[1 Lucky Texan]

are the tires in good condition, recently balanced?

at those speeds though, it would be quite possible to have axles or driveshafts and other components contribute to vibration. And weak struts may also have less ability to keep tires firmly planted. Bushings are also getting worn so, it may be tricky pinning it down.

Is this a seat-of-the-pants vibration? is the steering wheel vibrating? if you 'coast' in neutral is the vibration still there?

If you regularly travel at speeds like this, I believe there are ways to have a highspeed balance done on the wheels. And a 'tuner' with a 4WD dyno might be able to help you.

 

[bwalton]

More than likely the OEM front half shafts were replaced with aftermarket half shafts because the inside CV joint boots split open and threw CV grease all over the exhaust pipes, the catalytic converter, the turbo and engine compartment. Aftermarket half shafts have been known to have balance issues, which cause vibration at higher speeds. Start with dynamic tire balance, find a tire shop that can check tire round-out with a dial gauge, front and rear wheel bearing free-play, loose or worn suspension components, drive shaft thrust bearing, brake rotor balance, alignment (look at your tire wear for problems), worn engine and transmission mounts, a blown strut and finally the half shafts themselves.
Lastly; are you sure the front half shafts (HS) were replaced or were the OEM HS’s CV joints repacked with grease and fitted with new boots.

Good Luck!

 

[subiesailor]

More than likely the OEM front half shafts were replaced with aftermarket half shafts because the inside CV joint boots split open and threw CV grease all over the exhaust pipes, the catalytic converter, the turbo and engine compartment. Aftermarket half shafts have been known to have balance issues, which cause vibration at higher speeds. Start with dynamic tire balance, find a tire shop that can check tire round-out with a dial gauge, front and rear wheel bearing free-play, loose or worn suspension components, drive shaft thrust bearing, brake rotor balance, alignment (look at your tire wear for problems), worn engine and transmission mounts, a blown strut and finally the half shafts themselves.
Lastly; are you sure the front half shafts (HS) were replaced or were the OEM HS’s CV joints repacked with grease and fitted with new boots.

Good Luck!

^ What he said - after market cheaper CV joints and axles are famous for being a major pain in the ass regarding vibration and poor fit. What generally happens is when someone tears a boot on their stock OEM axles ie CV the local leo likes to replace them given they can get a very good core value for the stock OEM axle and they can cheap out and put a cheaper axle back in without messing with rebooting the original axle.

The #1 best thing to do - is to keep your original axle and simply reboot it as soon as possible to avoid any road debri damage to the CV joint. If the CV Joint gets damaged then replacing with stock OEM axle is the best fix or you'll more than likely be doing it again shortly when the after market axles cause issues.

 

[bwalton]

Before you go to a tire store or mechanic determine if it is a drive-line or suspension vibration. Read 1 Lucky Texan’s post about pinpointing the vibration to either the steering wheel or your seat cushion. The best way to pinpoint the vibration is to drive the car on the freeway at 80 MPH (or when you feel the vibration) then shift your transmission into neutral and coast for about a minute. In general, if the steering wheel vibrates than it is a suspension problem or if the vibration stops while coasting at 80 MPG, than more than likely it is a drive train problem. Note; your OBXT has (4) half shafts and one drive shaft coupling the transmission to the rear differential. If the vibration stops when coasting in neutral than you have narrowed the problem down to either the drive shaft thrust/propeller bearing, the bolts or cross bracket supporting the thrust bearing or the engine/transmission mounts. I believe that all of the half shafts spin with the wheels when coasting in neutral so pinpointing the vibration down to a half shaft will be very difficult.

Caution: I know you can shift into neutral and back into 5th gear with a manual while traveling at freeway speeds without damaging the transmission or the AWD system; however I’m not sure if you can do the same with an automatic. Check your owner’s manual just to be safe.

 

[subiesailor]

If the car is running the AT gets fluid pumped through it so kicking to neutral in the AT for a short distance won't bother it. Shut the engine down and coast at speed yes the AT might get a little angry given no fluid is pumped through it to keep the parts lubed and cool etc.

 

[subiesailor]

Also the number one cause with any vehicle to check into is tire balance and tires being round vs say egg shaped etc. My first car with Continental tires on it since the mid 80's the 2010 OB - the continentals CANT hold balance beyond about 9000 miles after which point they have required some very large changes in tire balance weight to get them balanced again! Even my tire guy says that this large change in weight is not very common and he questions the quality of the tires. Also one tire has slowly gone out of round over the past 20K and at this point can only be put on the rear given when on the front end it shakes the wheel regardless of what speed your going.

Our VW with a brand new set of fairly pricy Michelin's on it had to go back three times before they sorted out the vibration issues - three tires were out of round and they had to get a different more experienced guy to balance them given the person that was balancing them was putting the weights in the wrong location on the light weight aluminum wheels which just the location of the weights was causing issues.

 

[swipeys]

Subie - you may have already answered this so apologies if this is redundant but what brand do you recommend instead of the Continentals? I just bought a '13 OB with Continentals. Would be curious to know what you thought about a better brand for down the road once I ride these Contis down. They seem to be ok but I am not sure I would even know if they stunk.
Thanks

 

[subiesailor]

Swipey - each tire model regardless of maker can have issues. Tires are made with a pretty low tech process they are all made the same way.

All you can do is find as many reviews on the EXACT model tire your looking to use and make a call based on the feedback your seeing. Given how poorly the Continentals hold balance hands down I'm not going with this particular model tire as a replacement!

BFG Touring tire is offered at a pretty competitive price and so far all the reviews and people I know that have them have been impressed by the tire. Even the Camero owners who beat the living crap out of them. FAR FAR better consumer feedback than the Continental tires on our outbacks which have nearly every OB owner looking to replace them with a different brand or model tire.

 

[bwalton]

New tires fresh off the assembly line are not perfectly round nor are the new wheels they are mounted to. That why Tire and Wheel MFR's put marks or drill valve stem holes at high or low spots on their products. Each MFR I.Ds. their high or low spot differently, therefore the person mounting the tire to the rim must position the tires high spot to the rims low spot. Most tire shops in my area do not have a dial gauge clamped to their dynamic tire balancing machine so they try to sell you 4 new tires instead of repositioning the used tire’s flat spot on the rim’s high spot. Some shops will rotate the used tire on the rim in 90 degree increments until the vibration is fixed.