? Re: Correct flexplate for C4 > AOD conversion

[SoCo66]

Greetings:

Having just completed a C4-to-AOD transmission conversion in my '66 vert, I have some follow-up issues to resolve and am seeking help from any of the "experts" in this area. So here's the history...

I procured a used AOD tranny from a 1989 5.0 Mustang and had it rebuilt at a local trans shop. In addition to the tranny, I provided the shop with a B&M Shift Improver Kit, 2400 Holeshot TC and flexplate. The flexplate recommended for this application was the B&M p/n 402322 - 164T, 28oz (see http://www.summitracing.com/parts/BMM-40232/). Upon installation and testing by the trans shop (who has done a number of these swaps), the tranny ate itself and had to be removed and essentially rebuilt again. According to them, the flexplate provided was NOT correct and was the direct reason for the initial failure. They reassembled using the "correct" flexplate (specs unknown) and called it good, noting that a starter change was also required.

From the tranny shop, the car went directly to my mechanic to finish some suspension work. Upon completion of the work and subsequent test drive, my mechanic has now mentioned that there is a significant vibration which occurs at high RPM which was not present prior to the trans swap and it is his opinion is that this is due to eng/tranny balance issue that may possibly be the result of an incorrect flexplate having been installed.

The car is going back to the trans shop today. Can anyone point me in the right direction re: direction to take the conversation with them? A couple of questions come to mind:

• What was "wrong" with the flexplate provided?
• What is different about the flexplate installed during round 2 of the trans rebuild?
• Why was the starter replaced (I've never heard anyone mention that such a replacement was necessary as part of a typical swap)?

Any other thoughts? Thanks in advance for your suggestions

[yelostang]

You have the wrong one. There is a 50 OZ imbalance to deal with ie AOD and 5.0 HD in a 65 cvt.
Had the same problem, putting a C-4 trans with the HD 5.0 Buttoned it up and headed across state to put miles on it.Drove it around town first and put about 150 Miles on it.No problem.
Drive across state to Naples, Fl. Never went over 60-65 and varied speed a bit. Np probs!
Upon return, decided to "let it out"! CHEEZ!! Hitting 80MPH the car shook uncontrollably!!
Put it in N and let is coast down, put it back in drive at 60 OK! Took it to 70 and still OK.
Finished drive back at 55 mph!
When buying that engine, person gave me a flat box with (2) flexplates. Getting back, first thing, was to check that flat box. THERE rested the CORRECT plate! Couple friends helped install and I handed them the WRONG ******* PLATE!!
Good or bad, never changed it until switching engine back to a 289. That same 5.0L is in
my 68 cvt WITH C-4 AND the correct plate

[GypsyR]

Right off, that B&M plate is for a C6 transmission. A C6 flexplate has a different offset. Which means the converter was pushed backinto the front pump and killed the pump. I've seen that happen a couple of times.
For an AOD retrofit behind a 289 or 302 I use a Pioneer FRA205 flexplate. Technically a 1991 Ford Crown Victoria 5.8 flexplate. Runs about $60 at any local parts store.
I've seen 50oz 5.0 flexplates used incorrectly on 289/302's once or twice and it made a pretty bad vibration throughout the rpm range, not just high rpm's. Still could be the wrong balance flexplate, just noting what I've personally seen.
There used to be "manual" and "automatic" Ford starters. Later models are more unified. Puzzles more than a few people when they retrofit a late model five speed manual and then need an "automatic" starter. I've run into that with automatics too when swapping stuff. The "nose" depth of the starter needs to match the offset of the flexplate teeth to engage properly. Since I know for a fact a C6 and AOD flexplate have different offsets I would imagine it also changed the gear tooth offset when they swapped and the starter you had would no longer engage properly.

[SoCo66]

Originally Posted by GypsyR

Right off, that B&M plate is for a C6 transmission. A C6 flexplate has a different offset. Which means the converter was pushed bac kinto the front pump and killed the pump. I've seen that happen a couple of times
For an AOD retrofit behind a 289 or 302 I use a Pioneer FRA205 flexplate. Technically a 1991 Ford Crown Victoria 5.8 flexplate. Runs about $60 at any local parts store.

GypsyR:

Thanks so much for the info... While the recommended Pioneer was not locally available, the '91 Crown Vic 5.8 specs led us in the right direction and we were able to source an ATP p/n 04252 for this same application. It worked like a champ with minor modification (larger than stock studs on the B&M torque converter required a bit of opening of the mounting holes in the flexplate).

pws

[GypsyR]

Glad to hear it!