White_Knuckles

Getting sleepy up here with most our Northern cars taking a long winters nap. Thought I'd put up what I'm mucking through for advise.

I know a trans guy who's moving and liquidating his shop. He's offering a rebuilt TH350 for $500 without a core. Not bad and his work is excellent including a shift kit and other enhancements.

I've got an ST300 2-speed now with a column shifter. The thing is healthy, I've got the electric kick-down (pitch shift) working but it leaks from some mystery place. I had him look at it, change the pan gasket and fluid but it always starts leaking again days later. He wasn't very excited about the ol' Jetaway and said: Meh, put in a 350 or 400R4 and get rid of that thing.

So, maybe he's right? Having a real First gear may be better for take-off and a 3 speed may run a lower RPM at freeway speed. The column selector may work without the third position where selecting L or 1 would be 2 or second but D would be normal drive. I'm guessing the mechanical shift detent points may be close? I have a 70's Olds 350 engine so the bell housing, flex plate and trans mount brace shouldn't be an issue.

What am I missing here? The trans tail shaft would be the common, long style. Would the drive-line need modification? Is the column shift selector possible or should I assume a floor cable shifter will join the party? The speedometer gear drive and cable adaption may be a challenge as unknown how many differences are hiding here. I think adding a cable kick-down is straight forward. A flex style dipstick/fill tube will be a must I'm sure.

Any tips or tricks would be helpful. I dislike going into an "upgrade" and making things worse. I'm avoiding the 400 as may be too fiddly to deal with. Anyone out there pull this swap off without pain?

joe_padavano

This is about the easiest trans swap there is. The TH350 bolts into place. Your old driveshaft works, the crossmember stays in the same place, and there's no need to change e-brake cables.

The only small issues are the kickdown cable and the shifter. Get a cable and carb bracket from a 1970s Olds and this should be no problem, other than you'll need to add something to the carb throttle arm to attach the cable to. Otherwise, get an aftermarket cable.

Your two speed shifter will bolt up and allow access to all gears except manually selected low. Sometimes there's enough slop in the linkage to get into low, sometimes not. If you have a factory floor shifter, Shiftworks sells a kit to convert the two speed shifter to a three speed shifter.

White_Knuckles

Thanks JP, you hit all the points I posed. It now sounds easy to pull off. I want to keep the column shift if possible.

I'm really surprised how it just drops in. That's crazy, I never have luck with these deals.

joe_padavano

In that case, you'll need to look for a TH400 column from a 67/68 Cutlass (or other A-body). The shift quadrant inside the column is not reproduced, however if you feel adventurous you can disassemble the column and hand-grind the notches in the quadrant to allow access to all three gears.

White_Knuckles

Sorry Joe, I meant by "keep the column shift" that I'm pretty sure I'll be fine with the existing 2-speed shifter. I imagined a floor shifter like a B&M Megashifter and having to replace the column to a manual style. I dislike the pull the column shifter pin out and let the lever mount hang down approach. The thing is just a fun driver but having the floor space is nice. Stand alone floor shifters look kind of out place when your interior is cool, old-school. Now if I had buckets and a stock console? Yeah, ka-ching!! $$

You provided some great tricks on getting a proper column shifter. I'll forget that floor shifter non-sense. The cluster (gear selection) window may be an issue but I'm guessing the pointer index will simply move to the right and not hit something when attempting to shift into Low?

joe_padavano

Correct.