Technical > Dan Dishon's Transmission Den

Shimming torque converter flexplate mounts.

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I would like to make one additional observation about converter shims. I have found that as the shim thickness increases so does the likelihood that you will see fretting of the shims against the flex plate and the converter tab surfaces. So I put three small tack welds on each shim to keep them solidly against the flex plate. I also like to turn a small pilot on each bolt to aid installation. I weigh each bolt on a gram scale after machining.

What would be the minimum pilot engagement into the end of the crankshaft?
That's what lines everything up.

I've gotten by with 1/4" of engagement. What you don't want to see is the pilot bottoming out in the crank. That will lead to thrust bearing failures.

Draw 3D:
Make sure that the flex plate is not installed backwards, it should be marked as to which side goes against the motor.

On my initial build, the converter to flex plate gap was a little over 3/8", took it to Hughes and they built up the converter pad and now fits pretty good. As I replace the flex plate, I sometimes use washers between the pad and flex plate but not more of a combined thickness 1/16, I like to keep around 1/8" gap for the pads. I also use a thin shim between flex plate and motor for motor plate clearance and starter engagement.

Thank you all for your input.
I wound up with shimming to the high side of the recommended range.
As regards Frenchy's caution about fretting, I see I need to regularly make sure the bolts stay tight.
I think the convertor pilot engagement into the crankshaft counterbore is sufficient.
I ran the car last weekend, it seems good and nothing came undone.
I posted some video of my runs in the Front Engine Dragster section, check them out if you like.
Thanks again,


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