NEED HELP Rear vibration

[Mike w]

Hey all my truck has a vibration heard in the rear and I'm pulling my hair out to find out what it is I have replaced the rear axle still there it does it at 30mph and above I was thinking it was the transfer case it has play where the rear driveshaft goes into the tc the easiest way to explain the vibration is like hitting washboard ruts. Please help me if you have had a similar problem.

 

[Sparky]

U joints?

 

[Mike w]

No, I changed those already. I have a low mileage transfer case already if I do have to change it.

 

[Wooluf1952]

Lost a weight from the drive shaft or a wheel?

 

[Sparky]

Is the play in/out or like up/down/side to side?

If there is any appreciable play in the up/down/side to side movement in the case I'd suspect the output shaft bearing is going out. No first hand experience with this, just a suspicion on my part.

 

[Mike w]

The play is up and down and I checked all weights on shafts and wheels

 

[Mike w]

Will play at the tailshaft on the t case cause a vibration in the driveline?

 

[Mooseman]

Renamed thread for more/better responses.

Is it steady or on and off? I remember from a long time ago a bad torque converter clutch would vibrate badly on engagement, like clutch chatter.

 

[Mike w]

It's steady after 30 mph good rename too thanks

 

[mrrsm]

I've been thinking about your first post... and had some questions come to mind:

(1) When you say you replaced the "axle"... did you mean just one on a particular side... or both axles during the repair? Was the replacement part... Used... or Brand New?

(2) Do the axle part number(s) match the original in every respect as well as the length dimensions... and if you still have the one you removed... can you tell us why it was necessary to change out the axle?

(3) Did you get the chance examine the old axle gear-spline tines with a bright flash-light for anything eccentric in its wear patterns that might indicate a problem with the hardware still inside the differential?

(4) Did you replace the Timken Axle Roller Bearing on one side only with a brand new one?

(5) Did you unbolt or shift any other rear suspension components during this repair... and if so...have you had a chance to double check that those items went back in just as they were prior to performing the repair?

 

[Mike w]

I changed it with a new complete axle the one that was in my trailblazer was shot fluid was black with lots of metal shavings stuck to the magnet.. the rear axle I had was a GU6 I installed a GU6 same as what was in it same 3.42 gear ratio all bushings were in great shape and shocks were OK as well I had the transmission replaced at Napa auto care center a year and a half ago. I have no idea what the problem could be now the u joints are new and the driveshaft is in balance I am going to replace the transfer case this coming weekend I already have an extra one

 

[Mooseman]

GU6 denotes the axle ratio. Is it a limited slip? Or a G80 locker? Open diff? What are the tires like? Old, new, more wear on one side or the other, good or cheap brand?

 

[mrrsm]

Following on with @Mooseman 's Logic... if the Rear End has a limited slip differential...GM requires a special additive to be induced with the Mobil1 75-90 Gear Oil...assuming it has not already been filled. It would be very helpful if you could take a digital image of your vehicle's RTO Plate (Driver's Door Jamb and or inside the Passenger Glove Box Lid... not sure about one being glommed inside the Center Console Lid) and post it here as there are people with the wizardry to quickly decode the features on manufacturing of the vehicle that are of import to our understanding.

I realize that your definition of "New" means just that... "BRAND NEW"... But in the case of these complex rear end gear boxes... you would be surprised how many of them are sold...and then wind up being installed...FUBARed and then returned and re-stocked on the shelves because the original purchaser failed neither to install it correctly... nor to set the proper "Gear Lash" between the rear axle Hypoid Gear...and the Differential Ring Gear...and damaged their working relationship as a result. In many cases... they flush out the gear box to conceal the metal particle damage and just put the case cover back...leaving the gear box...Bone Dry for the next unsuspecting customer to discover! One of our other Members... I believe he goes by @Dogfish24 ... is also known as "Chris Fix" and is renown for his excellent Youtube Repair Videos... one of which covers a How-To R&R the Rear Differential Cover Plate...Clean, Re-Seal and Re-Install the item and the how to properly fill the gear box.... This is worth viewing:

Unless this has been cleverly concealed... you should be able to determine whether anyone other than the factory assembler has been past the Rear End Cover Plate if you can see that all the original 10 or more Cover Plate Bolts have been removed and left evidence that this has occurred by the absence of paint around the Bolt Heads or shiny metal or damage to the bolt heads. Unless you discover some other reason for the clunking and bumping action first...keep this issue in mind... should you decide to investigate further the innards later on.

The following link leads to an RTO Translation Code Listing PDF for GM Passenger vehicles...and as sure as there are "Carts to Horses"... One or more of our astute members will chime in and provide you with the relevant one for trucks and SUVs. Still... this one is posted here to show how complex these things can get in de-cyphering the myriad Alpha-Numerics and it might still come in handy for those of us with other GM Camaro and Firebird F-Body Carline Series Vehicles for off-topic repair needs:

http://www.marshu.com/images-websit...codes/gm-firebird-camaro-GM-RPO-car-codes.pdf

 

[HARDTRAILZ]

Following on with @Mooseman 's Logic... if the Rear End has a limited slip differential...GM requires a special additive to be induced with the Mobil1 75-90 Gear Oil...assuming it has not already been filled.

The G80 is not a limited slip, but is a locker and has no need to have the additive added. Most of this platform did not have a LS but some did in the form of a G86 but if he bought the common Mobil 1 75/90 like this

the LS on it designates that is has the additive in it. Many use only this, but some still add a modifier.

 

[Mike w]

Tires are new it's an open diff so my next step is to pull the diff cover and do a through inspection on the axle just to be sure it's not defective because it is possible to buy a part that is bad. the vibration is so bad at times that my roof rack vibrates

 

[HARDTRAILZ]

You check trans and TC mounts? Long shot, but I did have one fail on me

 

[mrrsm]

Wow @HARDTRAILZ ... Great Idea...You are so right! If the Mount Rubber has completely separated...under hard acceleration...the engine torque would warp the u-joint at the tail take-off shaft enough to play hippity-hoppity up and down like a jack-hammer. Also... the Tranny Mount could appear sound as dollar, for all intents and purposes... until it gets jacked up enough to see if any daylight (or flash-light) comes shining through...and fixing that item is a damned side easier than having to pull the RA Pan. Good call...

 

[Mike w]

I'll check the mount I suspected it was an issue too. I have a whole bunch of good parts for my truck so in the end I should be able to fix it lol when I figure it out I will leave an update it will be sitting until Saturday when I have spare time to finish it so by late Saturday I should have the answer to this problem. Off topic but everyone keeps telling me to sell it and I say no not my GMT I love my TB.

 

[Mike w]

PROBLEM SOLVED I swapped the transfer case and all the vibration is gone now rides really smooth now thanks to everybody.

 

[Mooseman]

I never would have suspected the TC. Good on you for finding it.