AOD installation problem?

[jshcobra]

Here's what I've got: I just installed an AOD on my 68 using a 28oz, 164 tooth SCAT sfi flywheel from Jegs. When bolting the transmission to the engine, as soon as the bellhousing bolts were tightened, I couldn't turn the engine. I removed the tranny and double-checked the torque converter for proper engagement and reinstalled. Same thing. If I cracked the bolts just slightly loose, the binding was gone. Comparing the new SCAT flexplate to the old c4 unit revealed that the new plate was just slightly thicker metal. Could this account for the binding?

My solution was to use two block plates, which set the tranny back from the engine about 1/32". It spins freely now, but I just read on another site that if the torque converter isn't engaged fully, I can ruin the front pump on fireup.

Now to my specific question-- if the torque converter wasn't fully engaged, wouldn't the binding be more severe?

 

[Edbert]

Now to my specific question-- if the torque converter wasn't fully engaged, wouldn't the binding be more severe?

Simple answer, no, at least not necessarilly.

I am intruiged by the rest of the story though. Why would bolting the engine to the tranny prevent it from turning? Where was the contact?

 

[mustangdave]

I would pull it part, triple check the convertor and mark the flexplate with grease or something and find out where and why it is hitting something with one block plate. If the t.q. is not engaged your car may go nowhere and you could ruin the pump.

 

[thehueypilot]

I had the same problem and ruined the transmission. You have a C6 flexplate mis-packaged in a AOD wrapper from the factory. The C6 flexplate is identical to the AOD except the offset (depth) is about 1/8 to 1/4 deeper which causes the flex plate to rub on the front pump housing of the transmission. Don't run it like that!

 

[jshcobra]

Simple answer, no, at least not necessarilly.

I am intruiged by the rest of the story though. Why would bolting the engine to the tranny prevent it from turning? Where was the contact?

Well, I went for broke and fired her up, hoping for the best. Seems to be ok. I believe the extra thickness of the flywheel was pushing the converter back against the pump housing. From what I've read so far, there is supposed to be a slight bit of clearance between the converter and the flexplate when you bolt the bell to the engine. Judging from the difference in flexplate thicknesses, I think that clearance was used up by the thicker flexplate.

Of course this is just a hypothesis, but I'm going to give 'er a go and see how she does.

 

[Edbert]

Well, I went for broke and fired her up, hoping for the best. Seems to be ok. I believe the extra thickness of the flywheel was pushing the converter back against the pump housing. From what I've read so far, there is supposed to be a slight bit of clearance between the converter and the flexplate when you bolt the bell to the engine. Judging from the difference in flexplate thicknesses, I think that clearance was used up by the thicker flexplate.

Of course this is just a hypothesis, but I'm going to give 'er a go and see how she does.

Anything to report?

The reason I'm so curious is that I have been hand cranking my engine over every few weeks for some time now (in addition to running the oil pump with and electric screwdriver) but since I've bolted up the tranny it is VERY tight to turn by hand.

 

[jshcobra]

Well, it's been about two weeks of driving now with the AOD and the double-spacer solution seems to be working. I suspect I would have found out if it didn't by now.

The only problem I have noticed is that whenever shifting into drive or reverse from park when on an incline, it takes 30-45 seconds to build line pressure and actually go into gear. Once it does, it shifts and operates fine. I doubt this would have anything to do with setting the transmission back. More likely, its because this is a used tranny that's probably seen some neglect in its life.

 

[Edbert]

You may be low on fluid, you aren;t using the dipstick from a C4 are you?

Did you ever find out where the binding was coming from?