99 shorty

[89obsSB]

On the Denali cluster, the speedo is 120 MPH, the gauge needles are white until you out on the lights, then they turn yellow. And the background nbers turn a bluish green color when you turn on the lights. The OE cluster is only 100 MPH, the needles are yellow always, and the background green when the lights are on. I do push my truck over 100 MPH from time to time, so for me, that was the main reason I wanted a Denali cluster.

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oh ok I see.

 

[kennythewelder]

How tall are the tires? We'll figure it out right now!

275/60/15 with 342 gears, ànd the OE 4L60E. The only thing about the calculator, does it count for wind resistance?

 

[stutaeng]

275/60/15 with 342 gears, ànd the OE 4L60E. The only thing about the calculator, does it count for wind resistance?

Negative on wind resistance. The torque converter is locked, right? The calculators are just based on the geartrain rations multiplied together and the size of your tires...

 

[yevgenievich]

Negative on wind resistance. The torque converter is locked, right? The calculators are just based on the geartrain rations multiplied together and the size of your tires...

Does the stock ecm program lock up torque converter at wot?

 

[Frank Enstein]

Well, before I rebuilt the rear end, and still had the OE 342s I pushed it to 5200 RPMs in OD. This was long before I did the Denali cluster swap. I figure I was doing about 140ish MPH or so. Now that I have 373s it may do that fast, but I would be at 5500 RPMs or more. It pulled good to 5200, no problems, and the power never faded. Just a good straight pull all the way to 5200. I was on a very long free way in the middle of no where. At that time, GPSing the speed never crossed my mind. Now I wish I had. With the rear end rebuild, I gained 300 RPMs at speed. So now at 77 MPH, I am turning 2700 RPMs. Before I was at 2400 at 77 MPH. The 373s do pull better, and I love the Eaton trutrack.

Works out to 127 mph in drive and 181 mph in OD!

 

[Frank Enstein]

165 mph in OD @5200 rpm.

I know the factory tach's aren't super accurate and the same with the speedometers. The error doesn't add up to much at 60 but they become more and more apparent the faster you go!

The formula is cute, but it doesn't factor in tire growth or slippage. The faster you go the farther off it can become!

Notice a pattern here?

It is very useful to choose axle/transmission ratios!

 

[kennythewelder]

Works out to 127 mph in drive and 181 mph in OD!

Yeah, I was in OD. 181 just doesn't sound rite. I know the torque converter was locked, and I know it took a good while to come off the 100 MPH mark once I was at 5200 RPMs. I am 100 percent sure what I read on the tach. It was 5200 RPM in OD. I rember it well. The rig mechanic had a new Denali 1500 with a 6.2 L in it. I knew it would be limited to some where just over 100 MPH. So He was messing with me to that point, but I just floored it, and keep my foot there. My truck just keep pulling. When I got over 5000 RPMs I couldn't even see that Denial in my rear view mirror any more, so I thought just how much more should I push this old truck. When it hit 5200, it was still pulling good, but I just figured that was fast enough. I have been 140 MPH in my 1973 Challenger may times. It felt like about the same speed. That is why I made the comment about wind Resistance. A 140 MPH wind force pushing in the opposite direction of travel will drive up the strain on the engine, driving the RPMs up. I would be willing to bet that who ever figured this RPM to MPH VS tire size, and gear ratio, didn't factor in wind resistance. The wind drag coefficient ratio will be a lot higher in my pick up truck, than it will be say, in a Testla for example. It will take more force to push my truck down the road, than it will a Testla. This will relate to a larger force to move my truck, and that will relate in more RPMs. The wind drag coefficient ratio is much lower at say 40 MPH, than it will be at 140 MPH. I used a calculator like the one you used, when I first did 5200 RPMs in OD, and I remember it was around 180 MPH. But I don't think that would be rite without calculating wind drag coefficient ratio, but hey what do I know. Like I said, at that time, it was a spur of the moment thing and I didn't have a GPS to clock my speed.

 

[Frank Enstein]

Unless the trans was modified, it won't allow a 3-4 upshift at full throttle. So locked convertor, third gear would be 130ish mph.

That's still kinda zoomie for a pick up truck!

 

[kennythewelder]

Unless the trans was modified, it won't allow a 3-4 upshift at full throttle. So locked convertor, third gear would be 130ish mph.

That's still kinda zoomie for a pick up truck!

No, I was in OD. It was the stock OE trans. A 4L60E. As for it not allowing a 3-4 up shift, again No that's wrong too. I have done it to many times, both before I had the trans rebuilt, and after. You can count the shifts. It comes out of 3ed and shifts into 4th or OD at WOT. Always has. Keep in mind, this with out pulling anything, or having anything in the bed. Believe me or not, that is your choice. I know what happened, I was there. I know how the trans shifts and did shift before I had it rebuilt. I have had the truck for almost 20 years. One of the issues I had with the rebuild was that the trans would not shift into 4th at WOT. It would rev, then try to shift, then rev again. It took it back to the trans shop who built it for me. They hooked up a hand held computer to the trans , and made it shift. It was the VSS that was bad. They even agreed it was an issue, and that the trans should have been shifting at around 70 to 80ish MPH out of 3ed into 4th. Even a stock trans should do that. This is a shop that has been building transmissions for over 40 years.

 

[yevgenievich]

Before making it much quieter, took a short idle video.

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