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IMO they should test for top speed, at least to some speed at or above where they set the limiter. Better to find high speed instability before the vehicle goes on sale. Murphy's Law always applies.
Well, many moons ago, I tested a 1972 F100 with a built 390 quite a few times and miles well in excess of 100 MPH! A gentleman that I worked with came home one day with a ‘73 F100 that someone had dropped in a 428SCJ with a 4 speed top loader and he tested his faster than I did my ‘72! Of course, all this info is just FYI and totally irrelevant to the OP’s question.
I think that when the driveshaft fails might be the limiting factor in how fast it can go.
It's pretty exciting when one fails. I had a modified driveshaft in an engineering development F-250 fail at 65 MPH. It broke at the front and the rear of the truck pole vaulted over the broken shaft. That was enough excitement for me.
TL;DR - always make sure your driveshaft is up to the task..
Had a 1996 Thunderbird with the 4.6L and a 3.27 rear. About two years into it, I started modifying. Put a 3.73 gear in it, w/Auburn lockup. Got a tune, unlocked the limiter - I think it was 92 with the 3.73 rear.
BMW tailgating me at 70+ while I'm in traffic, as soon as it opened up I went on it. At just around 135MPH, there was a horrendous sound and vibration, backed off and it came to a calm. Drove it all the way home, never noticed any other problem, just figured the driveshaft was the problem and resolved to fix it at some point (and don't go 130+ anymore). A few months later, bring it into the dealer for some warranty work, and they call later in the day to tell me they noticed the transmission extension housing was leaking, and they ordered parts. Turns out, the bushing in the housing was all galled-out.
Moral of this story: Don't underestimate the limit of your driveshafts.
Last edited by krewat; Aug 25, 2020 at 02:51 PM.
Reason: rookee mistake
I took our F250 out today and at 2000 rpm it was doing 82 mph. So if it had enough power our truck would attain 164 mph at red line of 4000 rpm.
I will never find out.
Max speed at 4000 RPM for my truck with 3.55 and 20" wheels (34.3" OD tire) works out to 171 MPH in theory, based on gear ratios.
Interestingly, I did a back of the napkin calc of HP required to overcome air drag using coefficient of drag and frontal area figures I got from the internet. Take this with a grain of salt, but I used 35.1 ft^2 frontal area, and 0.57 Drag coefficient. These very well could be wrong.
At any rate, it would take 134 HP just to overcome wind resistance at 100 MPH, and that figure hits 400 HP just to overcome wind resistance at 145 MPH. So unless I make my truck more aerdynamic or bump the power, I aint going 170 MPH.
Max speed at 4000 RPM for my truck with 3.55 and 20" wheels (34.3" OD tire) works out to 171 MPH in theory, based on gear ratios.
Interestingly, I did a back of the napkin calc of HP required to overcome air drag using coefficient of drag and frontal area figures I got from the internet. Take this with a grain of salt, but I used 35.1 ft^2 frontal area, and 0.57 Drag coefficient. These very well could be wrong.
At any rate, it would take 134 HP just to overcome wind resistance at 100 MPH, and that figure hits 400 HP just to overcome wind resistance at 145 MPH. So unless I make my truck more aerdynamic or bump the power, I aint going 170 MPH.
And put those driveshaft safety loops on the driveshafts to protect the truck, driver and to keep it on the road. 😄
I completed my truck back in 2013. All new lift, tires, suspension and tuner. I use to drive an hour on the freeway to get to my job at that time. Now I didn't change any gear ratios, but my 40" tires helped with my speed. This is not something I've done since because it scared the chit out of me and really, how fast do I need to go in my truck? It's just what I have created for low end towing. Done a little drag racing but not in a F-350. Anyways, sometimes you get curious, at least I did, and driving early in the morning with no one around I figured I'll stomp on my big pig and see what she can do. I hit 118mph and would have easily kept going but I honestly didn't have the guts. I have an upgraded, balanced driveshaft, not that could have saved me. I will admit the truck felt tight and strong with no vibration. The sound of my tires and the way the passing lines were going by me is an experience by itself. I felt like I was in another dimension. I'm just hoping some of you sunday drivers don't call me out on this one. Only one in question here was me, by myself, alone on the road. Sometimes, we need to know things....
Reminds me of a Honda V45 motorcycle I had back in 1983. I am not a fan of two wheel vehicles, because I never was good at riding one, but I did want to know just how fast this one could go, so one day I laid down on the tank and opened it up. When I could not stand it anymore I looked up and it was 120 mph. After that, I kept it at a maximum of 65 which was the speed limit for our freeways here in Northern Calif. Most of the time I kept it off the freeways, because I did not feel safe even at highway speeds. Mostly because I was not a good rider. I sold it kept my high speed to four and three wheel vehicles. I am a licensed commercial pilot , with over 10,000 hours flight time, so that is where the three wheels comes from. The fastest I have ever been on a four wheel vehicle was our supercharged Corvette, which was geared and powered for 200 mph, but I only had it up to 185 mph. The quickest four wheel vehicle I have driven is our 1960 Falcon. By far the scariest ride I was in was a speed boat that did 99 mph on a lake. It felt like we were doing 300 mph. I never got back into that boat.
My point is, we only have one life to live, so enjoy this one, but keep safe and make good decisions with safety in mind, so you and others live your life to it's fullest.
By far the scariest ride I was in was a speed boat that did 99 mph on a lake. It felt like we were doing 300 mph. I never got back into that boat.
That reminds me of a video on youtube I recently watched of a drag boat doing a holeshot. Looks scary as hell from the video, couldn't imagine being the second seat of that thing.
My buddy owns 400 acres and has his own one mile long private road located on the property which is relatively straight. No other residence or any people are around for miles. With the same thought in mind as the original poster I just wanted to see about how fast our trucks would go with the limiter removed. At 106, it shifted into 6th, the tuner said it did 97 mph in 13.8 seconds at 1/4 mile. At under a half mile it hit 131 at 3,000 rpms and thats when the pyro hit 1450 degrees and the tuner began defueling. And this is a 2011 f350, 3.51 rear end, 4wd, crew cab, deleted, egr removed, straight pipe, s and b cold air, sinister charge air pipe and egr throttle body removed and h and s canned tunes 159,000 miles. Nothing out of the ordinary with this truck. You can say it was dumb, stupid, reckless or even why I would want to, but it's done and over with and the truck runs and shifts fine.
By the way, the amount of wind I could hear rushing past the truck and past the sun roof was extreme. That's literally all you could here. And this was a 2011, so the 2015s and up with the better injection pumps and turbos probably get there faster, easier and would go right past that. I've my pyrometer set to defuel at 1450 and I was going fast enough anyway
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