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  #1  
Old April 12th, 2013, 03:22 AM
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David
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Do you confirm?

Recently I have noticed a new issue with my D90. Ive given it a lot of thought and what feed back as to if anyone confirms my disagnosis.

This is the symptom: at highway speed my D has a reocurring vibration(s), meaning that every 1.5 to 2 seconds there is a vibration that comes from everywhere. Its a quite intense vibration- no noise, no banging. The vibrations start as quickly as they stop in an on again off again manner. On for approximatly 1.5 to 2 seconds, off for 1.5 to 2 seconds... and over and over. Its like a sin wave its its perfect repetition. This happens on straight highway (I dont know about curved roadway as we dont get much curved highway here in CA)

I thought long and hard about this. The on and off manner of the vibration leads me to eleminate:
Out of Balance wheel(s)
Loose fan blade
Misfiring cylinder
Off balance engine parts
Bad CVJ (or what ever they are called on the Defender)
and
Mud in the tires

I was really stuck on how perfectly spaced each interval of vibrations was from the next set of vibrations. Too far apart to be something spinning at normal engine speeds, but spaced so exactly apart it had to be SOMETHING spinning.

After a week of this issue, while doing some other maintainance I realized that my rear tires are 285s and my front tires are 265s.

So here is my theroy: the rear axle/wheels/diff is turing just a little slower than the front axle/wheels/diff. Every 1.5 to 2 seconds the different rotation speeds clash somewhere (I assume in the trans case or manual box) causing the grears/tranie/body to vibrate in a perfectly spaced rythum.

Do you confirm with my theroy? Thank you for your time in advance.
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  #2  
Old April 12th, 2013, 03:31 AM
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You need to buy matching tires today, your gonna kill your driveline. I guess you do realize this truck is fulltime 4wd, do you have the owners manual?
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  #3  
Old April 12th, 2013, 06:13 AM
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Quote:
Originally Posted by rover4x4 View Post
You need to buy matching tires today, your gonna kill your driveline.
Absolutely. Stop driving your truck until you have matching tires.
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  #4  
Old April 12th, 2013, 07:59 AM
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Dennis Lynch
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Wow. That sucks, unless you were looking for an excuse to buy bigger tires....
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  #5  
Old April 12th, 2013, 08:11 AM
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Mike Hammond
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The centre diff will have been working overtime
For piece of mind I'd change the transfer box oil. Hopefully the magnetic drain plug won't look like an oily Christmas tree made from metal filings.
Check and grease the UJs on the drive shafts and grease the sliders on the prop shafts after checking them too.
Get a set of matching tyres and like everyone else has said don't drive it until the tyres are a matching set!

Worst case is the centre diff in the transfer box fails big time ( if it isn't on it's way out already.) The planet gears are very enclosed in the centre diff and the diff isn't designed to run for long periods with the front /rear props rotating at different speeds.
Is the truck new to you?
How far/long have you been driving the truck like that?
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  #6  
Old April 12th, 2013, 11:47 AM
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It's not the 285 vs 265 that's the issue it's the tire height/ circumference that's the real issue. THAT'S the real issue.

I found this out when after I installed my Detroit in the rear & the tire circumferences were off by 1". So about every 1/4 mile, the locker would "bang" and release the wind-up, and of course the rear would shift slightly sideways. Not fun at 65 mph.

I have read that the "cheeze-ball" way around this issue is tire inflation. Under inflate the "tall" tire & over inflate the "short" tire (changes the circumference).
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  #7  
Old April 12th, 2013, 02:13 PM
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Quote:
Originally Posted by Dennis View Post
It's not the 285 vs 265 that's the issue it's the tire height/ circumference that's the real issue. THAT'S the real issue.
The rolling circumference needs to be the same. I very much doubt the aspect ratio will be matched.
265/ 65 R 16? and probably 285/65 R16?
What does it say on the tyre wall David?

I'm not even sure reducing the pressure affects the rolling circumference, the same tread has to turn and be in contact with the road. I'd be interested to find out.
Underinflation will lead to bad handling at best, overheated and blown tyres at the worst, with poor fuel consumption and a high wear rate in between.

Ever tried to corner on a blown rear? Massive understeer! Had a ring side seat once when a car blew a rear tyre on the M23 took all 3 lanes and the offside crash barrier for the driver to not regain control.
Correctly sized tyres is what's needed before the diff blows ( if it's not on it's way out already).
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  #8  
Old April 12th, 2013, 02:28 PM
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Mike Hammond
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Quote:
Originally Posted by Dennis View Post
I found this out when after I installed my Detroit in the rear & the tire circumferences were off by 1". So about every 1/4 mile, the locker would "bang" and release the wind-up, and of course the rear would shift slightly sideways. Not fun at 65 mph.
Out of curiosity were your mis matched tyres on the rear axle? Was this due to wear or incorrectly matched tyres?
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  #9  
Old April 12th, 2013, 06:24 PM
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David
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I ended up witht these tries becuase im broke an can not afford new tires. It was mismatched before as the old owner had Continentals on the front and Mich on the rear (the spare is a Bridgestone). And those tires were over 12 years old.

One of the Mich cracked on the side wall from age I had to get some used tires. They didnt have 265s they only had 285s that day. So I got what they had @ the used lot.

