Exploding driveshafts?

[ls1frc]

Do us SUVs with 4x4 have the same exploding driveshaft issue over 100 mph?

I am modding my engine to about 420 rwhp and this concerns me to say the least.

 

[avalonandl]

If you intend to go over 100mph routinely get custom shafts made.

 

[ls1frc]

If you intend to go over 100mph routinely get custom shafts made.

Thanks.

I won't on the street, but this truck may trap close to 100 in the 1/4. I'll go from time to time.

 

[Foggy]

I think you'll be fine at that speed and power level with good stock type parts
that are in excellent condition... I'm upgrading all my U Joints to the spicer
HD Joints without the grease zerk - no grease zerk means they are stronger, but
you can't maintain them. Dana/Moog/ Spicer - just find the HD versions w/o the
zerk

 

[swathdiver]

Do us SUVs with 4x4 have the same exploding driveshaft issue over 100 mph?

I am modding my engine to about 420 rwhp and this concerns me to say the least.

The critical speed of our driveshafts is mathematically 4,556 rpms. That comes out to 122 MPH with the tires worn down to 2/32nds tread or 45 MPH with the same tires in 4LO.

If you want to go faster, you need a thicker and or larger diameter driveshaft.

The critical speed of the front driveshaft is 5,000 rpms which is good for 134 MPH or 50 MPH in 4LO.

The driveshaft in my truck is steel, .083" thick with a 3.5" diameter and tube length of 53-1/2 inches. Yours should be the same.

 

[drakon543]

f it and send it lol

 

[intheburbs]

I've had my 2500 up to an indicated 120, once.

Was just curious what she could do. The shocking thing to me was how I could feel the front end getting light due to aerodynamic lift. This is a 6500-lb truck, and she was getting floaty. I would guess I have a heavier duty driveshaft, but yes, if you intend to do it multiple times, an upgrade might be in order.

Do the Denali trucks get an upgraded driveshaft for the 6.2? That's 400 HP. If you're going for 420 rwhp, that's 500ish at the crank, I'd be looking at upgrades to the driveshaft, u-joints and rear end.

 

[ls1frc]

Thanks all. I am going to set my speed limiter in the tune to 105 MPH and forget about it.

This is something that may happen once a year. All I wanted with this truck was for it to not be anemic from 0 to cruising speeds and maybe to have some fun with a civic or something lol.

 

[RST Dana]

@swathdiver i thought the 4w low selection caused gearing changes in the TC. Are you implying it does something else since 45 mph in low is the same scenario as 122 mph in HI. Driveshaft speed should be correlated to wheel rotating speed no mater which selector your TC has correct? I may be confused. Educate me.

 

[iamdub]

All I wanted with this truck was for it to not be anemic from 0 to cruising speeds...

Word. Acceleration>top speed

...and maybe to have some fun with a civic or something lol.

C'mon! Aim a little higher than a Civic!

 

[ls1frc]

Word. Acceleration>top speed




C'mon! Aim a little higher than a Civic!

Well considering my cammed/heads/header 5.3 got smoked by a civic a month ago, I'm starting small lol.

 

[drakon543]

Well considering my cammed/heads/header 5.3 got smoked by a civic a month ago, I'm starting small lol.

depending on the civic you might get smoked every time. people go for either all looks for those or crazy power in a light chassis. im aware there is even an awd swap for some of the older ones.

 

[swathdiver]

@swathdiver i thought the 4w low selection caused gearing changes in the TC. Are you implying it does something else since 45 mph in low is the same scenario as 122 mph in HI. Driveshaft speed should be correlated to wheel rotating speed no mater which selector your TC has correct? I may be confused. Educate me.

I'm not sure how to explain it, with my set up, at 20 MPH the main driveshaft is turning 727 rpms in all gears. In 4LO is turns 1949 at the same speed.

I made a calculator in Excel that I can send you if you want to manipulate it.

 

[RST Dana]

I'm not sure how to explain it, with my set up, at 20 MPH the main driveshaft is turning 727 rpms in all gears. In 4LO is turns 1949 at the same speed.



I made a calculator in Excel that I can send you if you want to manipulate it.

View attachment 256090

Unless you are changing diff gear ratios, the driveshaft rotation vs axle rotation is always the same. 3:43, 3:08 etc. I can’t see how changing my TC to low does anything to driveshaft speed. It would only cause internal TC parts to change speed.

 

[Doubeleive]

well I can tell you I drive well over 100 quit often, the average highway speed around here has increased lately a lot of people are doing 95 without a bat of the eye
I have driven at 137 for extended periods of time many many times traveling around the western half of the country
never had any driveshaft problems, not saying it can't or hasn't happened to others but I have done it multiple gm suv's & pickup's as they all top out at 137 if you can get one above that you are doing good. I have always been more concerned with the tires being the correct speed rating than the driveshaft

 

[intheburbs]

I'm not sure how to explain it, with my set up, at 20 MPH the main driveshaft is turning 727 rpms in all gears. In 4LO is turns 1949 at the same speed.

The transfer case is upstream from the driveshaft. The driveshafts are directly connected to their respective axles. Transfer case setting, whether LO or HI, has no impact on driveshaft speed. The driveshaft is turning the same speed at 30 mph whether you're in LO or HI.

But yes, a friend of mine who was a transmission validation engineer, who worked on the GMT900 platform, said the most likely failure at extreme speeds is the driveshaft. They blew multiple ones during validation. One time it punched a hole through the floor right behind the driver.

 

[donjetman]

x3 what Dana & Bill said

 

[ls1frc]

depending on the civic you might get smoked every time. people go for either all looks for those or crazy power in a light chassis. im aware there is even an awd swap for some of the older ones.

This was just some bone stock high 14 sec civic. I'd like to be able to dip into the high 13s when I am done with my engine swap.

 

[avalonandl]

Civic weighs half your tahoe does

 

[swathdiver]

I agree with you all in theory, next time I take the truck out, I'll fire up the Tech-2 and stick it in 4LO and see what the driveshaft speeds are. Won't be the first time I've been wrong! LOL

Wes, there are more than a few pickup owners over on the GM-Trucks thread that have blown their driveshafts up once they hit the magic speed of 112 MPH or so (don't remember exact number but are several threads about them) Those were all K2s if memory serves. @Doubeleive