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TH400 Question

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Old 05-23-2007, 05:57 PM
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Im not sure you guys will be able to help me but it's worth a shot. Anyhow my dad just bought a 1970 Olds 442 with a 455/TH400/12 Bolt. When we 1st got it it shifted really hard, I mean it jerked you around bad. We swapped out the vacuum lines and the modulator and it pretty much fixed the shifting problem, I guess it was leaking or the modulator was just bad.
Anyhow the problem is when you are in park, and you go to put the car in reverse or drive it will jerk really hard. Pretty much feels how it did when it used to shift hard but it only does it when you go from park to R or D. Does anybody have any ideas or fixes for this problem. Thanks.
Old 05-23-2007, 10:34 PM
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High line pressure will cause that. Fast idle will cause it too.
Old 05-23-2007, 11:03 PM
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do you have the vaccum on part time if not thats your problem...or try a adjustable modulator
Old 05-23-2007, 11:11 PM
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Actually in late h400 they fixed that but it is relatively normal for early models
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