Transfer case speedometer gears

[Jorge6.5]

I just swaped in an np241 t case in my truck, the truck has 4:10 gears and the t case came from a suburban with I think 3.42 gears.

Now my speedometer is not accurate, hard shifts not until 2500+ rpm

Already checked the speed sensor and put in a known working one also checked all wires and connections and everything looks good.

I took out an np243 and swapped in a np241, I'm thinking the speedometer gears in the tail housing are different resulting in my issues. Suggestions please

 

[THEFERMANATOR]

Theres no gears in the transfer case, just a 40 tooth tone wheel that the speed sensor reads. There is a chance that if teh transfer case came from a manual truck it could have a 17 tooth which would put the speedo WAY off. Also make sure you're using the correct speed sensor. Also make sure that it isn't triggering the 4 low wire to the ECM as that will throw the shifts WAY off.

 

[Jorge6.5]

Thanks therm, the cases are both from an automatic. I tried the speed sensor from the np243 in the np241 and made no change. How will I know if it thinks its in 4low? Will a scanner tell me that? Maybe the 3 wire transfer case switch is bad, later I will swap them out from my np243 case and see what that does

 

[jrsavoie]

I'm guessing that it has something to do with switching from a push button to a floor shifter.

Wires will not be used and left hanging. And we know how critical wiring is on these vehicles.

Did you have auto-track? - The 4 button, push button 4 wheel drive?

I'm closely following this, as I have considered the same swap.

What happens with the wires to and from the push button?

 

[Jorge6.5]

I switched the selector switch sensor on the t case and no change, Its going to the mechanic on tuesday lol