Howdy! I haven't been on much, as I've actually been in the garage doing things. One of those things is swapping a flexplate for one with better teeth. I have a '64 Cadillac 429 and a first year switch-pitch TH400. Cadillac used a factory transmission adapter that year on the TH400 models (from Buicks), as they didn't want to re-tool the backs of the blocks. The flexplate is supposed to be one-year-only, as there's a raised 3" flexplate mounting area. I've heard other year flexplates COULD be used, but I went ahead and sourced another '64 one for this swap. When it arrived, it has some mysterious holes in it that my original doesn't have. If I use it, will it throw off the balance? The '66 I have also has the same holes. The ring gears are the same - should I just have a machine shop swap 'em with my original and be done? Here's some pics. ~Jason The left is a '66, the right is supposedly a '64, and the center is my original.
The holes in the later other flexplate would be because the flexplate was out of balance. At least that is what i would think. Cadillac didn't make an external balance engine in that time period as far as i know. If you can afford it just take it to the machine shop and have them switch the starter ring that way you won't have to stress over it.
The drilled holes just inside of the ring gear are from when the flexplate was balanced at the factory. Not sure on what you need to hook the thing up right as I never had to contend with that issue.
Thanks, guys. This is exactly what I had thought (that they were for balance) and what I thought I should do (ring gear swap). Y'all rock! The HAMB is always good for a second opinion! ~Jason
I mentioned the starter ring swap for your piece of mind. The balance holes are because of the flex plate being out of balance not for engine balance. Either way you should be fine, swap the starter ring or just bolt the other flexplate up.
If you look at any bandsaw pullys and other equipment they will have the balance holes also .So x3 on the good answers............YG
Just a note on the SP TH400: get a GOOD cooler. Those converters make a LOT of heat, more than the TH400 will like. I know this for fact, sadly. I know the factory put this together, and they probably did a good job engineering the cooling. And I know they quit after three years. Mayhaps too many warrantee claims?? Too easy to put on an 8 row or better cooler. Cosmo
These guys seem to be the only guys in town that would tackle this: http://www.laynemachine.com/ ~Jason
I would just bolt up the one in the best shape and go and not worry about it, because if you change the ring gear the damn thing has to be balanced all over again and you'd have to drill holes in your old one just like one of the other two.
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