I have a 51 Chevy Fleetine. It currently has a 235 with the 3 on the tree tranny. Would a powerglide be a direct swap? How would the linkages work compared to the 3 speed?

If your talking about the later 70's model transmision the answer would be no unless you go with some type of adapter, plus the later model would also require a different rear axle. There was an earlier version in these cars that would bolt up, they also had a different set of gears (taller). As for linkage, there is noway the 3spd linkage would work, your only coarse here is to swap out the column or using a floor shifter.

It would be the same year 1951 powerglide. can I keep the same driveshaft and rear end? Is it easy to install a floor shifter?

A '51 'glide will bolt up and you can keep your current rearend, but it will be a 4:11. The 50-54 'glide cars used a 3:55 rearend. You can use the column shifter from a 49-54 car, or you can use an aftermarket floor shifter of your choice.
I'm not positive, but there may be a difference in the 'K" member between stick and glide? unless someone else can confirm this, I would make some measurements just to be sure.

Alright, so is a 4:11 or a 3:55 geared higher? Would you know what the top speed would be with a 4:11?

4:11 would be a higher ratio.
3:55 would be a higher speed.

you will go faster per a given rpm with the 3:55 rearend.

top speed would be dependent on the abilities of the engine.

There are gear calculators on alot of websites that will allow you to plug in different combinations to see what rpms you would be turning. Randy's ring and pinion is one that comes to mind.


How about some background info. What exactly is it that you are trying to accomplish?