Best source for purchasing TH 400
 

The TH 400 in my 1969 Firebird lost its ability to shift into low/1st. From a stop, in Drive, it starts in 2nd and shifts to 3rd. It will not shift to low manually.

It was a used transmission when I acquired it many years ago.

I just want to put in a transmission that will shift correctly and doesn't leak.

The car originally had a TH 350 and I don't have the kick-down switch. Which switch is supposed to be installed: carburetor or gas pedal?

Where can the switch be purchased?

Your T400 should be a easy fix. I have rebuilt several with the Ron Sessions book. If you are handy at all you can do it.

Not sure where you’re located but Jim Hostler in Delaware is as good as it gets and reasonably priced.

I bought Cliff's book but my confidence and track record doesn't convince me that fixing it would be a better option than buying one fresh.

I am in Las Vegas- not so close to Delaware
So I suppose the ones on Summit or the like are not a wise choice or money well spent?

I have no experience with Summit or Jegs transmissions so can’t offer advice there.

alot of racers there in Vegas. When looking for stuff..I always recommend the local drag strip....walk and talk to folks. Local is always a good source on big items. Yes buying one in a box works 95% of the time....guess what YOU would be the 1% failure then trying to coordinate shipping ...blah blah blah. Sine you are only building a mild 400 that should be candy to most any tranny builder. FWIW it should NOT cost you $2000 either! (provided you R&R it)
Kickdown switch should go on carb,,,provided you have a Q-jet. BUT any snap switch will do...pedal or carb.

https://www.ebay.com/itm/350482022728

I would probably just call a local transmission shop. TH400s should be on the menu everywhere. Call two or three, tell them you want a performance build and go with who you like best.

FWIW I also swapped in a th400 into my first gen, never bothered with the kickdown switch. It really just never comes into play. If I ever need to I just manually shift to second and hit the gas. More fun that way anyway. Even then, I think Ive needed to do that maybe 10 times ever. I think the kickdown comes into play more if you have an OD transmission.

I still build the TH400s, local only. Plenty of hard parts. Resto/Street/Strip, no boosted/nitrous/lineLocks.

best bet is to call a local trans shop & have yours rebuilt, should be very reasonable if you pull the trans & bring it in to them. i just had a th350 rebuilt locally for less than $500 & that included the name brand rebuild kit. would be a good time to buy a new converter too if you want to get a little more performance out of it. or check craigslist or FB marketplace for another used one for a few hundred bucks but thats a gamble as you found on your current used one.

as for the new ones from jegs or summit, they are usually good units too & will have a warranty of some kind, but a new one from b&M or TCI will be a quality rebuilt trans, i have a TCI street fighter TH400 behind a 500+hp stroker engine that has been doing great & shifts very firm, supposed to handle ~700hp. they are a little more pricey at $1000+ but that includes the trans with no core charge. theres a few other companies that sell them new/rebuilt too.

The kick own switch on my 67 Catalina was on the gas pedal linkage on the floor board.

TH 400 Transmission Problems
 

My 69 GTO will not shift into low manually but when it's in drive it goes through all the gears. As far as your car not shifting into low it could be your shift cable is stretched and you may be able to adjust it or buy a new one . On page 7G3 in the 69 Pontiac Service Manual is the procedure for adjustments with the transmission in the car. Also you may be able to adjust the selector lever position.

Carousel72TRed

There is no easier automatic trans to rebuild than the TH400. All the gears in back, all the clutches in front, and generally strong and reliable with no hateful "known problem areas" in normal or moderate performance use.

If reverse and high gear work good, this could be an easy valve-body or governor issue. No need to even remove the transmission. May have to unbolt the valve body, or pop the governor cover off. I'd start with the governor.

Best source for purchasing TH 400
 

I can tell you I've had my GTO for 42 years (bought it from shipmate when I was in the Navy for $750) and the only thing I ever did to the transmission was put a B&M shift improver kit in it and changed the fluid a couple times. I am hoping that all I will need to do for it to shift manually into low is follow the procedure for adjustments on page 7G3 in the Pontiac Service Manual or install a new shift cable which I have.

Carousel72TRed

"Catching Low" or "Grabbing 1st" is likely a shift cable deal, along with bracket clips done right. Our Pontiacs usually had an adjustment at the TH400 Lever: pin/slot.

Starting in 2nd gear is totally different from not being able to cram the shifter into Manual Low.

Adjust you linkage/ shift cable and go from there. Start with the basics.
Jack it up, get under there and have someone go through the gears and find out if everything is where its supposed to be. Put it into 1st, pull the cable out of the hole and see if its is centered.

There is nothing in the shift linkage that will cause a TH400 to start in second gear instead of first gear.

Agree that I’d look at a rebuild local over buying a completely new trans. You’ll be money ahead.

On a 1969 bird the kickdown is a plunger switch attached at the throttle cable on the carb. Nobody makes a reproduction and if you can find an original, used or NOS, you’ll pay a premium for it.

What I did with the switch is used the B&M universal th400 kickdown. I had to cobble together a mount using a TV cable mount that allowed the throttle to pull the switch. Not too hard and much cheaper.

Is this a question or statement?

I have been searching for a reason for a while. I even followed instructions to troubleshoot the governor. It was not stuck or sticking when I removed it; all parts moved freely.

I checked the shifter cable. I even removed the shifter to insure that the cable allowed travel from park to low position on transmission.

If anything, I thought that driving without the kick-down switch connected caused a problem.

I cannot manually shift into low while driving. It will shift from drive into second speed only.

If it does start off in 1st/low, it is not detectable to me. I only feel and hear it shift once.

The engine is a 428 with 68 intake and 77 quadrajet. It used to have 041 cam and 4.10 ratio. I removed the Moroso Brute Strength for a 3 series carrier and now use 3.08 and 068 camshaft. It should still start from a standstill with good effort. My Saturn L200 feels like it has more pull.

That's why I was asking about over-the-counter replacement to install.

I used to go to Dudley's Transmission. Somebody else owned it and was in North Las Vegas but they shut down.