spacemanspif

iTrader: (5)

Just wanted to check to see what others' cruising engine speeds are to compare to mine.

5.3/4L80E and 3.73 gears

at 70mph my engine turns about 2800 rpm. How does this compare to others with similar setups? Since my powertrain is all junk yard parts I'd like check this info against others' to make sure it is all performing as it should.

Thanks,

Mike

00MaroonZ28

iTrader: (3)

4L80 has bigger gears. That's pretty high up there.

71403

Yup, with 3.73's and 27" tires I was right about where you are (~2700rpm)

Stepped down to 3.31 gears now it's ~2300 @ 70. 6.0 (LY6) has enough grunt didn't really notice that big of a change. Sure not enough to make it worth buzzing down the highway.

4l80e was already in the car, next swap it's 6 speed or bust.

Bo185

Considering the 4l80e only has .75 OD. But you would need at least 23'' tall tires to run that RPM. So something is wrong. IEW your speedo is off. Did you verify the speedo with a GPS?

And if one has 27'' tires RPM should be 2473 not 2700 @ 70 with a 80e.

Plug in your numbers and tire height. Then use .75 for trans ratio.
http://www.ringpinion.com/Calculators/Calc_RPM.aspx

bczee

iTrader: (12)

I have a Viper T56, 4.10:1 rear, 275x40x17 tires ... @ 65 mph = 1750 rpm. @ 70 mph, just a bit above 2000rpm....

I get 26 mpg while on the highway doing 70 - 75 mph.

BC

spacemanspif

iTrader: (5)

thanks all for the information and sorry for the lack of reply...I was on vacation.
good thinking with checking against a GPS, since my speedo is programmable there is a certain amount of human error involved in the calibration. While I am double checking my speedo I think I might also double check my tech using the scan tool, I know its correct at low speeds but haven't checked it while at highway speeds.

Thanks for the link to the calculator too, I double checked it with my tire size 225-65-15 and it says it should be right around 2500rpm. Time to start rooting down the issue

67RS/SSx2

Do you have a lock-up converter? If so, is it working? That should be worth 200 rpm.

spacemanspif

iTrader: (5)

I believe the stock 4L80E converter is a locking type and I think it does lock. If I drive in in regular "D" it shifts 2x for running in 3rd gear, and then when I shift into "OD" it will shift into 4th and then a little later will the exhaust pitch will change a little which I believe is the converter locking.

So far I have not been able to adapt the old method of lock-up testing (pressing very lightly on the brake pedal while cruising on the highway and watch the RPM jump up a little) to this trans...I figure it has to do with the computer control and maybe it just holds the converter locked for longer.

gMAG

iTrader: (1)

28" tire/3.70/OD .063...@ 60=1700. @ 65=1900. @ 70=2050. @ 75=2200.

leon phelps

my 65 impala with 4l60e and 3.31 gears is at 1950 at 70.

29" tall tires.

oldgoat69

4L60E, 3.55 gear 25.9" tire = 2400 @ 72 mph. Also have seen 23 mpg best so far.