Driving with one smaller tire for a long time: what could happen?

[sshanky]

Hi,

My 2000 Mountaineer AWD V8 has been leaning slightly to the left for a while. I thought it was just something in the parking lot, or perhaps something wrong with a suspension component. But I never suspected tire size, since Discount Tire sold me 4 new 235/75R15's in late 2011.

The other day, while having it serviced, I asked the mechanic to see if I'm right and the car is really leaning over, or if it is my imagination. He found that one of the tires was actually a 225/70R15, same brand and model, which I know is substantially smaller. I couldn't believe I hadn't noticed that before.

I am wondering what potential damage this could cause to the car. Something did happen to the car following the installation of the tires, but I don't want to taint the discussion yet -- I want to know what risks there are with one tire being that much smaller than the rest.

Thank you for your input!

 

[Glen4X4]

Being that you are AWD it could cause binding in the system and damage the front differential and/or the transfercase its self..

 

[koda2000]

you can ruin the viscous coupling in the transfer case. driving with tires that are not very close to the same diameter with AWD is a no-no.

 

[sshanky]

Thanks guys, that's what I had suspected...because that is what happened. On a trip from Phoenix to Flagstaff, the front transfer case/differential (not sure what it is called) blew up and poured oil all over the highway, and the car wouldn't move.

We temporarily disconnected the front end by removing the axles and transfer case and now the car is working fine (although it drifts downhill imperceptibly slowly when left in park without parking brake applied -- like a few feet in hours).

I filed a claim with Discount, and they are going to have an adjuster come and meet us. I wonder what they should be responsible for, having put the wrong size tire on. We went there yesterday, ended up buying some new tires, since the old ones were so worn after three years, and they told us they were submitting the claim for us.

Thanks for the replies...

 

[obie]

The downhill drift is because the transmission parks through the transfer case front output. With no driveshaft or working front axle, the transmission can't actually park. Does your parking brake work? If so, you should apply it every time you park, otherwise if your truck hits something you're responsible.

Make sure that you claim transfer case damage (or at least make sure they thoroughly inspect the transfer case before the final claim) through Discount Tire, as your viscous coupler is very, very likely ruined if the front differential exploded as well. That's $300 minimum for the part and likely another few hundred if not thousand to have the transfer case rebuilt by a shop.

 

[Glen4X4]

DO NOT REMOVE the Axles! Removing the front axle shafts can be fatal on these trucks, they help keep the wheel bearing stable, without that the wheel bearing can fail and cause your wheel to fly off while driving, literally. If you're going to continue driving it, put the axle shafts back in and make sure your differential is full of gear oil. If you must drive without AWD then only remove the front driveshaft and be sure the parking brake is in good working order.

 

[SoNic67]

You already did more damage to AWD by removing the front shaft.
The adjuster will now probably not cover anymore the central differential (that contains the viscous coupling) because of that.

As for the front axles - you are suicidal probably... Your wheels can fly off the truck - that happened already to another guy on this forum.

 

[obie]

Not telling the guy this is safe for sure, but I don't think his wheels will fly off. With the 4WD and AWD Explorers, the front uses unitized hub bearings. These are sealed and independent units already set with preload and bolted to the steering knuckle. The only function of the CV as far as the hub is concerned is to spline through it.

In this case, the CV shaft and axle nut aren't providing the preload and clamping force on the separate inner and outer wheel bearings and races.

If the hubs weren't put back on correctly then yes, his wheels will fly off. But if the hub is torqued to the knuckle, and the wheel torqued to the hub, then I don't see any reason the wheel should fly off.


That all said, the best thing to do would be to cut each CV shaft so the outer shaft and spline is usable, then run it back through the hub and torque it down again. Try to get new axle nuts if you can, as the nuts are a prevailing torque nut and should never be reused.

Edit: Oh, I should add though that running without CV axles installed, even if it's safe (again, I'm not 100% sure about this, should only ever be a TEMPORARY thing. Even if they don't fly apart, you're still leaving a gaping hole on your wheel hub and that means it's really easy to get dirt and debris in there and damage it. And if something gets in there and locks the hub up, well, you're in for a very bad day.

 

[tenny]

Not telling the guy this is safe for sure, but I don't think his wheels will fly off. With the 4WD and AWD Explorers, the front uses unitized hub bearings. These are sealed and independent units already set with preload and bolted to the steering knuckle. The only function of the CV as far as the hub is concerned is to spline through it.

In this case, the CV shaft and axle nut aren't providing the preload and clamping force on the separate inner and outer wheel bearings and races.
If the hubs weren't put back on correctly then yes, his wheels will fly off. But if the hub is torqued to the knuckle, and the wheel torqued to the hub, then I don't see any reason the wheel should fly off.


That all said, the best thing to do would be to cut each CV shaft so the outer shaft and spline is usable, then run it back through the hub and torque it down again. Try to get new axle nuts if you can, as the nuts are a prevailing torque nut and should never be reused.

