Question about AWD T-case/diff :-)

[Goro21]

I'm trying to iron out a pretty serious vibration issue and have a question about our AWD drivetrain. (I plowed through previous threads and found nothing but AWD burnout crap.. so, sorry about the lame question When I have both front wheels jacked off the ground, the passenger side wheel spins freely in any direction. The driver side is much harder to spin and spins the other wheel in the opposite direction. Is this correct? I recently had the transmission and transfer case rebuilt and not sure if these might be causing my vibration.

About the vibration, I thought I had finally figured out what the problem was (driveshaft carrier bearings) and was planning on replacing them this weekend. (I have a real bad vibration between 40-60mph, above or below that its a smooth as butter) We'll, I was home from work today and decided to replace my thermostat. (have the infamous code25 CEL.. coolant temp sensor blah blah blah) I have had a few local shops look at the car for both the "drivetrain" vibration and the CEL in the past. (actually had the thermostat and coolant sensor replaced before) Every time i drove away from the shop the vibration was "almost" gone, it was only slightly noticable right at 50mph. After driving 20-40miles from the shop, the CEL would come back on and the vibrations would slowly starting getting worse and worse, until it maxed out at the whole chassis vibrating apart between 40-60. We'll, after replacing the thermostat today, I cleared the ecu and went for a drive and whattya know, the vibration is back to the barely noticable at 50mph again. I didn't even touch the drivetrain at all ...... WTH?!?!

Now, I'm almost positive.. after driving for 30 or so miles like every other time I have picked the car up from the shop, the CEL will come back on showing code 25 and the vibrations will worsen back to being really bad. I'm curious now, if i clear the ecu every so often, if the vibrations will go away like they have today.

Does anyone have any insight on this, have seen something like this, or know if this is even possible? Could any possible component of the car that would throw a CEL of 25 cause the car... engine?.. to vibrate like this? Im talking about a SERIOUS vibration here, not wheel related (have new rims and tires fully balanced and new kyb agx shocks and eibach prokit springs) but is ONLY speed specific. RPM or gear does not matter at all, this vibration occurs only when the engine is under load (clutch engaged) between 40-60mph.

Thanks for reading guys.

 

[Defiant]

I have a real bad vibration between 40-60mph, above or below that its a smooth as butter

Those are tire shake speeds. Re-balance and check for sidewall bulges.
If you're getting the vibration around 3500 RPM, check the rear balance shaft for being 180 degrees out of phase.

 

[Goro21]

I have two sets of rims/tires (one winter one summer pair) .. all 8 tires are brand new and have been freshly balanced. The vibration I have is exactly the same regardless of which set of rims are on the car. Also, I had an alignment done about 500 miles ago, the vibration was the same before and after. While I had the car up on jackstands earlier I also checked to make sure the wheels were snug, which they all were. So I don't believe I have a wheel bearing issue or anything like that.

Most carrier bearing vibrations Ive read about seem to occur while under heavy load, has anyone had very consistent vibrations at set speeds with bad carrier bearings? The center section of my driveshaft is very easily moved.. from underneath the car, you can push up on the driveshaft moving it up about a half of an inch, or pull it down torward you about a half of an inch. This section of shaft moves VERY easily too, can push it up with one finger. Could this be causing the vibration I have?