• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Want to break your crankshaft? I almost did today...

Will L.

Will L.

Well-Known Member
Messages
20,002
Reaction score
39,565
Location
Boulder City Nv
So... My hummer got a new Optimizer in December of 2004. Less than 100,000 miles on it. The harmonic balancer came apart, I just saw it this morning sliding under to take a measurement of something else for a member on the hummer forum. My "check HB everytime your under" policy just paid off again.

For those that don't know, I ran fleets of 6.5 trucks for years, worked on thousands of 6.5s. SO MANY broken crankshafts taught me the balancers go bad, and the crankshaft breaks. Just a weak point on 6.5s.

I NEVER run a harmonic balancer on a 6.5 over 100,000 miles as a safety margin from experience. I also learned there are only 2 options to buy. AC Delco or fluid damper. NEVER buy the cheaper ones, many times they won't last 30,000 miles. The AC Delco is good (usually) for 100,000 miles. The fluid damper is a forever part, but $$.

Never use the mounting bolt to reinstall your new one. Rent or buy the tool. Many parts houses have a free rental program.

Go check yours today. Grab the outside ring with your hand and try as hard as you can to dislodge it from the center body. If you can, it was about to come off anyways. Examine the rubber ring attaching the 2 pieces for cracking or missing chunks. Replace if at all questionable. There is a reason Scat cranks started making 6.5 crankshafts- not because the gm ones sucked- they are ok. But so many broken shafts from bad balancers. It's not like there are 1,000 people out there building hot rod 6.5s- so where do you think they get the volume of sells.
 
When I rebuilt my 6.2 , had to add a lot of heavy metal to balance the crank . Got me to thinking if the balance was way off from the start and if this could lead to crank problems . I could of used a FD but went with a new GM instead . If the outer ring on the HB is loose or gone , is this because the rubber is gone or the balancer is actually doing it's job and just done ?
 
Rubber only has so many miles in it reduced by time and heat. Heat reduces the lifetime available from the rubber. Heat is from outside temperatures, heat under the hood, and from working the balancer itself. So High heat from the AC running is one angle. High load and vibration that is working the balancer hard also can heat it up.

Age... Want to see a tire explode at speed? Run a unused spare tire that been out here for 10 years. The amount of rubber on the roads in the summer from failing and or overloaded and or overspeed tires is impressive.

Regardless the rubber starts to crack, work chunks out and ultimately quits damping the narrow range of vibration it was supposed to stop. Like a paperclip being bent back and forth it's just a matter of time before the weak crankshaft fatigue breaks with a INOP damper. GM crankshafts did indeed SUCK because the beancounters decided to cut corners on a GM diesel, yet again, and gave us a cast crank rather than the forged crank. (Like Scat now sells.) The cast crank depends on the damper working and nowhere is a mileage recommendation to inspect it from GM. Regardless with the prone to cracking everyfingthing and weak starter mount I suggest I am merely griping about a "throwaway engine design". Other owners manuals *cough* *cough* Dodge Cummins *cough* learned from GM and put a mileage inspection of the damper in at 30K.

To be clear working hard from the carnage thread crowned king: A good AC Delco damper on the front of the engine and I have not broken a crankshaft. I did replace a suspect cracking damper with 50K hard (extreme) miles on it at 2 years old. Engine was out at the time anyway.

@Will L. "The fluid damper is a forever part" No, it's limited to 500,000 miles like all similar technology dampers are recommended to be replaced at. This is around 2 or more lifetimes of the 6.5 engines so the number of people that matters too is small... But, the odometers of some of the membership here like @6.5L appear to be close to 1/2 million miles. Regardless you may be able to claim warranty at 1/2 million miles. Note: any dents to the FD housing ruin it instantly.

Reference:
http://www.overdriveonline.com/caring-properly-for-engine-dampers/
 
Last edited:
Thanks for the correction on FD lifespan.

I am of the opinion all the broken 6.5 cranks are from the balancers or main webs giving out. All the broken cranks we saw in the fleets, not one ever had a good balancer or no cracked mains.

I have seen several big blocks (gm, & ford) crack the webs like the 6.5 does, and they all lost balancers.

The optimizer crank, rods, pistons were all upgraded- but still suffers the HB failure and do not have any better balance specs. Infact, as we are discussing on the humme site- GEP balancers on optimizers dont seem to last quite as long as the AC Delco ones. We are not sure if GEP is making their own or buying AC Delcos.

Mine will only get AC Delco if I sell it or can't come up with cash for FD due to too many other new parts going in. I feel I would be ripping someone off if I sold it with known inferior parts.
 
ak diesel driver said:
3rd option powerbond
Click to expand...
Yep, I'm getting ready to put one in my duramax. My stock still actually looks good, but I want to change it anyways. Too many have broken cranks in the duramax with fluidampr's because of the added weight, ati's and the like are $$$, so I'm planning on a dayco powerbond. It's still an eladtomeric unit, but it's built HEAVY DUTY, and by design can't come apart if the elastomer fails.
 
Rock Auto has a Dayco race balancer for the 6.2 for $291 .
 
Is there anyone who has any descent amount of time running one?
I remember seeing "good deals" on other harmonic balancers like the doorman.
 
you ought to go to powerbonds website, if even 1/2 of what they claim is real it's a much better balancer than most. I've got about 6 months on mine
 
@Will L. "The fluid damper is a forever part" No, it's limited to 500,000 miles like all similar technology dampers are recommended to be replaced at. This is around 2 or more lifetimes of the 6.5 engines so the number of people that matters too is small... But, the odometers of some of the membership here like @6.5L appear to be close to 1/2 million miles. Regardless you may be able to claim warranty at 1/2 million miles. Note: any dents to the FD housing ruin it instantly.

Reference:
http://www.overdriveonline.com/caring-properly-for-engine-dampers/[/QUOTE]

500,000 miles is about 5/8 of a lifetime in my experience
 
China is Okay, as long as it's made to the Mfg's specs. a lot of times, they skimp, to make a dollar, or what they're payed. maybe a good name in the supervisors eye? free room for that week? they're payed peanuts. glad i can make 10.00 an hour guilt free.
 
deejaaa said:
China is Okay, as long as it's made to the Mfg's specs. a lot of times, they skimp, to make a dollar, or what they're payed. maybe a good name in the supervisors eye? free room for that week? they're payed peanuts. glad i can make 10.00 an hour guilt free.
Click to expand...
And $10/hr is still a Poverty Wage in America.
 
You must log in or register to reply here.
Back
Top