Edit: Oh, I should add though that running without CV axles installed, even if it's safe (again, I'm not 100% sure about this, should only ever be a TEMPORARY thing. Even if they don't fly apart, you're still leaving a gaping hole on your wheel hub and that means it's really easy to get dirt and debris in there and damage it. And if something gets in there and locks the hub up, well, you're in for a very bad day.

everything you said is somewhat correct...what I highlighted is NOT TRUE...

that bearings integrity DEPENDS ON the torque of the axle nut....without
the splined shaft and nut, your wheel CAN AND WILL "FLY OFF" under
the right conditions....

I for one, wouldn't want to test those conditions.....

these bearings can be EASILY pulled apart with a slap/slide hammer.
(I do this on a regular basis) they are only pressed in at the races
with a small coupler (that the axle actually runs through).

please ....if anything take apart the axle, and put the spline end
back into the hub and torque the nut back down.

 

[obie]

I didn't know that, thanks. I've never tried tearing one apart; I didn't realize how easily they could be disassembled.

 

[Robman]

Scary stuff ! ... on a side note, I reuse those nuts and also the caliper bolts and haven't had any issues on any of my 3 explorers... well 2 explorers .. I scrapped my XLT today after stripping it down darn near completely.. a shame because the body was excellent and the SOHC motor ran perfect, damn transmission. My 4.0L OHV 5-spd manual sport hauled it on a car trailer like a champ, the whole shebang weighed 9000 lbs, the stripped explorer weighed 2800lbs.

 

[tenny]

Scary stuff ! ... on a side note, I reuse those nuts and also the caliper bolts and haven't had any issues on any of my 3 explorers... well 2 explorers .. I scrapped my XLT today after stripping it down darn near completely.. a shame because the body was excellent and the SOHC motor ran perfect, damn transmission. My 4.0L OHV 5-spd manual sport hauled it on a car trailer like a champ, the whole shebang weighed 9000 lbs, the stripped explorer weighed 2800lbs.

the nuts can ABSOLUTELY be re-used....so can caliper bolts....

I have reused literaly HUNDREDS of both of these nuts and bolts,
and never had any failures of ANY kind...

of course this is only my experience (25 years) and I am Toyota dealer
trained the first 8 years of my career, and have never herd of using
new axle nuts....hhmmmmm..

now, of course if you replace an axle.....you absolutely use the NEW
hardware, and always use new hardware with new parts..yadayadayada...

my 2 cents

 

[sshanky]

Now you guys have me worried

The new transfer case/differential would have cost a grand, and the car has 150k miles on it, so we wanted to try making it rear wheel drive only, thinking that, here in AZ, there's not much need for AWD. Plus, we figured we could save a lot by not buying the new parts.

The first time it was repaired, right after pulling out onto the street, the wheel fell off. The mechanic was probably going nuts with guilt and worried to death -- lucky it happened right away, and he could fix it, which he did, and he claimed it would never fall off after that. I assume he figured out the mounting procedure and did it correctly. The car has been in the same condition for two years with no issues, but I fear based on what you all have been saying that we might have just been really lucky. I am worried about driving it now.

Unfortunately, I suspect the parts are gone, and there is no way to replace the axles without purchasing new ones. I will wait until the Discount Tire adjuster calls me, and perhaps find a lawyer!

Meanwhile, do you think I should stop driving it? I took a look behind the wheels and noted that there is no axle, but I didn't quite see a hole leading into the bearings.

I'm so upset that this was all caused by Discount's negligence!

Thanks to all of you for your help and input.

 

[Glen4X4]

With your truck being on stock size tires the dangers aren't as high as us with over size tires but I honestly wouldn't be using it as a daily driver without it being in its proper setup. There are guys that have made stub axles just so they can drive their 4wd without worry of the bearing failing. Its your choice but I'm honestly telling you that I wouldn't with knowing what I know.

 

[SoNic67]

Scenario:

The bearing will probably blew apart when you are doing 70mph on highway. Front end will drop and dig into concrete. Brake line will broke bleed all fluid, so no brakes. You have a good chance to flip-over.

Your choice.

See here for a lucky example:
http://www.explorerforum.com/forums/showthread.php?t=381017

i had the cv joint disconnected from the hub but at this point i couldnt feel my hands so my dumb ignorant self was like hey its gonna be nice out tomorrow lets just bolt it back up and leave the cv joint disconnnected from the hub, no big deal as long as my rear doesnt slip and dont go into 4x4, boy was i wrong.... so the next day im about 10 miles from my house when i heard clicking then bam the front left tire and wheel shot out from under me and went bouncing in the rearview to god knows where and it also ripped the brake cable and caliper away with the rotor wheel and tire, so it bled all the brake fluid out at 75 mph so i had to wait for it to grind to a halt