flywheel

[7.3L F-250]

i wasnt there when this happend but

we have a 1978 peterbilt 359 dumptruck with a big cam 400 (engines not origional)

and while on the job today we went to start it and nothing happend so i guess my grandfather looked at it and the teeth on the flywheel were missing...what can happen to cause this

thanks in advance - tj

[chopper013]

well its caused from when the appendix (belive thats the right word) kicks out from the starter it doesnt catch the starter right and can grind teeth or it can be caused from a locked up engine and in the process since it doesnt spin the starter grinds the teeth off. and one more thing that can cause this is hitting the starter while its already running which for me as a mechanic in the military thats the most common.

[diablo53]

*bendix

[chopper013]

thats it lol brain fart. been in iraq to long already

[LMJD]

...what can happen to cause this

It's not all that unusual over a long period of time. It has nothing to do with faulty starter or bendix operation. Engines generally stop at the same crankshaft position on shutdown so a certain small number of flywheel teeth get all the wear and tear. It's been a long time since I've done surgery on one of those (retirement's great), but if I remember right, they're like all the rest. After you pull the flywheel, you make a notch between two ring gear teeth with a chisel to expand it and then it will slip right off the flywheel. Then the new ring gear has to be heated with a torch to expand it, then you pick it up real quick-like with a couple pairs of pliers and drop it onto the flywheel. You DON'T want to overheat it or you'll soften the steel. It's fairly common to have to replace the flywheel ring gear on any big Cummins, Detroit, etc, during an out of frame engine overhaul.

[7.3L F-250]

ok i heard compleatly wrong...eather due to bad cell service or me just being hard hearing

what acually happend was that the flywheel broke all 6 bolts again...and they went threw wrecked the flywheel and the clutch the only thing we can come up with for this is that eather the harmonic balancer,crankshaft, or flywheel was out of balance because this is the second time in 2 years

any ideas?

[LMJD]

Personally I've never heard of that being a chronic problem with any of the 855 cu.in. series through the years, maybe someone else has. The typical double disc pull clutch/flywheel assemblies are about all the same and trouble-free too. Unless he finds something obvious like overtorqued grade 5 (instead of grade 8) bolts, or whatever, that might be a tough one to figure out. Any outside drivers that might be putting it under a shock load at times? However in heavy trucks the weakest link is purposely designed to be the driveshaft because it does the least damage and is cheapest to fix. Under a severe enough shock load it will twist itself into a pretzel and break rather than something more spendy.

[379Longhood]

If the flywheel bolts sheared twice I would look at the harmonic balancer (I know this is not the corect term) they can cause the strangest failures beyond that check for wear on the crank stub and the inside of the flywheel what about dowel pins? The bolts carry rotational shear but they shouldn't have to align the flywheel
Hope this helps
Jim

[7.3L F-250]

theres no dowel's but we did switch the dampener hopeing it will help