340 TH400 Question

[Tinny]

Hi Guys,
Just a question. Will a BOP TH400 fit up behind a 340 (in a 66 Lesabre convert)?
And if it will, what else will I need to replace or modify, tailshaft / crossmember?

Either that, or maybe replace the whole engine/tranny package with say a 455/TH400, still assuming I'd have to swap/modify the tailshaft etc
Is that a pretty easy swap?

Thanks.

[Dr. Frankenbuick]

You need the driveshaft from a 66 or 67 Lesabre 400. That is Lesabre with a ST400 already installed behind a 340. The crossmember will need to be moved backward and you will need a 400 transmission mount. You would also need the transmission yoke for the TH400 since it has a larger diameter then the ST400 yoke.


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[telriv]

In my opinion you'd be better off with a TH350 or a 200r4. They are the same size as the TH300 that's in there now. No mods needed other than linkage. For all intent purposes a bolt-in swap nearly.

[Tinny]

Thanks Tom.
That sounds like a better option.
I'm in Australia, so finding all those other parts for a TH400 swap may be relatively easy in the states, but finding things like a tailshaft here would be next to impossible.
Main reason for the swap would be for a bit more driveability & economy. The 340 seems ok, but the two speed tranny is pretty ordinary.

Thanks for the input guys. I knew folks would be able to help.

Cheers.

[telriv]

Your initial get up & go would be better as the 1st. gear ratio is 3.52-1 as opposed to, I think, 1.82-1 In reality the 2spd. with the "switch-pitch" working is not all that bad. As for fuel economy the final drive ratio is still 1-1 on either trans except of course the 200r4 which has the overdrive. BUT, to get the MOST out of it you would have to change the rear gears to AT LEAST 3.42, 3.73 more preferable.
Does your switch-pitch work???

[Tinny]

Hi Tom.
To be honest, I'd never heard of a switch pitch until Tony was here when we did the brake kit. I thought the unit on the manifold was for cruise control. It was disconnected when I got the car.
Tony told me what it was and how it works, we played around with it, but couldn't hear a solenoid in the tranny working, so at a guess I'd say it doesn't work. Finding someone here in Australia who would know how to get it working would be impossible, thats why I reckon a change to a TH400 or the simpler swap to the TH350 would be the go.
It (the tranny swap) is something for the future. At this stage I'm just working to fix lots of small things, then the big job of replacing the roof and a paintjob will be for when it starts warming up.

Cheers.

[telriv]

There's plenty of posts here & on v8buick about how the switch-pitch works & how to adjust & repair it. It will make a WORLD of diff. in the performance of the car & it's NOT hard to do.
Do a search on switch-pitch.

[Bob]

There is an entire 1966 Chassis Manual in the Reference, it covers the transmission.

Having the switch pitch working is like doubling the number of gears available.

[Tinny]

Thanks guys.
I'll check it out.

Cheers.

[fatbuick]

The solenoid could be okay and just the wiring could be faulty.
It may not even be connected to the tranny with the plug on the side.
Check the terminals on the kickdown and see if there's any juice getting to that point.
To check the solenoid you could touch the terminals on the side of the tranny with a temp wire from the battery + side
I'm not sure which of the two terminals is for the solenoid.