08 Tahoe Vibration - SOLVED

[Doubeleive]

Bummer! Manual would have been quite rare for sure.

Not to discourage any other comments but you are explaining this well. Needless to say, we have been stuck in circles tracing this down so we appreciate the time and input here.

Can you make any sense of why the vibration would've gotten more noticeable from before the first dealership visit to now?

if they flipped the drive line, yes. easy enough to flip it back

 

[08TahoeVibes]

I don't see any indication on the bolts of the u-joints of the rear driveshaft to suggest that they have been touched recently. They all look alike and not like they have had any tools put on them.

It goes without saying that you obviously know more about this drivetrain than I...

Having one of the front tire jacked up off of the ground; when I spin the wheel, the front driveshaft spins. Is this at all indicative of the 4WD operation? If the truck is in 2HI, is it expected that the front driveshaft to not be spinning or is it always spinning regardless of what is selected on the 4WD dial?

I suspect that it has to always be spinning for the gears to be in sync in the event Auto 4WD calls for power to be disbursed amongst the front wheels. That being said, there has to be a non-moving part that engages this when it's needed.

Always up for learning more about it!

 

[j91z28d1]

I don't see any indication on the bolts of the u-joints of the rear driveshaft to suggest that they have been touched recently. They all look alike and not like they have had any tools put on them.

It goes without saying that you obviously know more about this drivetrain than I...

Having one of the front tire jacked up off of the ground; when I spin the wheel, the front driveshaft spins. Is this at all indicative of the 4WD operation? If the truck is in 2HI, is it expected that the front driveshaft to not be spinning or is it always spinning regardless of what is selected on the 4WD dial?

I suspect that it has to always be spinning for the gears to be in sync in the event Auto 4WD calls for power to be disbursed amongst the front wheels. That being said, there has to be a non-moving part that engages this when it's needed.

Always up for learning more about it!

I think there's 2 or 3 different style transfer cases in these trucks. I honestly don't know which is which. the other guys know all the different part numbers and how they work. i think I have the same one you have. but not sure since I have the hybrid version that seems to always be a bit different.


but yeah, the oem u joints don't have grease fittings on them. depending on which one you have. they can also be held in with nylon, which makes them almost impossible to change without damaging the ears of the shaft.


I don't know all the details that are specific to these trucks. i just dealt with drive shaft vibration in my car from when I got it in high school for a good 10 years of owning the thing. so many shops, replacing parts with money I didn't have. I installed a 3.73 gear in the car cause I was just throwing a parts at it by then as I could save up for them. when I picked it up and it still did it, I took it back to the shop and a younger guy that installed the gear hopped in for a ride. Instantly he's like man, that's a drive shaft not my gear install. that lead me to drive shaft shops, multiple made and never fixed it even thou they all balanced perfectly on their balancers. finally threw a junk yard one in it and bam. first time the car was ever smooth from the first day I bought it.

drive shafts have been a pet peeve of mine ever since.

I mean anything is possible, I could be totally wrong. it's just a guess over the internet that sounds like it matches what I've dealt with.

 

[Fless]

I think there's 2 or 3 different style transfer cases in these trucks. I honestly don't know which is which. the other guys know all the different part numbers and how they work. i think I have the same one you have. but not sure since I have the hybrid version that seems to always be a bit different.


but yeah, the oem u joints don't have grease fittings on them. depending on which one you have. they can also be held in with nylon, which makes them almost impossible to change without damaging the ears of the shaft.


I don't know all the details that are specific to these trucks. i just dealt with drive shaft vibration in my car from when I got it in high school for a good 10 years of owning the thing. so many shops, replacing parts with money I didn't have. I installed a 3.73 gear in the car cause I was just throwing a parts at it by then as I could save up for them. when I picked it up and it still did it, I took it back to the shop and a younger guy that installed the gear hopped in for a ride. Instantly he's like man, that's a drive shaft not my gear install. that lead me to drive shaft shops, multiple made and never fixed it even thou they all balanced perfectly on their balancers. finally threw a junk yard one in it and bam. first time the car was ever smooth from the first day I bought it.

drive shafts have been a pet peeve of mine ever since.

I mean anything is possible, I could be totally wrong. it's just a guess over the internet that sounds like it matches what I've dealt with.

Now that's a lesson on how it can be good to get the shaft!

 

[j91z28d1]

Bummer! Manual would have been quite rare for sure.

Not to discourage any other comments but you are explaining this well. Needless to say, we have been stuck in circles tracing this down so we appreciate the time and input here.

Can you make any sense of why the vibration would've gotten more noticeable from before the first dealership visit to now?

I have no idea if ours has this or not, as I've never cut one open and am not touching the one in my truck till it either falls out or starts vibrating haha. but some have stuff inside them that can come loose.

https://www.jalopyjournal.com/forum/threads/cutting-drive-shaft-down-found-card-board-tube.388088/

 

[Doubeleive]

I don't see any indication on the bolts of the u-joints of the rear driveshaft to suggest that they have been touched recently. They all look alike and not like they have had any tools put on them.

It goes without saying that you obviously know more about this drivetrain than I...

Having one of the front tire jacked up off of the ground; when I spin the wheel, the front driveshaft spins. Is this at all indicative of the 4WD operation? If the truck is in 2HI, is it expected that the front driveshaft to not be spinning or is it always spinning regardless of what is selected on the 4WD dial?

I suspect that it has to always be spinning for the gears to be in sync in the event Auto 4WD calls for power to be disbursed amongst the front wheels. That being said, there has to be a non-moving part that engages this when it's needed.

Always up for learning more about it!

the axles & drive line will spin even if not engaged, the actuator that is screwed into the differential is what pushes the clutch/gear over to provide power when it is activated, when it's not everything is pretty much just free wheeling, you could probably grab it and hold it but I wouldn't recomend it lol

 

[blondie70]

Couldn't you jack all 4 wheels in the air and run front and rear seperately ? See where the vibration is ???

 

[Doubeleive]

Couldn't you jack all 4 wheels in the air and run front and rear seperately ? See where the vibration is ???

risky at best especially at any kind of speed and without a load no telliing if you would even feel it.
just runing it up to 35-40mph off of the ground is kind of sketchy

 

[petethepug]

If the vehicle was off the ground, their’d be no load on the drive train or suspension. You’d never hear a sound driving through the perfect road of thin air.

 

[08TahoeVibes]

I appreciate everyone’s comments, ideas, and knowledge share on this.

We are going to start with replacing the front driveshaft this week and see where we end up with that. More updates to come.