i pulled mine in 3rd gear... everything stayed in one piece!.. ex.cab 2wd 123,xxx miles...

 

2nd gear pull
3.42s and 29.7 tall tires
3rd has to much wheel speed no need to break parts for a number!

 

thats good to know, im about to dyno mine and never thought about that

 

I did the pulls in 2nd like you all suggested. I am pretty impressed with the gains. Tried to do as apples to apples as I could but you know that never works out exactly. I am starting a dyno thread in that section. I gained 35/22rw.

So the guys that run over 120 replace their drive shafts? That is crazy that they come apart.

Does anyone know how much you gain from second to third. I would guess around 5-10. Would be nice to have real numbers. Oh well, I am not putting a drive shaft just for that.

 

when i first had my truck on the dyno i wanted to find out if the hand tuner had a limiter so i had the guy run to 150mph and didnt hit it. stock drive shaft and stock tires 235 75 16's held together fine till this day..... 8 years later and still do 120-130mph highway runs when i can.

 

You guys have to realize that tire size and gearing have no effect on driveshaft speed. Your shaft speed will equal engine rpm in 3rd gear. Diff ratio and tire size are after the shaft. If you have a long one piece shaft, it's iffy, 4wd takes about a foot off the length, as does being a rcsb vs ecsb. I've dyno'd my ccsb 4wd and rcsb 4wd with stock shafts in 3rd.

 

Dang, that is a good point. The drive shaft sees no more rotational speed per trans gear? Seems that with the trans gearing changing the output speed would change? If not then the real deal is just the tires then. I doubt that the tires are rated to 160 but I would like to dyno in 3rd to get more data points and real numbers. Thanks for the input.

 

Built drive shaft, stock wheels and tires, 3rd gear...been to 150mph on the dyno many times. Holding that speed causes issues, but for the duration of a dyno pull I wouldn't worry about it.

 

Of course it changes the DS speeds...
They are saying that rear end ratios and tire size determine your MPH..

Ive been 157-158ish on my stock 2 peice driveshaft on the interstate
never again tho.

~4700 in 4th with the converter locked = 6250 RPM for the driveshaft

 

OK, I thaught Joeyc's post was for the people talking about drive shafts breaking due to rotational speed. Not tire speed. I know what determines you mph. The concern seems to be for the drive shaft. In the lower gears wouldn't the drive shaft speed be higher than in 3rd considering that 3rd is one to one. In overdrive the drive shaft would be going even slower. So for the drive shaft it's self you are better off in 3rd.