Rpms 2.7 at 70mph

I just went from 3:58 to 4:56 gears in my 2.7 reg cab, 5 speed. I know the engine is turning a lot higher than before. Just curious what's the normal range at freeway speeds? I have a base model without tach so I can't compare before and after. I may put an aftermarket tach in if I can find something that looks decent. Thanks.

 

Off the top of my head, on a dry sunny day, with 31 inch tires my scangauge 2 says around 3000 Rpm

 

Ok, thanks. I not used to hearing the engine run that high so just seeing what the "normal" range is. I gotta get a tach.

 

being 96 you'll have to find a cable driven one

 

Well hell, ok thanks.

 

I have the stock 265 70R16 tires. RPMs at 70mph are about 2800.

Or you can get a cheaper $10 inductive tachometer that you ought to be able to run off a spark plug wire

 

@Mulepadre

Nice!.. I learned the hard way not to splice into the ignitor wires for tach signal..

I like the scangauge because it plugs into the OBD port. Easy cheezy.. Not really my prefered way of looking at engine RPM, but it works.

 

Ak, can you elaborate? An induction reader does not need to splice just be strapped.

What all info does the OBDII Reader for the 1996 give?

I have the ScanGaugeII on my 2003.

 

I wished I had found a inductive pickup tach I tried the regular type of tach that needs a signal and I tapped off an ignitor wire that I used for the signal.. Yeah, the ignitor didn't like that.. So I went with the scangauge..

The scangauge on my 96 give all the info if the sensor is there, TPS, RPM, Voltage, Load.. alot more info that I need.

 

31" tires and 4.30 gears turns my 5 speed 2.7 at 2700-2750 at 70moh.

 

RPM = (MPH X Gear Ratio X 336) / Tire Diameter.

Edit- as an example:

Assuming a 1:1 5th gear ratio and 31" tires (which actually have an OD of 30.5, typically) you'd be turning 3516 RPMs at 70.

(70MPH X 4.56 Gear Ratio X 336) / 30.5" tire OD =3516 RPM.

If you've got an OD transmission, say .85:1, you simply multiply the final result by .85

(70MPH X 4.56 Gear Ratio X 336) / 30.5" tire OD =3516RPM x .85 = 2988RPM.

 

Awesome...thanks. I got 265/75/16 which is I believe 31.5"

 

31.65, typically.

So for you it'd be 3388RPM, if your 5th gear is 1:1. For practical purposes (tire wear, pressure, etc) between 3300-3400.

 

Thanks. I wanted to make sure it was in a range that wouldn't hurt the engine if I was on the interstate for a few hours at that rate. I'm guessing that would be fine? Never heard it steady at that high before with 3:58 gears.

 

Right, with 3.58's you'd have been turning 2600-2700 at 70.

It won't hurt your engine, but it's basically like you're driving everywhere in 4th instead of 5th, so don't be surprised if your fuel economy suffers a bit.

 

You can tap the green tachometer wire right behind the cluster. I don't have any pics readily available but I ran an Autogauge tach in my truck for years like that. Since I didn't have a clock either I used the clock wires for power and the gauge light trigger.

 

Sounds good. Thanks for the info!

Thanks, I'll have to look into that.

 

I was running this tach because it matches the factory cluster pretty well for an aftermarket gauge:

$64 AUTO METER 2306 Autogage Mini Tachometer,2.750 in., Black dial/Black bezel

https://www.amazon.com/dp/B0009SS6GS/ref=psdc_15716751_t1_B0009SQL2E

mine is up for sale if you're interested

 

Why run 70 and not 65 if possible?
At 65 my rpms are a smooth 2500, its kind of a sweet spot for my motor's vibration.

Believe it or not, maintaining that sweet spot is more important to me than going fast.
So I take my time enjoy my ride, while everybody passes me by on city freeways.

 

I may do that. I always at least maintain the speed limit. I don't get on the freeway much but st least want to maintain 70. I'll try it and 65 and see how it goes.