Vibration when I let off accelerator.

[terbronco7]

I have a vibration really only notice it when I am above 40 mph and I let off accel, I thought it could be my wheels and tires but have since got new rims and tires, its better but still there. Any ideas as to what is causing this?
Thanks. It is a 4 speed with granny if this helps any.

[63burban]

Check your universal joints on your drive shaft, worst scenario is the carrier bearing or pinion bearings.

[PGSigns]

Do you feel it in the front or back of the truck?
Jimmy

[terbronco7]

Originally Posted by 63burban

Check your universal joints on your drive shaft, worst scenario is the carrier bearing or pinion bearings.

Thanks I will be replacing those this weekend.

[terbronco7]

Originally Posted by PGSigns

Do you feel it in the front or back of the truck?
Jimmy

Its hard to say, seems like its more center of truck. if I depress the clutch it gets better but still there as well.

[Keith Seymore]

Originally Posted by terbronco7

I have a vibration really only notice it when I am above 40 mph and I let off accel, I thought it could be my wheels and tires but have since got new rims and tires, its better but still there. Any ideas as to what is causing this?
Thanks. It is a 4 speed with granny if this helps any.

Driveline disturbances are load dependent. They can appear on drive (steady state), accel and/or coast (any and/or all of the above).

Tire/wheel disturbances are not throttle dependent.

Sounds like driveline to me (u joints, or angles).

K

[old cool]

Please read "noises in drive line" . I posted last week. Gotten lots of great feedback. I have similar problems. Scoop is, trial and error fixups could be expensive.
My sound is most profound when I push the clutch in between shifts and then while rolling in 3rd gear on flat surface(i have 3 speed). When I push the accelerator down is makes more of a normal sound (working engine and trans). When I let off or just drive at normal speed in 3rd without pushing it, it goes vrrrrrrrrr with some fluctation as I intermittently touch gas pedal to keep speed maintained. Sound never stops. NOTE: Pushing down on accelerator is not when it drives me nuts. It's while I'm cruising along and between shifts. Oh yea, while driving down hill I put the truck in nuetral and it did get quieter but still heard the sound. I will be watching your post.

This may be out in left field, but I wonder if tie rods and poor ball joints would cause wheel bearings to shift in and out and this cause the vrrrrrrr. Up to a point I think it could be a problem -- but then why would it quiet when I was going down hill in neutral? I think I've answered my own question. Yea, back to drawing board.

[old cool]

Keith Seymore. I like the logic to your comment. I believe you responded to me as well. "old cool"

[geezer#99]

Originally Posted by terbronco7

I have a vibration really only notice it when I am above 40 mph and I let off accel, I thought it could be my wheels and tires but have since got new rims and tires, its better but still there. Any ideas as to what is causing this?
Thanks. It is a 4 speed with granny if this helps any.

When you do u-joints check your pinion angle.
Usually when you back off the loud pedal at speed and it vibrates it's the pinion angle. The pinion drops slightly making the u-joint vibrate.
If you've lowered your truck your pinion angle could be off.

[PGSigns]

Pinion is not going to move much on a trailing arm truck. If the pinion bearing is going south along with anything from it to the clutch it could be causing the issue. Since it gets better when you push in the clutch that is taking the load off the driveline. I would check the oil levels in the trans and rear and look for anything that is worn out.
Jimmy

[terbronco7]

All these will be checked truck was lowered, I think rear is stock front def not PO did this, as for oil in tranny it def makes alot of noise where if at all can I put oil in the standard 4 speed with granny def sounds like it needs it for sure.

[luvbowties]

Originally Posted by PGSigns

Pinion is not going to move much on a trailing arm truck. If the pinion bearing is going south along with anything from it to the clutch it could be causing the issue. Since it gets better when you push in the clutch that is taking the load off the driveline. I would check the oil levels in the trans and rear and look for anything that is worn out.
Jimmy

Had a good-mechanic-friend tell me when I was a kid[we got our driv. lic. at 14 yrs. old] that the "back side" of my diff'l gears were worn? Had me verifying his diagnosis at the other garages in nearest town before he laughed heartily at my having taken him so seriously.
Sam

[spacedebris]

lots of good advice here. I dont know if this will qualify but here goes. You may also want to check the exhaust. My grandfather had a similar issue a number of years ago where he would get a vibration when decelerating. turned out to be one of the exhaust hangers had wobbled out a little and when decelerating it allowed the whole exhaust to vibrate. By pushing the clutch the RPM would fall off and the vibration would get better. Just something else to check.

[terbronco7]

Originally Posted by spacedebris

lots of good advice here. I dont know if this will qualify but here goes. You may also want to check the exhaust. My grandfather had a similar issue a number of years ago where he would get a vibration when decelerating. turned out to be one of the exhaust hangers had wobbled out a little and when decelerating it allowed the whole exhaust to vibrate. By pushing the clutch the RPM would fall off and the vibration would get better. Just something else to check.

Thats interesting I will check that out as well. Thanks