flexplate differences between "C" and "J" motor

[smganger]

I am swapping a TH400 for a TH700-R4 (Bowtie Overdrives). I have done this swap previously with OK results (rebuilt 2x's locally to stock spec's) but very good benifits (21 MPG @ 75-80 MPH). Is there a difference in the flexplate of the "C" motor (1/2 ton) and the "J" motor in the 3/4 ton chassis? I have a 'plate said to be for "C" motor with correct TC bolt pattern and weight attached (just like the TH400 'plate in there now) and a 'plate for the "J" motor with incorrect TC bolt pattern (TH400 maybe). I think I have a 'plate that will work but I am not sure. What are the differences , if any??

[Robyn]

Any flex plate for the 6.2/6.5 will fit the engine and work fine in that respect (These engines are externally ballanced)

The Bolt pattern for the torque converter is the same for the TH400 and the 4L80 The 700R4 uses a slightly smaller bolt pattern where the plate fastens to the converter.

If the plate you have has holes that will align with the converter your using, your set.

The only difference is the bolt circle, so use the one that fits your tranny.


Robyn

[smganger]

Thanks for the info. After posting, I took a look at the 400 flexplate and decided that both plates had weights in the same place and that I could use one of the plate I had for the 700. There seems to be a lot conflicting information regarding interchangability of parts, even at the dealership level.