I have a 99 Toyota 4 Runner. It has the V6 3.4 liter engine. It appears that my tachometer is off. Can someone tell me what the tach should read when driving at 70 mph? Mine is reading 3500 rpm. This seems high. How do I determine if it is the tach or is the transmission not shifting into high gear. I do notice if I click the overdrive button off the tach will show an increase in rpm. Tks
"Satmechanic" found these unused words:
Rear end ratio would have to be known, different units will have other RPM.
Engine speed while driving is a function of trie size and axle ratio. The transmission ratio plays a role as well, but the tires are likely to be smaller than they ought to be, or the gear ratios are likely to have been changed before the transmission would be altered.
Having said that, you notice that the engine speed increases when you de-select overdrive. This action is the same as downshifting from a high gear to a lower one, and the result is an increase in engine speed.
Odds favor the tachometer being accurate. Any mechanic should have an inductive-type tachometer that clamps a lead on a spark plug wire and displays the number of times the spark plug fires, compare this number with the tachometer in your truck.
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