4032 RPM at 60 mph with 30 inch tires requires a 6:1 axle ratio.

If you are in low range (1.96?) with 30 inch tires and 3.50 axles, you will turn 4610 RPM at 60 mph.

 

That would be a 7.14 ratio if he's turning 4k at 55, it not unheard of for tachs to read normal at idle and show rpms way higher than what the engine is actually turning.

 

Alright guys don't give me to hard of a time. I took the casing off of my Tach and there was a little switch there on the number 6, haha. I'm guessing now that it's on 8 it will probably read around the right rpms. I didn't know the switch was on the inside of the TACH.

 

No reason to feel bad about it, you aren't the first or last person to find out about the switch so I doubt anyone will give you a hard time..

 

NO SOUP FOR YOU!!


Glad you got that solved. Glad we could help.

 

We've all had it happen. Lol.

 

What does it read now?

 

With 33s and 3.50 gears in 4th gear 2,000rpm will be about 50mph. I ran this truck for years with no speedo and had 33s.1,500 rpm was about 40 and 1,000rpm was like 27mph.

The same truck with 4.10s and 33s 3,000 was roughly 60. 2,000rpm was about 40mph

Same truck still with 4.10s and 37s. 2,200rpm was 60mph.

This was all by factory tach and using those radar signs on the side of the road, all in 4th gear on a NP435 so 1:1.