Inliners International Forums General Discussion Drive Train powerglide swap

I am looking to put in a th350 in place of a burnt out powerglide. It is going into a 1964 Pontiac Acadian, and behind a turbocharged 250. The motor does not make all that much power but I want the trans to hold together longer than my 2 speed did. Am I going to find any surprises along the way, or is it a fairly straight forward swap? I am already looking at a new linkage setup from Lokar, as well as kickdown linkage. But are there any other surprises that anyone knows about?
Any info would be great
Thanks
Rob

x-member and trans mount location may change, not to mention that u may have to have the driveshaft shortened or lengthened.. a quick measurement of each trans will help (front of bell to end of extension housing) determine if ur driveshaft will work.. be careful to check the splines on the output shaft., u might also need a driveshaft yoke.. gl!

The trans mount and crossmember will be fine. I would recommend a new trans mount simply because the original may be oil soaked and weakened or dry rotted. Mysterious vibrations are often caused by a bad trans mount. They are about $20 new. The drive shaft will require a new front yoke due to the 2 trans having a different number of splines. New yokes are about $65. The driveshaft will most likely be about 2 inches too long and should be professionally cut and rebalanced. The driveshaft shop will tell you exactly how they want you to measure your car and they can also provide and install the new yoke.
Check the convertor to flex plate bolt holes. If they don't agree you will need to replace the flex plate. Some plates have 2 sets of convertor holes and others only one so replacement may not be needed if your has both sets.

The trans swap is a nut and bolt job you can do and when you get the driveshaft back all you need to do is install it.

The Powerglide uses a mechanical kickdown linkage and the TH 350 uses a cable as you already know.

even though some gm flrxplates have 2 sets of holes for the converter, they r the same measurement... it wont matter.. the flexplate u have will work fine.

There are different lengths of TH350's. The one you want is a short shaft and you won't modify anythink for the cross mmember. You may want to look at http://www.angelfire.com/nv/conv/ and click on swaps.

Thanks for all the info and links, they are a good help, but more questions came up. Is it possible to install a short tailshaft onto a trans. that already has a long shaft on it? I had a th350 given to me with a 9" shaft on it, and to get away without cutting the driveshaft I need a short tailshaft. Also, Mike G had stated that the yokes were different, spline count, but in the website that Walt 1940 supplied, it looks like they are the same.

Rob,
If the trans in your car is a 1964 the splines
will be different than the TH350. The course spline tail shafts were used thru 1966.
The tail shaft can be replaced with one for the
6 inch tail housing, but the trans will have to be completely taken apart to do it.
Gordy

You will need to notch the flange on the front of the transmission crossmember to clear the TH350 oil pan as well as the other issues mentioned in this thread.

Let's go back to the top for a moment and see if we can simplify this for Rob.

1. If your trans is a 1964 Powerglide then you will have to use a TH350 27 spline yoke. This yoke also fits all the fully synchromesh 3 and 4 speeds except the M22 Muncies and TH400 automatics. It is an on the shelf item at any driveshaft shop and also by mail order. There is an early style with the retaining snap rings on the outside of the bearing cups and a later style that has them inside, otherwise they are identical. Get the one that matches the yoke welded on your driveshaft. Should be the early style external snap rings.

2. A TH350 with a 6 inch tailshaft is for all our purposes the same length from the back of the block to the rear seal as any of the fully synchro Muncie 3 or 4 speeds and Saginaw 3 or 4 speeds when also measured from the back of the block to their rear seals while attached to the bellhousing. All have the mount the same distance from the back of the block as does the P'Glide.

3. The P'Glide is about 2 inches + - longer overall than the TH350 or standard shift set ups and some driveshaft work will be needed.

What Gordy points out is correct for changing to a short tailshaft. TH350's are almost a dime a dozen and there are tons of 6 inch units out there. Might not be worth the trouble and expense to have a shop do the work. Usually they will want to go through the whole trans if they are going to have to stand behind it. If you have done auto trans rebuillds then you should be able to handle it yourself.