I Was Looking At A 66 Chevelle For Sale With A Two Speed Powerglide And Was Wondering How Hard Would Would It Be To Convert It To A Turbo 350 Or A Turbo 400.i Am Assuming The Linkage Must Be Changed Depending On What Shifter Is Used.thanks For The Help.

Its a fairly common and well documented swap to the 350, a lot of the restroration houses sell the various pieces to make it work. Do a search and you will find plenty of information on it. Even google it.

This is something on my list of "one day" mods for my 64, but first I have to actually get it running again.

Of the two, converting to a TH 350 is the easiest. The TH 350 is the same length as the PG and will fit right in there without having to shorten the drive shaft. You will need to change the linkage and modify the shifter. As mentioned, there are kits to do this. You may have to change the cooling lines. I am not sure if they connect up in the same place on the transmission as the PG.

The TH 400 is a different story. It is longer than the PG. You will have to shorten the drive shaft and change the transmission cross member. The TH 400 also requires electrical connections for the kickdown or modulator (not sure which). I don't know what is involved with setting that up.

In either case, be sure to use the same speedometer drive gear as is in your PG - either reuse the old one if it's in good shape or get a new one of the same color. Otherwise, the speedometer will be inaccurate.

Of course, if you want to convert to a manual four speed . . ..

The TH400 also uses a different driveshaft slip yoke, whereas the TH350 uses the same yoke as the Powerglide...

I think the flexplate needs to be changed for either swap...

The TH350 uses the same speedo gears, but I thought the TH400 used a larger gear assembly???

From the factory, the TH400 is stronger and always came behind BB engines, I don't think the TH350 ever was offered with a BB. But with aftermarket parts, the TH350 can easily handle mild BB.

don't need to change flexplate

From the factory, the TH400 is stronger and always came behind BB engines, I don't think the TH350 ever was offered with a BB. But with aftermarket parts, the TH350 can easily handle mild BB.

I have a friend running an ATI TH350 behind a 540 ci BBC w/ spray in a '84 Regal that runs 9.xx@14x mph. No troubles. He had the car in the HR magazine pump gas drags the last 2 years in a row.

A stock TH350 will be fine for a street 396, IMO.