1965 gran sport 400 tranny upgrade

[Robin Cook]

What is required to upgrade stock  th300 to a 65 th400? My first roadblock was stock floor shifter does not fit!

[WkillGS]

Shiftworks has a cable operated kit to adapt the stock 2 speed shifter to the 3 speed ST400.
The 400 trans is longer, so you will need to add some brackets to the frame to mount the crossmember to. The extra length will also require a shorter driveshaft. The smaller ST300 converter will fit the ST400. Some big-car flexplates are only drilled for the big converters, but most have the dual pattern by 1966.
Trans cooler lines need to be changed too.

[Dr Frankenbuick]

Also, the 400 has a larger yoke and the trans mount is different.  You can modify the mount to work or get one for a 400. 

[GreatScat1965]

A stock 1967 shifter will work if you can find one. Minor floor cutting would be required.

[GreatScat1965]

A 67 PRNDL will fit as well

[WkillGS]

Also, the 400 has a larger yoke and the trans mount is different.  You can modify the mount to work or get one for a 400.

There is a large (OD) diameter yoke and a small diameter yoke (aka thin yoke) for the ST400. It depends on which tailhousing is on the trans.
I'm hazy on the details, I think the early ones had small OD.

[Robin Cook]

Thanks folks! I’ve put a lot 65 trans from a wildcat in the car, all fitted and good so far, I have a 67 shifter so will see how it goes, so anyone have a template, as I see 67 has to mount further back from stock.

[Lou Perfetto]

Robin,
How did the swap go? Should be pretty straight forward with some mods. Putting a 3 speed in your car will be a Fantastic upgrade. Going from a 1.76:1 1st gear to a 2.48 will really make your car come alive. Also did you use your ST300 convertor instead of the one from the 400? It will give you a 3000 stall instead of the 2300 the 400 convertor will give you. In 1980 I had the awesome opportunity to talk to Tommy Ivo, the Nailhead King of the time. I called him at his shop in California and we talked twice. The first time for a half hour and 15 minutes the second. I needed advice on tuning and racing my 65 Riviera GS 2x4. He went off for a bit on Buick for not putting the ST400 in the Skylark in 65. He said if they did, the Beach Boys would have been singing songs about the Gran Sport instead of the GTO. Anyway, he explained the convertor swap and tapping into the stator switch with a momentary button taped to my shifter to stall the convertor at the line. With the 3:42 rear and ST400 convertor, 2300 stall the 4000lb Riviera got up and went. Hold the button half way thru 1st gear and then let it go. You will need more tire.....  

[Robin Cook]

Hey Lou

Yeah the swap out was pretty straightforward, ended up using my original consul of the 65, the modification cable kit from shift works is perfect! Nice touch on the PRNDL glass.

So it’s now running, still need to get exhaust installed interior finished, but hey I have a driver seat! Lol.

I’m running into a problem with vibration, it’s a balancing issue somewhere, I’m going to check my firing order hoping that’s it. If not I will disconnect the converter to flex plate and try and isolate. Very strange as I had no evidence of vibration when I broke in that engine on my engine run stand. Is the flexplate and converter clocked? Or are there various positions? Any ideas? I’m pretty sure I used the 300 converter, but I really can’t remember? I’ll have the inspection cover off shortly, anyway to tell? I am running that manual switch pitch to my dash area, hidden of course, Be nice to have a cruise control signal arm lol.
Really cool dual quad factory set up on my car, only thing not original is the air cleaner, which I wouldn’t use anyway as it covers up all the pretty stuff!
Great to chat with you Lou, hope all is well, keep in touch friend.

[jmos4]

Hi,

You might want to check you driveshaft angle as moving the crossmember back may have lowered the trans output changing the angle, so you may have to shim the mount.

Regards,
Jim

[Robin Cook]

Hey Lou
Vibration is static. Not while moving. I should have been more clear. Any idea?

[Lou Perfetto]

Hey Robin,
That was Jim that replied. The flexplate and convertor are not clocked. I would unbolt the convertor from the flexplate and push it back and check for anything visually wrong. Was the convertor spinning freely after you bolted the tranny to the block? 

[Robin Cook]

Hello,

Yes the converter did spin freely, car moves back-and-forth no problem, I just have a nasty vibration, should have an opportunity to check the firing
 order tomorrow the only other thing I could think of

[Dr Frankenbuick]

The flexplate will bolt up in 6 positions, but it is only right when the index holes are lined up or almost lined up using non-original parts. Did you have the flexplate off after running the engine in?   

[GS66]

One of our 66?s has a TH 400 in it and when I had a vibration it turned out to be the flex plate was bad.