looking like this is likely my problem. does anyone disagree or have other suggestions or other syptoms to look for? then, of course, how serious a problem is this? it would seem like having the crank shaft assembly out of balance certainly isn't good for the engine/bearings, but since there is a wear item inside of there, i wouldn't imagine it to be something immediately fatal...

as usual, any/all input is greatly appreciated.

Thanks!

 

The harmonic balancer (which is what you're describing) is a two piece unit that a layer of rubber inside it to help dampen the vibration. If it is wobbling, it is likely because that rubber is worn. I think a little bit of movement is normal, but if it is out or kilter far enough to make the tensioner jump around you might want to thing about replacing it. That's my take anyway.

I don't want to sound like I am trying to make a sale here either, but if you decide you want to replace it, PM me. I have a couple laying around.

 

good to know its likely just this balancer and not a bent crank or bad main bearings.

as for the amount of movement, it is extremely slight. like, if it were any less movement it would be zero. you really have to stare at it a long time to begin to see it. as for the tensioner moving, i just attributed it to the crankshaft since every other pulley is completely motionless... is there anything else that could be causing the brand new tensioner to tick-tock?

as for timing of the harmonic balancer replacement? since the service procedure requires removing the radiator, i'd like to time this job with some other bigger work - namely painting the whole dang truck since i'll be yanking the grill and radiator to do that. think another 6 months with the balancer as-is would cause any long term harm?

...pm to be sent shortly