Th 400 transmission kick down

[Red71gmc]

I am not a transmission guy as you will be able to tell. From my reading of old post I think I can handle my two issues with a little more info.

I have a 71 GMC with a TH400 transmission. I have a couple things I would like to correct. The first being it doesn't shift down from 3rd when hard pedal is applied. I don't have a kick down switch on my gas pedal but it does have the mounting plate for one. I can get a switch and wiring but where does it hook up at the transmission?

The other is the quick shift from 2nd to 3rd at lower than desired speeds. I have read several old post about that and believe I need to try to adjust the vacuum modulator screw first (if supplied) and then maybe a shift kit.

Should I fix the kick down first? Or does it matter? Thank you

[Sawlog]

I have a th400 in my 69.
I put my kick down switch on my intake manifold a hooked it to my carb.
Works great. The wire hooks to the driver side of tranny behind the shifting linkage.
As far as you shifting, screw on the screw on the vac mod. Try a little at a to e and test drive it.

[Red71gmc]

Thanks for the location on the transmission. I'll take a look and see.

[LockDoc]

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Read this thread and check out the link Tim included in post #6.

http://67-72chevytrucks.com/vboard/s...d.php?t=661922

LockDoc

[Red71gmc]

Re: Th 400 transmission kick down
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Read this thread and check out the link Tim included in post #6.

http://67-72chevytrucks.com/vboard/s...d.php?t=661922

LockDoc

Thank you, very helpful. It appears to be somewhat easy as long as my cylinoid is good in the transmission.

[Red71gmc]

I may be bumping my own post but I see your specialty LockDoc.
If I don't have a key for my door locks can a locksmith key them? Do they need removed? Am I better off to get new ones? Thanks

[LockDoc]

Originally Posted by Red71gmc

I may be bumping my own post but I see your specialty LockDoc.
If I don't have a key for my door locks can a locksmith key them? Do they need removed? Am I better off to get new ones? Thanks

The door and ignition locks were originally keyed the same. Have you tried squirting some penetrating oil into the door lock cylinders? Someone may have changed the ignition lock at some point in time too. If you don't mind if the doors and ignition don't use the same key, a locksmith should be able to make a key for the door locks. You will have to take one of them out of the door. Start with the passengers side. Once you get the lock cylinder out check and see if it has a code number stamped into it like the one in the picture below. If it has a code number a locksmith can cut a key from that..... If it doesn't have a code number a key can still be made by disassembling the cylinder and reading the wafers.

LockDoc

[Red71gmc]

The two are different now. Thanks for the info. Exactly what I needed to know.

[LockDoc]

Originally Posted by Red71gmc

The two are different now. Thanks for the info. Exactly what I needed to know.

No problem, let me know if you have any other questions.

LockDoc