7.5 ring 27 spline pinion GM Differential

I have an opportunity to pick one of these up. My situation is I do not know what spline axle I have without breaking apart. There are two choices one with a 28 spline axel and one with a 26. What were the years of use on these two choices so I can better pin down my purchase.

Part two:
can anyone fgive me an indication on stall speed. here are the stats

Chevy 350 / 300 horse, Turbo 350 / rear gears 2.73 = what stall?
Chevy 350 / 300 horse, Turbo 350 / rear gears 3.42 = what stall?
Thanks for the help.

 

the year break is 1988. The books list up to 1988 as 26 spline and 1988 to present as 28. Hope its 88 and newer.

As far as stall speed... there is a lot more involved. Vehicle weight... tire size... etc to get the best converter. Intake rpm range and carb is another. I would say, judging by the 300hp mark... that 1800 would work fine in a lighter car. If its a heavy beast, you might want to jump to a 2000-2200.

Mike

 

Jegs offers a 2000-2300 for $99.
The car is 2000 lbs.
Tires are 29" in rear
Carb is Demon 650
What is the difference between a variable fixed trans and a fixed pitch? they offer a 2300 to 2700 stall for $129 but say that the trans in use must be fixed pitch? What do they mean? Is the idea to keep stall speed below highway RPM?

 

The stall speed mostly depends on the cam, bigger cams need a higher stall speed. Also the gears you want to run depend on the cam....bigger cams need more gear. The 300 horse cam is pretty mild, you could use a stock stall speed converter, or maybe go up to 2000-2200 Also stall speed for any given converter will depend on engine's torque output, vehicle weight, etc.

Variable stall converters are a TH400 thing...and then only on a very few TH400s...don't worry about it.

You probably want gears right in between your two choices, for the setup you have. 2.76 would be great on the highway but sluggish at low speeds, 3.42 would be great around town and ok on the highway, neither ratio will be optimum for both.

 

Hydramatic made a bunch of 400 transmissions with "switch-pitch" converters but never a 350 trans. The switch-pitch was electrically switched and the converter could shift from a "loose" vane setting to a tight vane setting, it wasn't really variable, it was one setting or the other. All other converters are fixed unless they might be referring to a lock-up converter which uses a mechanical clutch to lockup the converter (no slip) when commanded.