Strange vibration while cruising?

[JHelf]

Yesterday my Sy starting making this weird vibration/grind while cruising. It only happens like 35 miles per hour and only when I let off the gas. Anytime I'm accelerating the noise is gone but first thing I let off the gas it starts. If I get back into the gas it goes away. I'm going to get under there today and check things out, planning on taking out the propshaft and driving it to see if the vibration is still there. It is definitely coming from the front as I can feel it in the gas pedal and the dash also vibrates a little when it happens.

If you have any tips on things to check to fix this I would appreciate it. Thanks,

 

[Don W.]

Re: Strange vibration while cruising?

Basic tip: High speed vibration = driveline, low = tire. Check for missing weights on wheels. Do you feel it in the steering wheel? From what I've seen here removing the front driveline for a test is a smart move.

 

[George Blake]

Re: Strange vibration while cruising?

When accelarating it kinda goes away, slowing down or constant speed?

After checking tires for a wheel weight or bent rim, remove front prop and test drive, or it's possibly in the rear yoke(bent)(basically rear driveshaft).

 

[JHelf]

Re: Strange vibration while cruising?

Well just got back from working on the truck. I took out the front propshaft and the noise remained. It makes the noise between 30 and 55 when you let off the gas. I got the truck up on jackstands, had a friend get in it and accelerate up to 35 and let off the gas. The noise is definitely coming from the transfer case. I had to wrap up today but I plan on checking the fluid level tomorrow, any other specific things to checks?

All help is appreciated.

Thanks,

 

[92Ty#1524]

Re: Strange vibration while cruising?

Check the main drive shaft front universal joint.

 

[ircwet]

Re: Strange vibration while cruising?

how about T/C shudder ?does it happen in 2nd to 3rd cruising around 45 ? When it vibrates tap the brake and ride it a bit and see if it goes away...

 

[92Ty#1524]

Re: Strange vibration while cruising?

how about T/C shudder ?does it happen in 2nd to 3rd cruising around 45 ? When it vibrates tap the brake and ride it a bit and see if it goes away...

I see where youre coming from since I recently had the same problem but I believe he said that the vibe arose when he let off the gas, not while giving it. Then again, I could be and am often wrong.

 

[JHelf]

Re: Strange vibration while cruising?

how about T/C shudder ?does it happen in 2nd to 3rd cruising around 45 ? When it vibrates tap the brake and ride it a bit and see if it goes away...

It happens between like 30 and 55, and it does go away if you ride the brakes a little or give it gas. And the noise is definitely coming from the t-case.

 

[ircwet]

Re: Strange vibration while cruising?

but if you hold the brake on and still speed up see if it goes away...Well I have a 2800 stall and it has that that problem....By holding the brake and lighting up the tail lights it disengages the lockup on the T/C....But it will shudder or shake during normal driving enless I keep hier speeds.

 

[JHelf]

Re: Strange vibration while cruising?

If I give it gas, the noise goes away. Actually if I just tap the gas pedal for a second and then let off again, the noise goes away.