Exploding driveshafts?

[Chert_Detective]

so if the driveshafts are an issue at above say 100mph, do the PPV/SSV get something different? (I suspect not) and obviously they are sold and marketed as a pursuit capable vehicle so???

That's a good question, I asked my buddy who has a ppv. He said ppv is lowered 2wd, ssv is standard 4wd, both stock drivetrain but ppv is rated to 130mph. It is not unheard of to have a factory driveshaft balanced to a higher rpm, the factory tolerance pretty low. Perhaps during the conversion to police use the driveshafts are rebalanced.

 

[swathdiver]

@swathdiver I believe the guys are correct. 4hi, 4lo, 6speed, 10 speed, 30mph is 30mph.

So care to take a stab at why GM changes the OSS when in 4LO? I don't have a clue.

Y'all makin me wanna fab up a driveshaft loop while I'm under it.

Back in the day that was SOP for a 13-second or faster auto.


The SSVs/PPVs have a larger diameter aluminum driveshaft if memory serves and that combined with their shorter wheelbase raises the critical speed and therefore, top speed of the vehicle.

Hey Wes, does the Silvy have a 2-piece driveshaft? @Doubeleive

 

[Chert_Detective]

So care to take a stab at why GM changes the OSS when in 4LO? I don't have a clue.

Ya got me there bud, I have no idea. I may just be overthinking my simple thinking, but the driveshaft speed should be the same at a given mph in one gear vs another. Otherwise the ciritcal speed formula would involve other variables besides mph, final drive, and tire height.

Unless you have a super special diff or reduction planetaries after the driveshaft. In which case I want those haha.

But your tire height isn't changing, the rear gear isn't changing, and the mph isn't changing. So the shaft speed shouldn't change either otherwise your mph would change as well. The only, main, thing that's changing is the engine rpm needed to turn the shaft at the speed necessary for that same mph as before because of the change in gear sequence before the shaft.

 

[randeez]

you are in charge of your own safety .... if YOU think you need it and will forever be hesitant about going over 100 then just order a custom shaft and be done with it if you plan on going over that point often

it could happen, sure. it could be a fluke thing, or it could be driveline angles, vibration, bent shaft, etc. saying that a perfectly good one, in the perfect installation will still explode over *** mph, comes from critical speed+length of the tube material.
https://pstds.com/critical-speed-chart/ for custom shafts atleast. the stock steel shaft sounds like a soda can when you tap on it.

personally never had any problems with stock driveshaft on mine (short awd yukon) the shaft is like 41" long iirc. had it balanced for like 80bux with a local guy. had him shorten, cut to custom length and replace the stock material with something a little thicker throughout its life.

 

[Doubeleive]

So care to take a stab at why GM changes the OSS when in 4LO? I don't have a clue.



Back in the day that was SOP for a 13-second or faster auto.


The SSVs/PPVs have a larger diameter aluminum driveshaft if memory serves and that combined with their shorter wheelbase raises the critical speed and therefore, top speed of the vehicle.

Hey Wes, does the Silvy have a 2-piece driveshaft? @Doubeleive

No it has a big fat ass single aluminum one on the rear

 

[randeez]

So care to take a stab at why GM changes the OSS when in 4LO? I don't have a clue.
@Doubeleive

i dont know about changes, but i think the oss is just used to relay mph info when you're in 4lo (after the tcase reduction) any other time it just looks at the ISS to know speed . its probably physically a different reluctor gear so it doesnt read linear to the ISS