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Discussion Starter #1
New guy here, but not new to cars at all. I'm primarily a classic Pontiac guy.

I picked up a '69 Fairlane 500 Fastback to restore and give to my father (his favorite body style when he was growing up). The car hadn't run in 30 years and the 351W engine was seized when I purchased it. I pulled the engine and had it rebuilt back to stock specs. While the engine was out, I checked the transmission fluid and it looked great, so I didn't rebuild. Instead, I drained and flushed the torque converter (OE from 1969), FMX transmission, replaced the lines and radiator. Then I re-filled with Ford type F transmission fluid. I got the engine back and dropped it in. 13 months later, it was finally all back together and runs like a top.

When I start the car and move the selector to any gear, the transmission goes into gear hard and kills the car about half the time. Once in gear, it seems to want to move the car much more than it should. If I park against a parking block in a rock driveway and let off the brakes, it will spin the tires in rocks. I have to apply quite a lot of brake pressure to hold the car in place. It seems to drive fine and shift perfectly, but when I come to a stop, sometimes the car dies as well.

The idle speed is right by RPM. Turning it up only makes it shift even harder from Park/Neutral into gear. Turning it down makes the car die instantly every time when I put it in gear.

To me, it seems like the torque converter is way too tight... But before I go out and buy a new one, I wanted to ask here. Has anyone ever heard of torque converters tightening up over time? Usually they slip/get too loose when they go bad. I can't imagine the car drove like this when new or the original owner would've been upset.

Thoughts?

(Pics for attention)
 

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Discussion Starter #2
I'm won't even begin to act like I know what goes on inside these transmissions... But could it be a bad vacuum modulator, attempting to keep line pressure too high and making the torque converter work harder?
 

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Thanks for that. #2 is quite useful. I'll make sure I have good vacuum at the vacuum modulator, and replace the modulator first. That's a cheap part and much easier to get to than the torque converter. I'll let you know how it goes this weekend.
The modulator is quite rusted (original from '69), but it works. I verified it does not leak and verified it reacts to vacuum. I can't figure out why it shifts so hard from P/N to R/D.
 
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