WHAT IS THIS SOUND?????its killing me

[muddybuddy]

hey guys, i have an 88 k5 np208 with 8" BDS lift. i got the rear driveshaft lengthened, and plan to get a high angle shaft in the future. thats the background.

alright when driving, i think its the transfer case that makes a sound thats sounds like grinding, maybe like to things of metal rubbing. i can only hear it when my foot isnt on the gas. when my foot is on teh gas, the sound goes away. a buddy down the street has a 90k5 with 6" bds and np241 and experiences the same thing.

any ideas what this is? it doesnt sound good, it gives me the same reaction as nails on a chalkboard.

 

[nvrenuf]

My guess would be that's the sound of a truck wanting a HAD driveshaft. It's most likely a driveline vibration caused by the lift.

 

[MTMike]

My truck did the same thing w/ the 12" lift..... I'm almost positive it was the rear drifeshaft

 

[muddybuddy]

alright, thats kind of what i suspected. its not bad to drive it how it is though right, its jus gonna make that noise? i had the shaft lengthened so the slip yoke is in as far as it is suposed to be. at least its nothing internal. well looks like ill have to get a HAD soon and sell my lengthened shaft on here.

how long does it usually take HAD to build the shaft?

thanks guys

 

[muddybuddy]

yea i forgot to mention taht it does vibrate a bit

 

[bigbadchev84]

are you sure the driveshaft is balanced/ good u-joints?
i have 4inch rear springs.5inch blocks with a sm465/208 the factory transfercase spacers are between the frame and the crossmember and i have no vibrations at all

 

[MudFrog]

Mine does that as well, it's caused by the rear driveshaft not having the correct angle.

 

[Blue85]

This is from bad U-joints, incorrect U-joint angles or a loose pinion.

Lift kits are more generic than the manufacturers want you to think. They will give you the same parts for a K5, short-box, extended cab, etc. and then make you think it's "custom tuned" for your vehicle. They probably only get the angles right for one of the wheelbases in the Chevy fleet. Angle finders are cheap and you don't know anything without one.

You may need to drop the transfer case. Many people do. In the end, any U-joint angle above 13 degrees (+/-) is going to give you some level of vibration.

 

[muddybuddy]

u can still drive with the vibration tho right? im going to get a HAD but wont be able to for a little while

thanks, all this info is very helpful