I just installed an aftermarket Tach on my truck, but im a little skeptical about what its reading. So I was wondering if this sounds accurate-

2300 @ 70mph in 5th
1600 @ 30 in 3rd
and it says im idling around 600

My guess is that its off by a few hundred rpms somehow, because the truck sounds fine at idle, and at speed, when i hear the motor it doenst sound accurate to the tach.

BTW it has 3.56 gears, and 225/75/15 tires. Thanks for any input <img src="/forums/images/graemlins/cheers.gif" alt="" />

I've got an automatic w/4.10 gears, but 265/70-16 (~31")tires, and my truck turns about 2100rpm at 70mph, and idles (fully hot) at around 600-650 with the A/C off.

You've got taller gears, but smaller tires. I couldn't find the specs on the differences between the 5th gear ratio in your tranny and the O/D ratio in my automatic, but the rear-end gears versus tire size should make your driveshaft turn about 6% slower than mine at the same road speed. Again, the top gear ratio differences between the tranmissions could change your actual difference in crankshaft speed up or down from this 6%.

Another possible difference is in our speedometers -- I've checked mine with a GPS and it's pretty close. At 70, a 4mph difference in speedo's could erase the tire/gear differences above.

That said my guess is your tach is at least reasonable.

OK your engine redlines at 5750 RPM.. if u want to be daring let it hit the limiter and see where the needle stops at... then u can tell if youre off..

Good suggestion to redline my motor, but I did the next best thing. Took it off because who needs it anyways <img src="/forums/images/graemlins/smile.gif" alt="" />
I did put on 4 new 30 X 9.5 Toyo Open Country AT's and changed all gear oils to syntheic though today. What a difference in shifting and ride. Cheers for the replys though <img src="/forums/images/graemlins/cheers.gif" alt="" />

Oh yeah, i forgot to put a <img src="/forums/images/graemlins/ignore.gif" alt="" /> in my post... heh...

WHo needs a tach? They're nice to have....