S/ST - 3.89 vs 4.10

[DailyDriverSst]

I am switching from a Chrysler 8.75 to a Ford 9 over winter. Just can't get 8.75 stuff anymore.

Right now I have a 4.10 gear and go through the traps at 6,000 RPM. I am debating ordering the new axle with a 3.89 gearset instead of 4.10 . Have a 1.98 low in the powerglide.

How much can I expect my short numbers and ratios to change, if at all?

Converter stalls to 4,000 RPM and it's a factory frame rail truck with full interior.

TIA

[GTX JOHN]

Not a bunch
Couple hun short times

[Charlie Yannetti]

Not sure of your engine combo, but 6000 sounds low to me.. it does depend on the power though.. I might be looking to go up, instead of down..

[Lenny5160]

Originally Posted by Charlie Yannetti

Not sure of your engine combo, but 6000 sounds low to me.. it does depend on the power though.. I might be looking to go up, instead of down..

I agree that 6000 RPM sounds like the low range of acceptable converter stall numbers rather than an excessive trap number, but I suspect the “DailyDriver” part of the OP’s handle has something to do with this.

[DailyDriverSst]

Originally Posted by Lenny5160

I agree that 6000 RPM sounds like the low range of acceptable converter stall numbers rather than an excessive trap number, but I suspect the “DailyDriver” part of the OP’s handle has something to do with this.

You would be correct. This is also a factory casting 2-bolt block that I'm almost asking too much of. Don't really want to hang the rods out of it, and I put 2-3,000 miles a year on it between taking it to work, joy rides, Rocky Mountain Race Week, etc.