The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Center drive shaft bearing or one piece drive shaft??

AllGoNoShow · 02-09-2022, 06:16 PM

A 4" shaft will also fit in the driveshaft hole for the trailing arm crossmember, if your interested. But, if you go low, you may need to raise the top of the hole to prevent driveshaft interference at max suspension travel (I put up some pictures of what I did on a different thread).

I replaced my one-piece 3.5 driveshaft on my long-bed with a 4" driveshaft when I did a tranny swap-if you look into "critical speeds" of driveshafts, when they get as long as they need to be for a long-bed, you start reaching this critical speed (rpm at which point the driveshaft becomes unstable and starts whipping like a jump rope) of a 3.5" driveshaft around 85MPH depending on specifics of gearing, etc. Jumping up to a 4" driveshaft gives you substantially more RPMs/speed before reaching this point.

02-09-2022, 06:16 PM	#13
AllGoNoShow Registered User Join Date: Feb 2020 Location: Rochester, NY Posts: 200	Re: Center drive shaft bearing or one piece drive shaft?? A 4" shaft will also fit in the driveshaft hole for the trailing arm crossmember, if your interested. But, if you go low, you may need to raise the top of the hole to prevent driveshaft interference at max suspension travel (I put up some pictures of what I did on a different thread). I replaced my one-piece 3.5 driveshaft on my long-bed with a 4" driveshaft when I did a tranny swap-if you look into "critical speeds" of driveshafts, when they get as long as they need to be for a long-bed, you start reaching this critical speed (rpm at which point the driveshaft becomes unstable and starts whipping like a jump rope) of a 3.5" driveshaft around 85MPH depending on specifics of gearing, etc. Jumping up to a 4" driveshaft gives you substantially more RPMs/speed before reaching this point.