65 chevy impala SS

i have a 65 impala when im driving it feels like it needs another gear on the tranny i already changed it i installed a th350 it still does it could it be my differential?

I also always had the feeling that every TH350 I owned needed a overdrive gear. I conclude you moved from a Powerglide to a TH350?

You can’t get out of you Accord or Camry or current model Malibu and not feel you are getting in a truck when you get in your 65 Impala.

yeah i got away from the power glide ive been told to install a 700r4 ? have you ever heard of that.

High gear is direct drive, i.e., engine speed in equals drive shaft speed out. Replccing a 2 speed with a 3 speed only added an intermediate ratio. A 700R4 will add an overdrive 4th gear and slow the engine noticeably. Final drive on the non SS models of that period often had final drives in the low 3.00 range. Some were geared so high that they could remain in passing gear (low range) in excess of 70 mph. I vaguely recall a 59 with a 409 that would hold passing gear to nearly 100 mph. Gasoline was 19.9c back then, BTW.

Both the powerglide and the TH350 have a direct high gear i.e. the drive shaft turns almost once for every revolution of the crankshaft. I say “almost” because there is torque converter slippage to account for unless a locking TC has been adapted.

The TH 700R4 is an option as it is a 4 speed automatic and the fourth speed is an overdrive. Do check the rear end ratio because it may be high due to the powerglide and possible smaller engine. Going to a higher ratio, i.e. closer to 3.00 or less, is also an option but the car will accelerate a little more slowly. Check through past issues of Hot Rod magazine as I bet this issue has been raised in the “Ask the Experts” section.

Hope this helps.

thanks that makes sense so there no threat to my engine ?

Shouldn’t be, I went from something like a 3.23 to a 2.73 on a 6 cyl. Duster, just slowed my acceleration (not that there was much to begin with). A lot easier to change the rear axle than the transmission.

What ratio do you have right now?

With a TH350 and if one assumes the gear ratio is a 3.23 or 3:42 this means the engine will be turning about 3000 RPM or better at 60 MPH; give or take some each way.
Everyone is accustomed to Overdrive transmissions so when getting behind the wheel of something without an OD the engine sounds like it’s screaming.

I’ve got a Chevy here (has TH350) and it also had 3:42 gears. I swapped the rear axle out with one that had 2.56 ratio and it really brought the RPMs down. At 60 it turns about 2400ish or so. It still pulls pretty decent off the line in spite of that gear ratio.

A 700R4 would be the way to go. The early ones were a bit problematic so a rebuilt one or a trans from late '88 and up would be best.