Which Flywheel Torque Spec Is It

[IBMobile]

When looking up the tightening specification for installing the bolts that hold the flywheel or drive plate to the crankshaft I found two different values.  In the engine section under "Crankshaft Oil Seal - Rear"  the tightening torque given is 101 ft. lbs.  In the "Automatic Transmission 47RE- Torque Specifications" chart the number given is 55 ft. lbs.  One of these is a mistake; which one is right? 

[Evan]

I think 55. Bolts are to small to go to 100

 

 

**** I think I'm wrong. Arp says 120 for they're flex plate bolts.

 

So maybe 100 is right for stock bolts

 

https://www.xtremediesel.com/arp-147-2901-flex-plate-bolt-kit

 

Edited September 13, 2019 by Evan

[Mopar1973Man]

Like on my manual (clutch install) its 102 foot/pounds for the flywheel. 

 

@Dynamic would know exactly what is a good number. 

[Haggar]

IBM,

 

I agree I found both of the different references you found....

 

I think the bolts are M12.   Need to know the class of bolt.  (and materials to be fastened)  Metric 12.9 (similar to our grade 8) maximum suggested tightening torque is 123 ft*lb.   grade 10.9 is suggested max 106 ft*lb.    grade 9.8 is suggested max 83 ft*lb.

 

This chart from the manual says the m12 at 12.9 can go to 95 ft*lb in cast iron.  Our crank is forged steel.  (significantly stronger in tension)  so I think the 101 ft*lb is fine if the fastener is 12.9 or stronger. 

 

HTH
 

Hag

[Dynamic]

Flexplate to crank: 105 lb/ft

[Mopar1973Man]

Well not far off from my 102 foot pounds that my flywheel was torqued too.. Thank @Dynamic !!

[IBMobile]

The "Automatic Transmission 47RE" chart also gives a tightening torque for the "bolt, torque convertor"  of 35 ft. lbs..   If the tightening torque is 105  ft. lbs. for eight bolts holding the flex plate to the crankshaft then you would think the 35 ft. lbs. of torque on the six bolts holding the flex plate to the convertor is to low.

[Evan]

I red lock tightened mine too after cleaning bolts and threads in crack

 

Are you using a billet flexplate ?

Edited September 14, 2019 by JAG1

[Mopar1973Man]

19 hours ago, IBMobile said:

you would think the 35 ft. lbs. of torque on the six bolts holding the flex plate to the convertor is to low.

 

Kind of like the 44 foot pounds holding a dual disc pressure plate... 

[Dynamic]

21 hours ago, IBMobile said:

The "Automatic Transmission 47RE" chart also gives a tightening torque for the "bolt, torque convertor"  of 35 ft. lbs..   If the tightening torque is 105  ft. lbs. for eight bolts holding the flex plate to the crankshaft then you would think the 35 ft. lbs. of torque on the six bolts holding the flex plate to the convertor is to low.

The converter to flex plate bolts torque to 38 lb/ft.

[JAG1]

11 hours ago, Evan said:

I red lock tightened mine too after cleaning bolts and threads in crack

 

 

[dripley]

33 minutes ago, JAG1 said:

Almost sounds illegal.

[JAG1]

1 hour ago, dripley said:

Almost sounds illegal.

No, I think he was on the phone when posting and they were giving the final report on a magniflux  for his Ford engine 

[IBMobile]

On 9/13/2019 at 9:09 PM, Evan said:

Are you using a billet flexplate ?

@Dynamicincludes an HD SFI 29.1 rated flex plate with the " Stage 2" Transmission  build package.

[Evan]

I think he recomends the billet. 

 

The other sfi stuffs goood to I think its designed to be a fuse

 

I was curious about the sfi 29 so I looked it up.

 

It basically means it passed an hour spin at 12500-13500 rpm without failure.

 

I do not know if the billet plates have been tested.

 

More research needed very interesting 

Edited September 16, 2019 by Evan

[Dynamic]

The SFI 29.1 flex plate is included with the Stage 2 build. Stage 3 and higher include a full billet flex plate. 

 

No builder would intentionally put a "fuse" in the system. The flex plate is no exception. The SFI 29.1 flex plate is more than most people will ever dream of needing.

[Evan]

Just something I read you know how stuff is that you read on this damn interweb