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Discussion Starter · #1 ·
Greetings- Since owning my jeep for about 4 months now, I was averaging about 17 miles per gallon and it's now getting less than 16 (about 15.9). I really just drive it to work and back home which is around 16 miles RT so my driving speed and route are always the same and I use the same gas station for all fill-ups. Any ideas on that drop in mpg?

The biggest issue- which I've tried to fix per a "jeep guru's" advice, hasn't worked. At a specific range in speed, 30-40 mph, there's a feeling in the wheel and pedal as best described as a shudder or a shimmy. It happens all the time but it goes away once I move past 40. At the advice of the supposed jeep guru, I got new tires (which were necessary) and replaced the rear drive-shaft. Sadly, none of that has solved this issue. It's really annoying- I haven't had a "smooth" ride in the jeep since I've owned it. There isn't a noise, doesn't pull when braking, nothing to do with a balance or alignment. I've read about "misfiring" which would mean new spark plugs but I'm not sure how that relates to the shimmy at those specific speeds. I'm not a mechanical guy at all so any thoughts about this would be really helpful. I'm open to looking at anything but I don't want to keep throwing money at an issue that doesn't resolve the issue- like the expensive rear drive shaft. By the way, it's a 2010 Sport 2-door, auto transmission. Cheers!
 

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possible transmission or torque converter issue..... Try turning off overdrive at those speeds and see if the feeling goes away.
 
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Speed related vibrations are almost always a balance issue. It could be a tire / wheel balance issue. It could also be a brake disk balance issue, a drive shaft balance issue, or U joint issue. But it is usually a balance issue.
I would not suspect a drive shaft balance issue, usually those balance issues are higher in frequency due to the faster speed the drive shafts spin at. But it could be.
Are the wheels the stock wheels or aftermarket wheels? If they are aftermarket wheels make sure the star washers that the factory uses to secure the brake discs during assembly have been removed.
The joys of any used vehicle include figuring out what the previous owner did to it or didn't fix.
 

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Discussion Starter · #4 ·
possible transmission or torque converter issue..... Try turning off overdrive at those speeds and see if the feeling goes away.
Thanks- I think (not 100%) but that I leave O/D off at all times. If I'm mistaken, I'll try that tonight.
 

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Discussion Starter · #5 ·
Speed related vibrations are almost always a balance issue. It could be a tire / wheel balance issue. It could also be a brake disk balance issue, a drive shaft balance issue, or U joint issue. But it is usually a balance issue.
I would not suspect a drive shaft balance issue, usually those balance issues are higher in frequency due to the faster speed the drive shafts spin at. But it could be.
Are the wheels the stock wheels or aftermarket wheels? If they are aftermarket wheels make sure the star washers that the factory uses to secure the brake discs during assembly have been removed.
The joys of any used vehicle include figuring out what the previous owner did to it or didn't fix.
I was hoping with the new tires the balance issue would've been perfect but I get that "errors" can occur. I recall after the drive-shaft install that the u joints looked good but I can't say that they were inspected for being balanced. These are standard size wheels and the jeep is in stock condition. Appreciate the comments.
 

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Discussion Starter · #6 ·
Also was told maybe engine mounts might be loose? Differential? To say the jeep shakes is too dramatic, it's a skidding, dragging, shimmy that you unmistakably feel at those speeds. Such a hard feeling to describe but one that is consuming me.
 

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Just try in lower gear and see if it is speed or rpm dependent
If happens
Same speed regardless of tranny gear = speed dependent

Same rpm rpm refused less of vehicle speed then it is rpm dependent

If truly vehicle speed dependent it ain’t torque converter or motor mounts as speed dependent vibration is tranny output back

But if engine rpm dependent then look mid tranny forward

My wag is tire balance or damaged rim
Try rotating/swapping tires front to rear see if it changes ie more or less felt in steering wheel


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The reason I asked about the wheels, if they were stock wheels or aftermarket wheels, is the stock wheels have recesses in the back side of them that clear the star washers that hold the brake disks on while most aftermarket wheels do not. If you have aftermarket wheels, regardless of size, you should remove those star washers, or they can cause the wheels to wobble slightly as they rotate causing a weird vibration much like what you describe. That can also happen if a wheel is bent or out of round.
The idea of manually shifting the transmission to see if it is rpm dependent or speed dependent is a good one as well.
 

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Discussion Starter · #9 ·
I would've hoped if they found a damaged rim at the time the new tires went on they would've said something but I guess one should never rely on assumptions. I'll give it a go in 2nd gear during lunch- very anxious to see (and hope that sheds some light). Sadly, my love affair with the jeep is waning- all due to this so far, unsolvable issue. Really appreciate all of your comments.
 

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Discussion Starter · #10 ·
Was also told to remove the front DS. Since the rear is brand new, I guess it wouldn't hurt to try removing the front DS- if the shimmy goes away, problem solved. If it persists, problem not solved.
 

