Hey guys -- I've got a 460 w/ a c6 tranny. There is some kind of problem at the rear of the engine and it's making a terrible noise from the bellhousing. I'm working on pulling the transmission. In the process I have destroyed the nuts that bolt up the flexplate (the ones you access from the inspection cover on the transmission.)

These were 9/16" nuts but summit and rockauto.com are listing 7/16" bolts. What's with the bolts/nuts difference and does anyone know what I should be buying?

 

There are two different 460 flexplates, but the torque converter lock nuts are the same for both.

378941-S441 .. Torque Converter Lock Nut 3/8" -24 (3/8" is the thread size, not the wrench size) / Available from Ford.

Why buy online and pay shipping charges?

Whiz over to a Ford dealer, these nuts have been used for over 60 years with Ford-O-Matic - FX/FMX/MX Cruise-O-Matic - C4 - C6 - AOD, so most dealers will have them.

EDIT: These lock nuts should only be used ONCE.

If used over again, the nylon locking insert will be worn down, the nuts will back off the converter studs, causing the flexplate to wobble. This could be the noise you're hearing.

 

That makes sense. So 3/8" lock-nut with a 9/16" head, correct?

 

I have no idea what the head size is, parts catalog doesn't list that info.

Since I provided the Ford part number, you can get the lock nuts from a dealer, so why worry about the head size.

And read my post again, I edited in some important info.

 

Thanks! I'll hit up my dealer when I put things back together. The nuts were not backing off -- they were incredibly tight but two of them took significant heat and a chisel to knock loose. They will all definitely be replaced.

 

Yes, 3/8" thread nuts and bolts typically take a 9/16" socket/wrench.
7/16" thread nuts are typically 5/8" socket, but sometimes they are 11/16". In many cases the bolt will take a 5/8" socket but the nut will take an 11/16" socket. I have never understood why this is.
If you go to 1/2" thread nuts and bolts, they take a 3/4" socket.

Chris

 

Nuts are often made to take a larger socket because you need to have some minimum thickness around the hole through the middle of 'em in order to have sufficient strength. Bolts, not having a hole through the middle, don't have this issue...