I am putting a C-4 into a 91 mustang and have read the thousands of write ups on this and didn't find anything on these issues. First when I bolted the trans up I could not turn over the motor with a wrench I had to loosen up the trans a little bit to get the motor to turn. Is this normal or is somehting wrong? I used a c-4 from a 65 mustang with small bell housing so I got the 157 tooth flexplate the convertor also came out the same car so I fiqured the convertor was for the 157 flexplate so I don't think that is the problem?? But not sure. The other problem I had was that i used the block plate for the AOD and it is too big and the starter doesn't fit. I trimed the block plate to make the starter fit. The question is do I have to put a plate between the starter and the trans or can I just leave it bare? I can make a little plate if needed or can I put something else there??
Sounds like the convertor is not seated in the front pump, when you tighten the bell housing bolts will the convertor still wiggle in the flexplate. It should not be putting any pressure on the flex plate at all, you should be able to push the convertor at least 1/4" back from the flexplate. If it's bound up you may have damaged the front pump in the trans.
Another problem I see is you have a 91 engine, if I remember correctly they are 50oz balance, the 65 is 28oz balance so even if you do get it runing it's going to vibrate it's self to death.
You do need the block plate thickness behind the starter.
I bought the 50oz 157 tooth flex plate so I am good there. The converter doesn't move at all. I don't know much about transmissions what is the 1st pump? I put the drive shaft in and the trans turns over just fine in nuteral not sure if that matters. I read that the converter should move even when you bolt it down, but it was talking about studs and I dont have studs it just bolts to the flexplate.
What I am saying is the convertor should be able to float when it is unbolted from the flex plate, since yours has bolts instead of studs try to loosen the bolts and see if the convertor can be pushed back 1/4" toward the trans. It should not put any pressure on the flex plate at all when the bellhousing is bolted up to the engine.
If the convertor does not float it either is not seated in the trans or you have mismatched parts, there are 2 sets of splines and the punp drive on the convertor that must mesh before the convertor seats properly. Some people call this the 3 click seating, when installing the convertor into the trans you should feel 3 distinct drops as the splines and pump drive line up.
You did install the convertor on the trans first, it will never line up if you bolt it to the flex plate then try to install the trans.
Check out the float and let us know what you find.
1) You must use a separator plate (block plate) between the bell and motor. If you don't, your starter will eventually break your bell housing.
2) If you bolted the converter to the flexplate BEFORE you seated the converter in the transmission, you probably ruined your pump. Converter must be seated in the transmission BEFORE you lift the transmission to bolt it to the motor. Converter bolts are the LAST bolts to be installed.
3) Turning the driveshaft tells you nothing. The output shaft is not connected to the input unless the motor is running and the transmission is in gear.
Thank you for the help I will check to float tonight. I am getting to the point where I don't think the converter is seated properly. The convertor and the trans came from the same car so I know they are the right parts. The only thing that is not is the block plate but I will fix that.