too many rpms
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Senior User
Joined: Dec 2006
Posts: 130
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From: Panama Illinois
too many rpms
when i drive my truck with 33in tires at 60 mph the tach says 2900-3000 rpms witch would mean i had somewhere in the neighbor hood of 4.80 gears witch it doesnt it has 3.54. so who thinks that whoever had this truck before put a 6cyl tach in?
Super Moderator
Joined: Apr 2004
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Could be. Some tachs have a switch. Pull the tach, look at it, see if the back comes off, if there is a switch, etc. Then check the manufacturer's web site for info on how to calibrate for 8 vs. 6 etc.
Or, get another tach.
Calculators here, you can put in your axle, OD ratio, etc.
Novak Conversions - Gearing & Gearing Math for Jeeps
Or, get another tach.
Calculators here, you can put in your axle, OD ratio, etc.
Novak Conversions - Gearing & Gearing Math for Jeeps
Postmaster
Joined: Feb 2008
Posts: 2,658
Likes: 5
From: Out of here
With 4.10 gears that is exactly right.
My truck has 4.10's and 33's and I turn 3000 rpm @ 65 mph. Time for a 5 speed me thinks. I actually get better mpg in the city because of the lower speed and rpm's.
BTW, you are actually going much faster than you think. You need to go up 1-2 teeth on the speedo gear to fix it.
My truck has 4.10's and 33's and I turn 3000 rpm @ 65 mph. Time for a 5 speed me thinks. I actually get better mpg in the city because of the lower speed and rpm's.
BTW, you are actually going much faster than you think. You need to go up 1-2 teeth on the speedo gear to fix it.
Post Fiend
Joined: Jul 2004
Posts: 8,786
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From: Northern California
The 6000-RPM Factory tach was used in both 8 and 6 cylinder trucks.
When used with a V8 there is an extra ground hooked to the "8" terminal of the tach through the cluster printed circut.
On 6 cylinders this "8" terminal ground is left ungrounded.
When used with a V8 there is an extra ground hooked to the "8" terminal of the tach through the cluster printed circut.
On 6 cylinders this "8" terminal ground is left ungrounded.
