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post #1 of 4 (permalink) Old 10-23-2010, 08:49 PM Thread Starter
 
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Th400

My '68 GTO has a TH400, which shifts as it should. It is smooth w partial throttle, & chirps the tires at WOT. Feels good!

However, it "freewheels" in 2nd gear. Is that normal, and if not, what would cause it?

It decelerates in 1st and 3rd, but just disengages in 2nd when I let off the gas.
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post #2 of 4 (permalink) Old 10-24-2010, 02:12 PM
 
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If it did it in all gears, I would say it's the vacuum modulator. I don't know, probably ready for a rebuild or something is sticking in the tranny. Throw some Lucas tranny stuff in it, maybe it will free it up.

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post #3 of 4 (permalink) Old 10-24-2010, 04:43 PM
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Quote:
Originally Posted by dhinnah View Post
My '68 GTO has a TH400, which shifts as it should. It is smooth w partial throttle, & chirps the tires at WOT. Feels good!

However, it "freewheels" in 2nd gear. Is that normal, and if not, what would cause it?

It decelerates in 1st and 3rd, but just disengages in 2nd when I let off the gas.
Mine does none of the mentioned even when shifting through the gears. Even when the transmission was abused and worn out it did none of the above.
You should be able to feel the power from one gear to another. Total rebuild is in the 5-600 range.

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post #4 of 4 (permalink) Old 10-24-2010, 05:43 PM
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Does it freewheel when you put it in manual 2nd? If so, it could be the band or the accumulator piston that applies the band....lack of fluid pressure, burnt band, etc. Lack of pressure to the piston causes slippage and burn out. If it freewheels at all times, it could also be a one way sprag gone bad. How's the fluid? Burnt or clean? I'm afraid at least a partial teardown and inspection may be needed.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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