2001bowtie

Hello CF,
My name is Zach and I have a 2001 Chevy Silverado 4wd. It has a 6.0 in it and it also has the NV4500 5 speed manual transmission in it. A couple weeks ago i noticed a vibration coming from the undercarriage. The vibration would happen whenever i would hit about 70 mph accelerating and mainly whenever i would let off the gas and coast at that speed. I replaced the rear drive shaft U-Joint that goes into the transfer case and that took care of the vibration whenever i would let off the gas and coast. But now it still vibrates whenever i accelerate around 70mph or higher. The vibration will vibrate under the drivers seat when it happens but once i stop accelerating it stops vibrating. I can not only feel it but the passenger riding with me can also hear the vibration going on and so can I. I do have 33s on the vehicle but it is not a tire or lift issue I do know that. Any ideas??

Thanks in advanced for your input and help!

73shark

Welcome to the forum.

So it's not a tire balance problem?

How about the other U-joints and CV joints?

Post in the Silverado section for more views if you haven't already.

2001bowtie

Thank you 73shark for your response. I honestly haven't checked the wheels for a imbalance. I will do that tomorrow and check and see how they are. The ujoint that goes Into the transfer case I replaced and the lower one was also replaced a couple months ago. I checked the cv boots and they seem perfectly fine. There are no cracks or tears In the boots.

tech2

did this vibration come on all of a sudden or after some work?


if the front and rear u-joints in the rear driveshaft are good; and I know you said its not the lift....how much lift do you have? I would measure the driveshaft angle.? 3+*??? I wondering if you have to much lift . When you accelerate, the torque will further increase the driveshaft angle. large lifts kits will require shimming to reduce this angle on the rear diff snout.


I have seen the t-case output shaft bearing get sloppy and cause a vibration but this shake was there all the time.

2001bowtie

Tech2 it has a 6 inch lift. It just came on all of the sudden but it's coming from the transfer case I'm pretty confident off it. When you say the output shaft bearing, that's what I'm thinking it is. It was a slight vibration at first but now it's all the time at 70mph+ unless throttle is released. So I'm glad you mentioned that. I'm thinking the bearing is getting worse and that's why I'm noticing it more and more. I'll have to replace that and give an update! Thanks all. I'll do the work and get back for an update.