[carlk4728]

When I ordered the torque converter for my rebuilt th400, I was asked if I wanted a 3 or 6 pad version. So I peaked under my truck at the flexplate, saw 6 mounting holes, and based on that info I ordered the 6 pad. I guess I was wrong, though, because now that it's all mounted (yes, without verifying fitment) I see that three of the six mounting locations on the flexplate don't line up with the TC (they create a pattern that is of a smaller diameter than the six on the TC). I assume that this is to provide compatibility for two different kinds of three pad TC's (a small and large bolt pattern diameter).

So now to the meat of the issue: can I safely bolt this 6 pad torque converter to my flexplate using just three bolts?

[junior stocker]

Redrill the plate for the additional 3 holes. The six bolt converters were usually for bigger trucks/motor homes/diesel rigs. I don't think I'd just not not bolt them on, they may create a vibration/noise issue, and you'll be back under there again correcting it. Would they possibly exchange converters for you? You could also buy another flexplate already drilled for the six bolt converter.

[sirlotsoflovin]

Dont Redrill Anything! Just Put The Three Bolts In It,u Wont Have Any Problems,and Yes The 6 Pad Is Just For High Output Torque

[75chev4x4]

Had the same thing when I went from big block to small block, 454 used six bolts and the 350 only used 3, called the tranny shop and they said three is fine for the 350.

[MouseFink]

GM flex plates often have dual bolt spacing (6 bolt holes) to fit a torque converter with either a 11.50" and 10.75" bolt pad spacing. The TH350 and TH400 torque converters come with 3 bolt pads but may have either bolt spacings. If your flex plate only has 3 bolt holes and they don't fit the bolt spacing on your new torque converter, you will have to purchase a flexplate that has a dual bolt circle.

I went through this puzzle with my '91 S10 Blazer 4.3L V6 engine when I had the engine built with 350 Chevy forged pistons and internally balanced. The 4L60 (700-R4) transmission in my S10 Blazer use counter-weighted flex plates for externally balanced engines. When I had the engine built and internally balanced, I had to use a heavy duty (0.125" thick) 168 tooth flex-plate, 3" flange bolt circle for the one-piec e seal without a counter weight and was zero blanced.

My engine builder knew exactly which HD flex plate to use. He provided an ATI #915534 non-counter weighted dual pattern flex-plate to use with a torque converter that has either a 10.75" and a 11.50" bolt circle, 168 tooth starter gear, a 3" crank flange bolt circle and zero blanced.

[carlk4728]

Thanks everyone for the advice. I went with lovin's suggestion and just bolted it up with three bolts.

Maybe I'll find a powerplant that will justify the use of the dormant three pads down the road. So I guess, in hindsight, I'm glad I accidentally bought the 6 pad...one less thing to upgrade in the future!