What is the top speed I can hit in my Denali with stock 3.73 gears and my 4L80? I have enough power to max it out, I just haven't taken it higher than the 130 range.

 

Does it have the stock driveshaft in it? If so, I wouldn't even go that fast with it!

 

In overdrive with a 31" tire, spinning the engine to 6700 would get you 220mph. So you dont have the power to push it that fast.

In 3rd 165 would be about 6700rpm.

 

No, I needed a custom driveshaft for my 4l80 conversion.

I've got 20" wheels on it. I'm not sure what the tire size is exactly but its not a huge tire.

My redline is around 6700.

The gears inside the 4L80 are that long? I figured it must be limited somewhere around 140-160 mph?

 

Overdrive will not hold that much power at WOT, so really third gear is your limit, so around 150ish, assuming you lock the converter.

 

Yea just get some 3.23s in there if you want more top end. Right now with my 4.88s not sure if 120/130 might be it.

 

Thanks.

I'm not really looking to increase any top end with my setup. I was just wondering how fast it actually would be possible to go. Right now it pulls so hard all the way up to 130. I just haven't felt comfortable pushing it past the 130 range, I have other cars that are made to go deep into the triple digits if I get the itch.

 

I have a sierra denali and I've had my gps read 146 big big straight away....my truck no longer sees anything over 85, I do my sound barrier breaking on 2 wheels

 

3.73/31" tire/1:1 3rd gear/6700rpm I get 166mph
3.73/31" tire/0.7:1OD/6700rpm I get 237mph.

the 4l80e/85e OD isnt high gear, its a pretty low gear so far as OD gears go.

The 700r4/60/60e/65e/70e family has a higher 0.70:1 ratio
The 200R4 has a 2.75:1 1st and even higher 0.67:1 OD ratio which is the same as the newer 5l80e/90e trans. These 6 speeds have a very large ratio jump between 1st and 2nd, 1st is 4.03 and 2nd is 2.36:1 which results in 1.67:1 ratio drop compared to the 60e which has a 3.0-6:1 1st and 1.63:1 for a ratio drop of 1.43:1.
The rpm drop from 1st to 2nd of the 4l60e is already horrible, the 6l80e/90e is even worse.

even with aftermarket built shafts, I dont suggest high speed runs without driveshaft loops. They certainly reduce teh carnage that results. I once exploded the extension housing of the trans. The next time, the outputshaft actually sheared off and the flopping driveshaft destroyed a cat, and bent a crossmember. The driveshaft let go at 90mph with 27" tires at 90mph, so that shaft was spinning at 4600rpm.
Most Ive spun my DS was at 122mph which was 4400rpm in OD which was 123mph. The D/S was spinning 6350rpm.
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