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Guzzmoto is not talking about a damaged wheel. What he is referring to are the clips that are put on the studs to hold the brake disk in place while the axle in on the assembly line before the brake calipers are installed. Once the brake calipers are installed, the clips are not necessary but are left on. There may be two or three. Factory wheels and a lot of aftermarket wheels have a small recess on the mounting surface on the back of the wheel around the the lug hole to clear the clips. (My Quadratec CJ Retro wheels have those and my '17 Chief still has the clips. The clips are removed once the rotors have been changed and no replaced.

If you have the clips and aftermarket wheels without the recess, then the wheel will not mount perfectly vertical on the hub and can cause a vibration. However, I don't think that is your issue.

Speed sensitive vibration, especially one that appears and then disappears in a 10 MPH range (typically, but not limited to 50 to 60 MPH is 99% of the time wheel/tire related. Most shops will not do a road force balance unless asked to do so, and many shops do not have the equipment to do it. The heavier the tire, the more critical the balance job is. The original tires on a Sport (not Sport S) were P225/75R16 tires (29") on steel wheels. If you have the aluminum wheels, then most likely you have 32" or larger tires.

If you have the steel wheels, it's easy to bump a curb hard enough to give the wheel a little wobble. I would have the tires re balanced, preferably at a shop that also does heavy truck tires. They have better equipment that will do the road force balance. Have them also check the wheel/tire for "runout" this is if the tire/wheel is out of round and also have them check the wheel for wobble.

What ever you do, until the wobble is fixed, try not to drive in that speed range, as it will damage the Jeep over time.
 

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Iris Wood Automotive wheel system Circle Rim
 

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Discussion Starter · #13 ·
Sorry all, I don't me to be naive-I was serious when I said I had no mechanical knowledge aside from changing the oil and an air filter (and a flat, I can do that!!). Not sure what this pictures means...should I be looking at my 4 tires and focus on the "arrowed" areas? Does this relate to somebody else's reply?
 

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The arrows are pointed at the two round springy retaining clips that would keep some wheels from resting flat against the rotor surface

Factory wheels have cutout to make room for those clips


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Sorry all, I don't me to be naive-I was serious when I said I had no mechanical knowledge aside from changing the oil and an air filter (and a flat, I can do that!!). Not sure what this pictures means...should I be looking at my 4 tires and focus on the "arrowed" areas? Does this relate to somebody else's reply?
No problem. As pointed out by the previous post. If you have non stock rims, those stars need to be removed. There are things i can't do either. No one is perfect....
 

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Discussion Starter · #16 ·
No problem. As pointed out by the previous post. If you have non stock rims, those stars need to be removed. There are things i can't do either. No one is perfect....
Gotcha, thanks. I'm running stock rims and the tires are not oversized at all R17s- they aren't huge off-road tires but they also aren't basic tires either.
 

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You have lots of help on the vibration. I will say to not rely on the computer for MPG info. I would give advise to forget about MPG with a Jeep. Its not an aerodynamic gas saver. Its a brick on wheels. If you are truly set on tracking then manually do it yourself by topping off and resetting your trip meter or just write down your current odometer reading. Then drive for your cycle, go to the gas station and top off and write your odometer reading. Then do the simple math. Current miles minus initial miles divided by number of gallons. Better advise is to just be at peace knowing whatever the mileage, thank God you are driving a Jeep.
 

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Discussion Starter · #18 ·
You have lots of help on the vibration. I will say to not rely on the computer for MPG info. I would give advise to forget about MPG with a Jeep. Its not an aerodynamic gas saver. Its a brick on wheels. If you are truly set on tracking then manually do it yourself by topping off and resetting your trip meter or just write down your current odometer reading. Then drive for your cycle, go to the gas station and top off and write your odometer reading. Then do the simple math. Current miles minus initial miles divided by number of gallons. Better advise is to just be at peace knowing whatever the mileage, thank God you are driving a Jeep.
Indeed, as much as I'm frustrated by the vibration (and feel the waning) I won't do anything drastic and get rid of it. Just can't throw money at it- chasing the issue (wife won't allow it) and I can't find a reputable mechanic with solid jeep knowledge. I hear you loud and clear on the mpgs- was just hoping to elminate anything else glaring that has changed since taking it over. Getting 240 miles on a tank I guess is what I'll live with- not that I'm disgusted by that- after all, it isn't a diesel VW. Thanks and thanks to all that have been so helpful. I've had more real suggestions and thoughts surronding this than the two mechanic's I've been to.
 

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Hang in there and you'll get it figured out with the help of these great members. I'm in the same boat after picking up an older model and have been spending time and money correcting what was wrong based on the help found here, not locally. The one thing I've come to grips with is although my new-to-me Jeep is green, it's not earth friendly eco-green! In fact, I would be ecstatic to see the nearly 16 MPH you're seeing...lol.
 

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To isolate it you might want to see if it does it only under acceleration through that speed,at steady speed or if it does it slowing down. Also you can get it to do it and pop it in neutral and see if it quits ( being careful of course) that will let you know if it is a issue under load or not. I would find a safe place get It where it smooths out and decelerate in and out of gear and see If it shimmies.
 
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