So is it any harm if I go up to 285 on the front so I have 4 tires all the same size?
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  #10  
Old April 12th, 2013, 06:31 PM
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Chris
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This thread is useless without pics
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  #11  
Old April 12th, 2013, 11:02 PM
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Quote:
Originally Posted by mikeslandrover View Post
Out of curiosity were your mis matched tyres on the rear axle? Was this due to wear or incorrectly matched tyres?
I had 1 original spare tire, BFG AT/KO 235/85-16", had never been used. I decided to rotate in it & only buy 3 new tires and save one of the worn ones to be a spare. These were BFG AT/KO 235/85-16's. The 3 new units did not have the same circumference as the older unit. They were manufactured about 4 years apart. So yes, I ended up with an old and a new tire on the rear axle.

Solved problem by rotating new/old tire to front axle. Since the front axle wheel turns at differing speeds while cornering, the front open diff compensates for the 2 different turning radii of any given corner, hence problem solved.

I buy tires in sets of 4, now that I have a worn tire as a spare, and haven't had that problem since.
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  #12  
Old April 13th, 2013, 02:17 PM
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Mike Hammond
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Quote:
Originally Posted by mikeslandrover View Post
Ever tried to corner on a blown rear? Massive understeer! Had a ring side seat once when a car blew a rear tyre on the M23 took all 3 lanes and the offside crash barrier for the driver to not regain control.
Correctly sized tyres is what's needed before the diff blows ( if it's not on it's way out already).
I did of course mean oversteer not understeer

Anyway David, 285's will be fine on all four corners as long as the aspect ratio, the second number on the tyre wall, is the same.
You might get slightly less acceleration and restrict your turning circle with 285's.

Full explanation of tyre wall codes:-
http://www.jaxquickfit.com.au/tyres/...e-numbers-mean

------ Follow up post added April 13th, 2013 07:20 PM ------

Quote:
Originally Posted by Dennis View Post
I had 1 original spare tire, BFG AT/KO 235/85-16", had never been used. I decided to rotate in it & only buy 3 new tires and save one of the worn ones to be a spare. These were BFG AT/KO 235/85-16's. The 3 new units did not have the same circumference as the older unit. They were manufactured about 4 years apart. So yes, I ended up with an old and a new tire on the rear axle.

Solved problem by rotating new/old tire to front axle. Since the front axle wheel turns at differing speeds while cornering, the front open diff compensates for the 2 different turning radii of any given corner, hence problem solved.

I buy tires in sets of 4, now that I have a worn tire as a spare, and haven't had that problem since.
Thought that would be the case.
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  #13  
Old April 13th, 2013, 05:25 PM
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Quote:
Originally Posted by petminded View Post
I ended up witht these tries becuase im broke an can not afford new tires.
Perhaps a Land Rover isn't the best car to drive if you cant even afford tires...

Quote:
Originally Posted by petminded View Post
So is it any harm if I go up to 285 on the front so I have 4 tires all the same size?
I would be cautious when mixing different brands too; they can be like shoe sizes.
One manufactures "285" may not be quite the same as another's.
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  #14  
Old April 13th, 2013, 05:55 PM
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Not to be ugly here but my 11 year old daughter asked what was so funny when I was chuckling reading Jeff's post. So I gave her a summary of the OP's question and asked her if she would ever put different sized tires on a truck. She just looked at me and said "don't be silly daddy, thats just awkward." Just sayin'.
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  #15  
Old April 13th, 2013, 06:19 PM
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Mike Hammond
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Be nice, he's learning. Land Rovers can be a steep learning curve.
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  #16  
Old April 13th, 2013, 06:44 PM
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Raub A.
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I know I know, just a little humor. My first truck was a series IIa, it was a good learning vehicle - replaced the frame, the motor, half shafts, and the brake master and slave cylinders. Then had to rebuild them twice untill I figured the brake fluid I was using was eating the rubber up - D'ho That is why I went with an ExMoD they seem a little simpler than an NAS (not that I could afford one) which is good for my limited mechanical abilities.

On a serious note did anyone mention the NAS oil line issue?
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  #17  
Old April 14th, 2013, 12:09 PM
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Phillip
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Quote:
Originally Posted by Nomar View Post
Perhaps a Land Rover isn't the best car to drive if you cant even afford tires...



I would be cautious when mixing different brands too; they can be like shoe sizes.
One manufactures "285" may not be quite the same as another's.
Absolutely, if you can't afford tired sell the truck. There is no reason that this thread should be this long.

Please don't post when your transfer case is shot
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  #18  
Old April 14th, 2013, 02:34 PM
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Quote:
Originally Posted by rover4x4 View Post
Absolutely, if you can't afford tires sell the truck. There is no reason that this thread should be this long.

Please don't post when your transfer case is shot
Post away David, I'll talk you through a transfer box change.

Had to change the transfer box myself once on the way back from Morocco.
Five hours from wheels stopped to wheels rolling again.
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  #19  
Old April 14th, 2013, 05:15 PM
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Quote:
Originally Posted by rover4x4 View Post

Please don't post when your transfer case is shot

LOL

And don't post for info on how to convert you 90 to 2WD because you're broke and can't swap a $300 LT230 out...


The transfer gears are pretty stout in harsh conditions; there's a member here who drove from WV to VA with a teaspoon of gear oil in the case.
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  #20  
Old April 14th, 2013, 05:53 PM
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Lock center diff and pull front drive shaft.
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