installed the tach just wondering if there is any way to get them exact or do u just have to do it by ear. i think i have it close if i punch it, it will rev and then flatten out around 3200. that sound right.

 

Optical tach. Know anybody who is into RC planes/helicopters?

 

is there a harbor freight near you?
i got an optical tach from there

 

If you want to get it close, a somewhat accurate way is to find an rpm calculator. Most place's that sell tires for 4x4's will have them on there web site, http://www.4wheelparts.com/aux_incl/gear_ratio.html does. All you need to know is your tire size and rear axle gear ratio. I just installed the same tach, and used this method to get it close enough for now.

 

i dont know anybody with an optical tach heck i dont even know what one is but there is a harbor freight near me. i dont think my spedo is right since the dana 80 swap i think its about 5 off. at 65 i have it dialed to 1700 or so does that sound about right for 235 75 16s and 3.55s

 

If your speedo don't work then it's a little harder to figure out. 235x75x16 is roughly 30x9x16 according to http://www.redrock4x4.com/tech/tire_...&method=metric.
With that tire size according to the chart at 4 wheel parts you should be at 2584rpm. You can also find optical tach's on ebay for dirt cheap.

 

2500 yikes there goes the mileage

 

2500 in 4th with 3.55's and stock tires is right around 60 or so. Not sure what it should be in O/D.

 

4th is overdrive

 

2586 x .69 = 1786

 

ah yeah i might be pretty close then

 

http://www.harborfreight.com/cpi/cta...emnumber=41727
that is what i have, got it on sale for $20

 

thanks man

 

Sorry stacked, I just saw that your first gen has an auto, that makes the method I was referring pretty inaccurate due to the torque converter slipping.

 

yeah u had me scratching my head for a second