2nd Gen Non-Engine/Transmission Top speed vs RPM

[Gary - K7GLD]

Recent posts concerning a test utility for the instrument panel have indicated that with the tach at 4000 RPM, the MPH is at 120 MPH...



BUT some time back, guys were comparing their top speed capability with these trucks, and several commented they were capable of getting about 130 MPH outta their trucks - is that possible, and at what engine RPM?



OR, am I losing even MORE of my diminishing mind? ( I think every time I lose more hair, the roots bring a bit of grey matter with them... )

 

[Turbo Tim 1]

I have 4. 10's and considering I'm at 2200 rpm at 73 mph plus or minus and the redline of my truck is 3400 rpm that equates to a max possible speed of 112 mph with my truck

 

[Snow man]

my truck runs 118 max with 285 tires,and an auto trans at 3500RPM. The speedo shows 114, the tires size makes it up,the dynojet says 118mph. So the same truck with 3. 54 would easily go faster than 130mph.

 

[JJW_ND]

On a Dyno ...not the road!

Mine did 139 mph with 235\85R16 tires, 3. 54 rear gears, in 5th at 4K rpms.



I had just added the 4K GSKs and wanted to see what it sounded lilke at 4K RPMS high gear.



MPH was on the dyno, I would not run this speed on the road.



The previous year, same dyno, Verlyn Fast (Of Fast Coolers) ran his 2002 6sp, 3:54 gears, 265\75R16 tires and a Overdrive up to 155 mph (speed limiter wire cut) His was at 3400 rpms in 6th Over. Ten ply LT tires really don't look well at speeds over 120.



jjw

ND

 

[WestTN]

I think the test function just allows a technician to see that each gauge goes full range. That would make sense for a gauge test even though 120 mph at 4000 rpm's does not.

 

[Gary - K7GLD]

I think you're right Dennis...



My truck is turning 2000 RPM at 70 MPH - so a rough estimate would give 140 MPH at 4000 RPM...

 

[drawson]

My truck on a couple of differant dynos did 143+ in 5th w/255/85R16 tires

 

[Chipstien]

It is alot harder to do 140+ with 140 mph winds too. It is easy to go fast on a dyno, much harder when you are fighting the wind too. That being said, I know that I have done over 120 on the freeway with the 4. 10's and 315 tires. Funny thing is, these trucks handle fairly good at that speed as long as there are no turns.

 

[Gary - K7GLD]

I've read of defueling at the upper RPM ranges - where does that take place, and does it totally limit the RPM, or just greatly reduce power for engine safety?

 

[Woodenhead]

What are you guys using for tires at these speeds. I've recently found my BFG ATs have a separation starting at a radial spice on one tire and the only cause I can think of is a couple of 110+mph runs in the road.



Mike

 

[Chipstien]

Originally posted by Gary - KJ6Q

I've read of defueling at the upper RPM ranges - where does that take place, and does it totally limit the RPM, or just greatly reduce power for engine safety?

Yes, they start to de-fuel at 2700. However Gary, if you upgrade that Comp to the drag version you won't have to worry about that anymore. The Drag -Comp compensates by adding more fuel to make up for it. Makes the Cummins strong all the way to 3400 rpm's Just think how much faster you could pull the RV.

 

[Gary - K7GLD]

"What are you guys using for tires at these speeds. I've recently found my BFG ATs have a separation starting at a radial spice on one tire and the only cause I can think of is a couple of 110+mph runs in the road. "



*I* certainly wouldn't advise running at much above 100 mph - and THAT only for a short burst - as you say, these tires are simply not rated for that sort of speed. My question was more related to capability with available engine RPM and common sized wheel/tire combos. I've had mine up around 110 once for a very short burst, still accellerating as tho' no end in sight - but *I* was finished!



Used to be that Ford and GM diesels were governed to about 95 mph - dunno if that is still true or not.

 

[Froadin]

3,200 rpm, 112 mph, 3. 55 gears, 265/75 16 tires. Held this speed for about a mile or so. It felt very smooth, and it never really felt like the motor slowed down any (still would accelerate if I let it).

 

[Mundgyver]

131 mph can be done. I have been there once with a small Mercedes Kompressor behind me on an up-hill run in Washington. I tac'd out at 3200 if the tach was correct. Speed was recorded on my GPS. I have 285's on the rims. See my sig for the other mods. The truck felt ok, but I would have liked to see a pic of the tires and what they looked like. I have gotten away with this once, I don't think I will try a second time.

 

[SuncoastCustoms]

Top speed so far, keyword "so far," is currently 125mph. Truck was handling smooth with 245/75 tires. I need higher speed rated tires, lol. All this was at around 3200-3400rpm, didnt really wanna look down.

 

[dlange]

travisG ran 142 on a dynojet.

 

[Mundgyver]

If I am not mistaken, did not the banks side winder project claim the speed record of 214 or there abouts. I know it was a 5. 9 cummins with an NVG 5600 6 speed gear box that had been balanced out. I do not recall what the tach numbers were. Seems like it was in the 4,000 range though. And I am thinking he had a double overdrive. Anybody know about this

 

[Gary - K7GLD]

Among other things, I seem to recall the Sidewinder used both an aftermarket OD and very high-speed differential gearing - I also seem to recall some problem with the ring/pinion gear during the runs - but may be thinking of another truck - it's been a while, and my grey matter is developing holes...

 

[johncameron]

Actually the Sidewinder ran 222MPH on the ground with a stock NV5600 (no double overdrive) with something like a 1. 87 rear-end!

 

[slo-ryde]

I came real close to pegging the speedometer on a lonely highway in the Nevada desert. It's unreal to have 3 tons of stock truck going that fast!