Powerglde to THM 350 swap

Halfway through swapping in THM 350 in place of the original Glide & no real "glitches" yet. Anybody who has done this swap have any tips or tricks to keep this moving along? Have the old tranny out & cleaning up underside a little , waiting a few days to a couple of parts to arrive. Thanks in advance

 

Bump

 

You didn't mention what year your car is, but I did that swap in my '64 Skylark last summer. Physically it was a bolt in fit. I had to bend the transmission cooling lines a bit, but very little. And that could have been caused when removing the old engine and transmission. The vacuum line going down from back of manifold to transmission needed a little tweaking, but may have been partly because I was also swapping the 300 engine for a 350. The biggest problem for me has been figuring out how to make the kickdown operate. Still haven't tackled that one. If your car is newer, and has the kickdown and throttle cables going through firewall to throttle pedal, it shouldn't be too hard I would think. That type hook up is what some of the guys on this board have recommended.

Good luck!

 

Measure the length of the th-350, only some of them are the same length as your 2 speed 300 trans.

 

If you have the car the transmission came out of? It should have everything you need for the swap.

Bob H.

 

Some of
The info on my car is as
Follows; it is a 1968 skylark custom conv purchased from original owner 3 yrs ago. The car was assembled in Wilminton . The car is mostly stock w/ 1 repaint. The drivetrain is a 350-4bbl with a ST 300 ( sorry for that egregious error) and a 2.56 peg-leg The tranny I'm replacing it with is freshly rebuilt unit w/a shiftkit & slightly smaller converter. The core from the tranny I will be using I got from Bruno D senior . Little problem so far removing the 300, I'm doing in my garage on my back, just don't want any glitches to arise down the stretch

 

I thought all BOP THM350's (short tail ) were the same ?

 

Yes the short tail is the same but the medium and long tails are longer.

 

Thanks Sean I was told conflicting answers as per moving the crossmember and is it the same for both trannies. What is your thoughts on the driveshaft , bolt in or need to be shortened ?

 

I must have been wring on my recolection of the cross-member placement. The driveshaft should not need to be modified.

 

I was under the impression you only had to move the cross member when going to a TH-400?

 

My crossmember fit the TH350 in the original location. Drive shaft bolted right up. Yoke fit also. Bell housing and dowels matched the 350 engine. If I remember right, I used my transmission mount from the ST300 because it was in like new condition, just needed cleaned up. I assume the previous owner had replaced it since the car had 126,ooo miles on it at the time. My understanding is the torque converters do not interchange from the ST300 and TH350.

 

They are interchangeable if the st300 is from a '68 car which IIRC was the last year for the st300 or was it '69, it was the last or one of the last years of the st300 when they were in transition to changing over to the TH350. Those year(s) the converters were no longer switch pitch converters and are interchangeable with the TH350.

 

Thanks for clearing that up. I didn't know there was a ST300 that was not switch pitch.

 

I was told the linkage ( column shift ) shouldn't be an issue when going from a 2 speed to a 3 speed. Original linkage is a little loose/ sloppy, anybody know what to do to snug it up a little. Looks like the one bushing on the bottom is shot. Are there any other ones & who if anyone sells them ?

 

The column shift linkage worked on my car. We had to adjust the linkage travel where the rod coming down from the column mates up with the arm to the transmission. Goes into park and all the gears fine. Just doesn't read correctly at the gear indicator window.