AWD Jeep...blow 1 tire, replace all 4
03-03-2009, 08:19 AM
#12
Ok I'll try and make this simple.
Any differential has a certain degree of 'looseness' often referred to as lash.
Too tight and the diff will wear out very quickly.
Because of the lash there is a slight delay in power being delivered to any specific wheel.
The power delivery can cause a slight rebound into the driveline.
now think about the fact that there are 2 diffs in an AWD system.
power hits the first diff and gets split into the front and rear diffs and then out to the wheels.
If one of the loads i.e. wheels, accepts power at a different level due to size it will result in a different magnitude power reflection.
Now Drivelines are dynamic systems so at particular frequencies
they can be prone to oscillating.
the introduction of an imbalance creates two harmonic frequencies in the system.
When you add two harmonics i.e. sine waves Sin(a) + Sin(b) you get a third harmonic wave which is the difference in frequency between the a and b.
This resulting harmonic can be a couple of Hertz or at a range of 30 or 40 hz.
In the upper ranges you easily hear it.
If the range is at the harmonic ofthe tire sidewal it will chew the crap out of the tire in short order.
as the tire wears it will also reinforce the harmonic difference which makes it worse as makes it wear even faster.
Any differential has a certain degree of 'looseness' often referred to as lash.
Too tight and the diff will wear out very quickly.
Because of the lash there is a slight delay in power being delivered to any specific wheel.
The power delivery can cause a slight rebound into the driveline.
now think about the fact that there are 2 diffs in an AWD system.
power hits the first diff and gets split into the front and rear diffs and then out to the wheels.
If one of the loads i.e. wheels, accepts power at a different level due to size it will result in a different magnitude power reflection.
Now Drivelines are dynamic systems so at particular frequencies
they can be prone to oscillating.
the introduction of an imbalance creates two harmonic frequencies in the system.
When you add two harmonics i.e. sine waves Sin(a) + Sin(b) you get a third harmonic wave which is the difference in frequency between the a and b.
This resulting harmonic can be a couple of Hertz or at a range of 30 or 40 hz.
In the upper ranges you easily hear it.
If the range is at the harmonic ofthe tire sidewal it will chew the crap out of the tire in short order.
as the tire wears it will also reinforce the harmonic difference which makes it worse as makes it wear even faster.
03-03-2009, 05:56 PM
#13
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Alot of AWD suvs and cars have to replace two tires so you have the same tread pattern on the same axle, But some vehicles you do have to replace all four, the jeep you act. do. It can very easily ruin the transfer case if not.
03-03-2009, 06:28 PM
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I know, a kid that used to work with me he wasnt a mechanic just did tires and oil changes and batterys, easy stuff put a wrong size tire on a back of a subaru, awd and blew the transfer case.... key words used to work with me ha
03-03-2009, 06:59 PM
#16
as I think back on this , last summer my kid had a blowout with my E430.
put the spare on which was new vs snows which were at end of life.
All the way to tire place I could hear the wowawowawow in the driveline.
put the spare on which was new vs snows which were at end of life.
All the way to tire place I could hear the wowawowawow in the driveline.
03-03-2009, 08:09 PM
#17
Remeber folks, its not just me. Obama wants you to crush your SUV. Lainey and Steve, 
DO WHAT YOUR PRESIDENT TELLS YOU.
From 60 minutes:
Kroft: When the price of oil was at $147 a barrel, there were a lot of spirited and profitable discussions that were held on energy independence. Now you've got the price of oil under $60.
Mr. Obama: Well, because this has been our pattern. We go from shock to trance. You know, oil prices go up, gas prices at the pump go up, everybody goes into a flurry of activity. And then the prices go back down and suddenly we act like it's not important, and we start, you know filling up our SUVs again.
And, as a consequence, we never make any progress. It's part of the addiction, all right. That has to be broken. Now is the time to break it.
DO WHAT YOUR PRESIDENT TELLS YOU.From 60 minutes:
Kroft: When the price of oil was at $147 a barrel, there were a lot of spirited and profitable discussions that were held on energy independence. Now you've got the price of oil under $60.
Mr. Obama: Well, because this has been our pattern. We go from shock to trance. You know, oil prices go up, gas prices at the pump go up, everybody goes into a flurry of activity. And then the prices go back down and suddenly we act like it's not important, and we start, you know filling up our SUVs again.
And, as a consequence, we never make any progress. It's part of the addiction, all right. That has to be broken. Now is the time to break it.
03-03-2009, 11:00 PM
#18
My friend's mother's just learn the cold truth about this with her Murano. They told her that some of the safety system whould not work properly due to the sensor is detecting a difference in the tires.
03-03-2009, 11:41 PM
#19
The tires on the 06 Jeep (don't know the mileage) must be worn enough that a good match can't be made. If money is tight put the new tire on the main drive wheel, or better yet replace the 2 on the same axel, with summer coming the awd might not be needed much. Replace all by next winter.
03-04-2009, 03:31 AM
#20
ah bill you are confusing AWD and SUV's.
my E and S are both sedans but are AWD.
my E and S are both sedans but are AWD.