Safe speed

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Jul 2, 2013 | 11:28 PM

#16

85e150

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265/75x16s are nominally 32".

32" tire, 1:1 high, 4.10 gears, 95 mph = 4090 RPM

With 4.56 gears, 4549 RPM

With 4.88 gears, 4867 RPM

32" tire, 1:1 high, 4.10 gears, 5500 rpms = 128 MPH.

The only factors here in question would be tire diameter, as we are going off a calculator, not actually measuring them, and actual input RPM, as we can't measure torque converter slip on the C6. The rest of it is pure math, and is the same regardless of brand etc. It is possible to get some tire slip at high speeds, but you would be in serious trouble and might not live to tell the tale if the back end were floating that bad at that speed.....

Tachs and speedos have been known to fib a little.

Jul 3, 2013 | 12:04 AM

#17

twigsV10

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From: Iowa

It was very likely the torque converter slipping, it had to rev up to 1100-1200 rpm just to move. Running it out of oil numerous times probably didn't help, trans starts slipping add oil engine loses oil psi add oil but the thing that finally killed it was getting hot and adding antifreeze that was going in the oil.....

My brother-in-law is full of BS so I shouldn't quote him.

Jul 3, 2013 | 12:21 AM

#18

twigsV10

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From: Iowa

What I was getting at was if a 460 can that sort of torcher the 390 should be ok at several thousand rpms less, with better maintenance hopefully. LOL

Jul 3, 2013 | 10:16 PM

#19

Boodrow379

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Joined: Jan 2013

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From: New Mexico

Quote:

Originally Posted by Boodrow379

I have a 390 with new process 435 with 4.10's. No rpm gage, its screaming by 50 but ive ran it at 60 a couple times for about 10 miles. Do you guys like number dummy think that is ok and it wont hurt the motor? It doesnt overheat at all.

I'm talking about a stock 4 speed here, you guys really think i could go 95 if i wanted to? Just making sure, lol ive been afraid to go over 60

Jul 4, 2013 | 12:17 AM

#20

85e150

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If your engine will hold together against WOT till you hit 4090 RPM, you can go 95 MPH.

Along with your tires, don't forget your tires..... Old, checked, repaired, recapped--best stay at 50 MPH.

95 MPH usually brings a felony arrest and reckless driving charge, so think about this carefully before you head out.

But we are off topic here, as you asked about a "safe speed". 95 is not a safe speed for your vehicle.

Jul 4, 2013 | 08:17 AM

#21

Dave145

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Joined: Nov 2011

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From: Burlington, WI

I wouldn't do anything over 70. I've done a speed run and gotten to 100...lets just say ill NEVER DO THAT AGAIN! The truck started shaking and my Rpms were up into the mid 4000s. I've got 30" tires, a three speed auto trans, and 4.50 gears in the back of my camper special.

Just because a speedometer says a car can do 85+ MPH, doesn't really mean the car can/should do it

Jul 4, 2013 | 09:51 AM

#22

gfw1985

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Joined: Mar 2008

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From: Raphine, Virginia

grimmjeeper.com is a handy calculator for figuring gear ratio's, rpm's for any given drivetrain combination.

Jul 4, 2013 | 09:58 AM

#23