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Canadian Poncho Homepage -> Canadian Poncho -> Beaumont Power Train Tech Forum -> TH400 shifting problem? I don't know?
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vicfire


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TH400 shifting problem? I don't know?
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Hey guys, so when I first drove my 67 it was loosing major vacuum pressure from a blown brake booster, I had a low RPM mini backfire going on and she idled a little high but other than that it was running pretty good.  The car has a TH400 with a B&M shift kit in it. I could start out in 1st then push it into 2nd at any rpm and it would shift right away no prob. Now that I have fixed the booster so I have no more vacuum loss I start in 1st and if I push it into 2nd she wont shift until I hit 3800 RPM with a big old chirp and smoke puff. I don't mind this too much but when I am cruising home from work in the am it would be nice to be able to shift a little early to avoid waking up the entire neighborhood.
I guess my question is, would the change in Vacuum pressure cause this? It is the only thing that I have done to the car since I bought it.
Thanks

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beaumontwagon


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Sounds like you might have to readjust your modulator on the trans with a small flat screwdriver.Stick it in the hole and turn counter clockwise to make it shift earlier.Youll have to experiment a few times to get it where you want.

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Ghost Post


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Also is your kickdown working properly?.
Symptoms sound similar to what happens when the kickdown systems are stuck on..

Good luck!.
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vicfire


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That would make sense, I'll have to check that.
Thanks

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vicfire


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So all wire running from carb switch assembly to kickdown on trans is connected and is supplying power. Could the solenoid on the trans have failed?

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beaumontwagon


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Did you check the modulator on the trans?

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vicfire


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going to check that out tomorrow.

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67Poncho


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vicfire wrote:

So all wire running from carb switch assembly to kickdown on trans is connected and is supplying power. Could the solenoid on the trans have failed?


Is it supplying power all the time?? It is only suppose to when you are in "kickdown" mode. Disconnect from the trans, if it is, and test drive it... It should upshift normally...

 



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vicfire


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So problems solved, traced it to the vacuum line running from the intake to the modulator. There was a large hole in the line where it was rubbing against another line. No vacuum = late and hard shifts. Ran a new line and she is as smooth as can be.
Thanks guys for the help.

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427carl


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