RMP and speeds in a stock M1009

[QuickSilver]

I took the M1009 down the interstate yesterday and cruised along at 75 MPH no problemo. It had no problem bottoming out the speedo (85), though I only did this for a second just to get a feel for things. Having no tach, I don't want to push the engine past the "safe" range. With the 3.08 gearing, I'm guessing 75 is ok, but I just wanted to get some feedback on that. It seemed to cruise like a dream at that speed though. My rig is bone stock, with factory gearing and 31x10.5 tires.

 

[344lbsofgetdown]

i keep mine at 65 on the speedo that means i am doing 55 speedo is off and m1009 is all stock

 

[cmroles]

I took the M1009 down the interstate yesterday and cruised along at 75 MPH no problemo. It had no problem bottoming out the speedo (85), though I only did this for a second just to get a feel for things. Having no tach, I don't want to push the engine past the "safe" range. With the 3.08 gearing, I'm guessing 75 is ok, but I just wanted to get some feedback on that. It seemed to cruise like a dream at that speed though. My rig is bone stock, with factory gearing and 31x10.5 tires.

Bone stock M1009 (3.08 gears / 31" tires / 3600 RPM Redline):

55 MPH - 1940 RPM
65 MPH - 2293 RPM
75 MPH - 2645 RPM

I wouldn't recommend more than about 65 MPH if you are looking for engine longevity.

The "sweet spot" for the 6.2L is about 1900 RPM (about 55MPH in a stock M1009). 2645 RPM is 74% of engine redline. This would be like driving your Chevy Silverado down the highway at a continuous 4400 RPM.

My M1009 drives fine at 65 MPH, but 75 just sounds way too high.

 

[Barrman]

Measure your tires too. They are probably closer to 29"-30" than the 31" printed on the sidewall.

This is a great site to plug numbers into:

Randy's Ring & Pinion. RPM Calculator.

They even have an app for smart phones. Last month I was following Kwai in my 1009 while he was trying to make a speed run in his F250 for a 200 mile dash down I-10. I have 33x12.50 BFG tires on it and had started out the drive thinking I would cruise along at 60 mph. Make a 500 mile mpg run. Kwai had other ideas and took off once we got to the interstate. I figured I would keep up for a while. 72-74 was the speed we were running. I pulled out my phone, had Colton punch in the numbers. Once it came back we were still below 2450 rpm with the actual 32" tall tires, I let it run. 16.2 mpg for that part of the trip too.

Great tool to have while going down the road with no tach.

 

[kentuckycucv]

I burry my speedo all the time past 85... she like it.

 

[91W350]

I agree with the above, 65 is about tops if you like your 6.2. If you consider it a throw away engine and junk like a lot of guys do, then 75 or 85 is right down your alley. I usually run indicating 65, both of mine are off to actual speed, actual speed is around 58. Good enough for me, oddly though, the odometers seem to be right on the money. Glen

 

[Gottlos]

It takes a while but I usually run along at about 70 mph. Stock engine, trans, diffs, but I'm running 33" tires. Of coarse I hit one grade and it's a much slower story.

 

[Barrman]

Glen,
I found the odometer and the speedometer being off different ratios odd too. My speedo is 12% slow while my odometer is 6% slow. When I had the stock tires, the odomoter was off no more than 2/10's after 100 miles compared to gps distance for the trip. Yet, the speedo was about 6% off.