Vibration/shudder type feeling

[yar02169]

I hope to make this short. New used tires, brakes, rotors, and a couple calipers last year. Transfer case problems in the fall, so it sat all winter. Bought a x-fer case from a bone yard during the winter. Just installed the x-fer case and new parking brake cables. Took it for a test drive and when power is applied, there is a vibration type shudder that I can't detect where it's coming from. Let off the gas and the feeling immediately goes away, re-apply gas and the feeling is back.

Tranny fluid is proper, x-fer case fluid is new (just filled). It struck me that before I parked it for the winter that there was the same vibration, one of the reasons I parked it as I was thinking it was going to explode more than it had already done.

Any ideas? I don't hear anything, it's just a vibration type feeling. Engine revs fine, it rolls fine at speed, it's just when power is applied. I'm tempted to rotate tires to see if there's a change, but if it's tires, it should be felt all the time, correct? I'm stumped, so I'll listen to offers.

Thanks,
Ray

 

[gmcman]

I know that I have felt a shudder on acceleration when I engage 4WD for the first time in a while and I want to say it's the U-Joints on the front driveshaft from the transfer case. Could be what's going on since I believe the Bravada is AWD so that shaft should always be under torque.

 

[yar02169]

Ya, it does have the Smart Trac AWD system. If i remove the front drive shaft, that would let me eliminate or pinpoint where the vibration is coming from. Sounds like a decent starting point, thanks.

 

[yar02169]

Got the front drive shaft out, and the u-joint looks to be dried out a bit. Went for a ride, and there was still the feeling. Took out the back drive shaft, and one of those u-joints is definitely no longer good. Thanks gmcman for you advice.
Off to the car parts store for 3 u-joints. Autozone had a listing for the front drive shaft, but N/A for the rear. I asked for him to look up a Trailblazer, and he had a listing. Now I was confused. Luckily, in the same building there's a Sullivan Tire. I walked in there and asked if he could get u-joints for an 02 Bravada. He had a number, so I asked if he could compare the number to an 02 Trailblazer - Same number, just like I thought. Bought the u-joints and went to change them.
No press, so I tried doing the front drive shaft with my vice, and that didn't survive. I'll stop by my local transmission guy and ask him to change out the u-joints.
I then hope I'm done for a while.

 

[The_Roadie]

The U-joints are locked in at the factory by melted nylon. You need to heat them with a torch to get the locking plastic out of there.

 

[yar02169]

Replaced all three sets of u-joints. One of the rear joints was kaput, the post was worn, dry, and grooved. The front drive shaft u-joint was a pain to get out, but with a 5lb hammer, it didn't resist to long. Melting the plastic out of there takes a few minutes, and then a little extra just to make sure the stuff is out of there and not holding in the u-joint.

Thanks for the help, I was scratching my head trying to figure out the cause of the 'feeling'

PS. A local shop gave me a quote of $225-250 to replace all three u-joints. Way to much to charge, especially when they have the presses to do it quickly. I rather spend the 2-3 hours doing it myself, keeping the cash in my pocket.

 

[hayes]

Replaced all three sets of u-joints. One of the rear joints was kaput, the post was worn, dry, and grooved. The front drive shaft u-joint was a pain to get out, but with a 5lb hammer, it didn't resist to long. Melting the plastic out of there takes a few minutes, and then a little extra just to make sure the stuff is out of there and not holding in the u-joint.

Thanks for the help, I was scratching my head trying to figure out the cause of the 'feeling'

PS. A local shop gave me a quote of $225-250 to replace all three u-joints. Way to much to charge, especially when they have the presses to do it quickly. I rather spend the 2-3 hours doing it myself, keeping the cash in my pocket.

Did that solve the problem? It sounds like it did...