Ok I know you arent supposed to use a 6.9 flexplate with a 7.3 and visca versa. Well the 7.3 I am swapping in had a manual behind it and I cant find a flexplate for this thing. The parts store I work at lists a flexplate for every motor except the diesel which it only lists a flexplate ring gear for. So what is the difference with these things??
Flexplates
- Thread starter Hyde
- Start date
towcat
Full Access Member
you match the flexplate/flywheel to your motor according to the trans. whatever trans you have, the flexplate coming off your old motor is the one you use on your "new" motor.
hope this helps
towcat
Full Access Member
It really boils down to what you're comfortable with doing. There's many people who say it's ok and many who say don't do it. I don't have a problem mix/matching engine/trans combos.
towcat
Full Access Member
hyde-
here's the issues. due to the fact that there are specific part numbers for harmonic balancers for the 6.9/7.3 to hook up with specific transmissions, there are some who are nervous on doing a mix-n-match. truth is, these motors are internally balanced design, so they are designed to run whatever you hang off the back of the crank. these motors are not only found in fords but also IH S-series with a dizzying choice of transmissions. Adding to this, wrecking yards will sell you a motor without much regard to what's on the backside and there's really no serious complaints with doing so. If there was, you'd be seeing it here. If I were you I'd install and run with it. If you do have a vibration that troubles you, swap the harmonic balancer.
good luck.
here's the issues. due to the fact that there are specific part numbers for harmonic balancers for the 6.9/7.3 to hook up with specific transmissions, there are some who are nervous on doing a mix-n-match. truth is, these motors are internally balanced design, so they are designed to run whatever you hang off the back of the crank. these motors are not only found in fords but also IH S-series with a dizzying choice of transmissions. Adding to this, wrecking yards will sell you a motor without much regard to what's on the backside and there's really no serious complaints with doing so. If there was, you'd be seeing it here. If I were you I'd install and run with it. If you do have a vibration that troubles you, swap the harmonic balancer.
good luck.
riotwarrior
Full Access Member
Any more input on this? If I find out for sure I can put this motor in tonight and that would make me happy
Engine differences between the 6.9 n 7.3 in balance could potentially cause a potential failure. The flex plate for the 7.3 would have been balanced for a 7.3 and the 6.9 the same...for the 6.9.
The bore size being different and the stroke the same means that the reciprocating mass would be different. That affects the balance but not as much as say different rods or crank would affect the rotating mass and balance.
It may work trouble free as I have done this with gassers for years with no major catastrophic failures. Seeing as these engines do not spin up like a gasser, I suspect it would work with minimal issues, though not having inspected and investigate the differences between the two parts in mention I cannot say for certain it would be ok.
Double-S-Diesel
parts seller
ive run 2 difeerent truck with a 6.9 4 spped flywheel behing 7.3s, one was an out motor and the other a 5 speed.
now when it comes to flexplates for autos the c-6 is different than a e4od
now when it comes to flexplates for autos the c-6 is different than a e4od
Mr_Roboto
Full Access Member
This topic has been beaten like the proverbial dead horse and has never been settled. But enough people have swapped parts and the trucks have not imploded.
It all comes down to whether the engines are internal or external balance, and if externally balanced if the two engines are balanced different at the flywheels.
Towcat says they are internal balance and I have no reason to doubt him.
It all comes down to whether the engines are internal or external balance, and if externally balanced if the two engines are balanced different at the flywheels.
Towcat says they are internal balance and I have no reason to doubt him.
Jake S.
clueless...
I am running a flywheel from a 7.3 on a 6.9 so I can run a zf5. Runs great no vibrations or problems after 10k miles
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Well we bolted it all together last night. Anyone know the torque specs on the flexplate bolts? 55 lbs seemed like I was gonna twist the heads off which has happened before (oops not fun) so thats where they are. Should have it ready to go by next week, I dont have much time to work on it so it goes slowly.
icanfixall
Official GMM hand model
The torque for the flywheel bolts is 47 lbs..... Use some sealant on the bolt threads because they enter the crank case oily side. This is directly out of my Navistar servive manual.
