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Discussion Starter · #1 ·
*This is a cross-post from the transmission forum but I wasn't getting responses over there so I thought I'd ask here too*

An issue developed with my truck about 3 months ago, I've got a nasty vibration that starts around 20 and lasts to 25mph. It's probably the worst right at 25.

I had the U-joints replaced about 2 months ago which I thought would fix the problem (especially because when I took the driveshaft out the joints were quite sticky/siezed). The new U-joints may have helped slightly, however the problem is still there.

Driveshaft shop said that the carrier bearing was ok, I'm thinking pinion angle maybe?...

...but it doesn't really make sense that my pinion angle would just change one day out of nowhere. This problem literally just started out of the blue, I owned the truck 3 years prior without the vibration.

Do you guys have any other ideas?

I'm going on big trip in a couple of weeks and really want to get this figured out before then, I don't want to break down far away from home.

PS. The problem is exactly the same with either of my sets of wheels so it's not an out of balance wheel/tire
 

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*This is a cross-post from the transmission forum but I wasn't getting responses over there so I thought I'd ask here too*

An issue developed with my truck about 3 months ago, I've got a nasty vibration that starts around 20 and lasts to 25mph. It's probably the worst right at 25.

I had the U-joints replaced about 2 months ago which I thought would fix the problem (especially because when I took the driveshaft out the joints were quite sticky/siezed). The new U-joints may have helped slightly, however the problem is still there.

Driveshaft shop said that the carrier bearing was ok, I'm thinking pinion angle maybe?...

...but it doesn't really make sense that my pinion angle would just change one day out of nowhere. This problem literally just started out of the blue, I owned the truck 3 years prior without the vibration.

Do you guys have any other ideas?

I'm going on big trip in a couple of weeks and really want to get this figured out before then, I don't want to break down far away from home.

PS. The problem is exactly the same with either of my sets of wheels so it's not an out of balance wheel/tire
If these drive shafts are like most, it's possible that the shaft itself is out of balance. A counterbalance weight(s) is often spot welded onto the drive shaft at the factory. A good visual check should ascertain if the weight has come loose.
Should this not be the case, I would check the tranny mounts and the engine mounts.
 

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i saw what you did there!
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when does it do it?

in gear?

out of gear?

coasting?

under acceleration?

kjust because u joints are new now doesnt mean the driveshaft didnt get bent due to locked up seized u joint

it happened to my 91 and is why i had to replace my DS and i went with a one piece one

a locked up u joint kinked the heck out of the rear half of my DS and it was a horrible shaking at low speed acceleration

ruined it

after i replaced u joints i looked at the DS closely and nmoticed it was bent

if a joint seizes up then it probably will bend the DS

and u joints commonly do dry up and seize up

the only other possibilities woul dbe trans mount, tire, carrier bearing

but each one would cause the vibration under different cirumstances

some under load(trans mount or engine mount), some all the time no matter what(tire, bearing)

etc.,

slowly carefully with flat palm across tire treads feel al your tires all way around for any bulging or sinking in the tread

if you feel any then you got a separating tire belt

its pretty common i see this happen alot and it will cause vibration shaking etc
 

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Discussion Starter · #4 ·
fastr68,

great reply, sorry for not seeing it sooner. The vibration is there whether accelerating or coasting (I have an auto).

When I had the U-joints replaced the shop said that the shafts and the carrier bearing looked fine. I specifically asked them to check when I dropped it off and they're a reputable shop (and could have easily sold me a carrier bearing if they had opted to replace it) so I trust that they did check.

One thing that I've heard (read via searching other forums) is that the GM factory joints (with the injected nylon retaining system) do not necessarily centre the same way as aftermarket joints with the clips.

IE, clipped U-joints only go in one way but the OEM ones can be slightly off either way, and therefore the shaft will sometimes need re-balancing when the OEM joints are replaced with aftermaket ones.

What is your opinion on this?


Also, I ordered and just recieved a JTR driveshaft alignment kit. I won't have time to install it until next week unfortunately but maybe that will fix the problem or at least help.
 
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