Help please...Is my drive line damaged? (1 Viewer)

[gpacho]

Hi all, need some technical advise from someone who understands differentials, transfer cases and transmissions on these trucks. I just picked up my first LC200, a 2013 with 100k miles. Super clean truck and I was very very excited.....unitl I discoved this!!
Tires were just upgraded from stock about 1000-1500 miles before I purchased it. 3 of 4 tires are BFG KO2 275/70/R18 BUT for some stupid reason the toyota dealer mounted a 285/65/R18 on the 4th wheel which is about 1/2" smaller in diameter (rear passanger side).
I've always carried a full size spare on other trucks as I've been told that running, even for a short while, with a different diameter tire from the rest can damage differentials and other drive line components. The previous owner did not notice that the dealer mismatched tire sizes and drove it for about 1000+ miles.
Can someone knowledgeable please share your thoughts on what damage if any may have occurred? And what else I should do besides changing diff/ trans case fliuds? It seems to drive normal but I'm worried that I've purchased a truck with compromised components. I've contacted the dealership responsible for the error but still waiting for a response.
Appreciate any guidance you all can provide.
Thanks

 

[bloc]

My tire shop did the reverse size mismatch (3x 285/65 1x 275/70) about 90k miles ago, I drove it for 700 miles mostly freeway before I noticed. They documented everything and basically insured my transfer case.. but it has had no noticeable effect whatsoever. And as stated, I’ve driven a long way since then.

 

[gpacho]

My tire shop did the reverse size mismatch (3x 285/65 1x 275/70) about 90k miles ago, I drove it for 700 miles mostly freeway before I noticed. They documented everything and basically insured my transfer case.. but it has had no noticeable effect whatsoever. And as stated, I’ve driven a long way since then.

thanks bloc! appreciate the response. Happy to read that it did not effect anything so far. I like the idea of requesting a warranty from the dealer. Hopefully they'll comply.

 

[rlynch356]

Differentials will turn at different rates, that is what they do...

I would
A) change the tire to the correct matching one
b) Change the gear oil just to be safe it's been working harder than normal..

You have 33.2" and 32.6" so the diff is making up the different rotational speed difference.. it also has not been driven thousands of miles... so the spider gears should be ok.. (that is what will fail)

Just change the one tire to the correct size as the others, it should be fine..

Added info: the transfer case is doing the same thing but the "load" is at the differential with the mis matched tires...

 

[vipergrhd]

I will give it a try so you get some idea what could fail and why, the posted distance seems not a whole lot to see any long term issue but I would check just to be sure. It doesn't matter if it's front or rear differential if one tire is smaller/bigger it will act like you are on a constant turn which could wear out your side gears and spider gears i have seen this failure but the size difference was about two inches or more and it chewed up both side gears and spider gears and destroyed the rest of the differential due to metal mixed in the gear oil. I will post videos so you get an idea what i am talking about, my suggestion is get a gear oil sample after getting the differential hot and send it for testing.

 

[TeCKis300]

Doing some math:

	285/65/R18	275/70R18	Delta	% Difference
Diameter	32.5"	33.2"	.7"	2.1%
Revs/mile	608	619	11	1.8%

Rear axle diff revs/mile difference: 11 revs
Front axle pinion output revs/mile: 619 * 3.9 = 2,414.1 revs/mile
Rear axle pinion output revs/mile: (619+608)/2 * 3.9 = 2,392.65 revs/mile
Center diff delta: 21.45 revs/mile
Center diff % difference: 0.9%

I would have no concern to the rear open differential. Managing 11 revs or 2.1% difference in the spider gears is in the noise with no appreciable load/heat.

The center diff, being a torsion diff may see slightly more load. Fortunately the rear diff would have averaged some of the difference. The center diff does turn at a higher speed so it sees more revs/miles difference, but the difference is less than 1%.

From what I've read and have experienced with other AWD cars, with staggered tires, a difference of less than 3% revs/mile is okay. This is under. With how robust the 200-series driveline is, I wouldn't sweat it.

I like @vipergrhd recommendation if you want piece of mind. I wouldn't bother with the rear diff. Transfer case / torsion diff may be worthwhile to change and sample the fluid on.

 

[bloc]

Differentials will turn at different rates, that is what they do...

I would
A) change the tire to the correct matching one
b) Change the gear oil just to be safe it's been working harder than normal..

You have 33.2" and 32.6" so the diff is making up the different rotational speed difference.. it also has not been driven thousands of miles... so the spider gears should be ok.. (that is what will fail)

Just change the one tire to the correct size as the others, it should be fine..

Added info: the transfer case is doing the same thing but the "load" is at the differential with the mis matched tires...

Since the center diff is the only one that is limited slip it is actually seeing the most “load” in this scenario.

The axle with matching tires will just see a bit more torque, as if towing a trailer or something (though I’d guess far less torque here than towing.) The axle with mismatched tires will see the greatest speed differential, but it isn’t generating significant friction.. it’s the torsen in the center diff creating friction to induce the limited slip effect.

The nice thing about this scenario is with only one tire slightly smaller, the speed delta at the center diff is only half of what it would be if say one axle had the smaller tires. Or put another way, your 1/2” smaller single tire only looks like 1/4” smaller on one axle.. and that’s a negligible difference out of 32”, especially for a drivetrain as robust as ours.

Yes to have total peace of mind you can send off gear oil for analysis.. especially if the dealer will pay for it. But without unit averages for our cases to compare your data to it’s hard to know what is acceptable wear and what may have been caused by this incident.

 

[gpacho]

I'm new to this forumn and the LC community. Wasn't sure I'd even get a response... BUT WOW!! YOU GUYS ARE AWESOME!! Thanks for taking the time to share your knowledge and give me some peace of mind. I'll be swapping the tire today to the correct size and will try to get the fluids analyzed. I'll be sleeping much better tonight! Thanks again @bloc, @TeCKis300 , @vipergrhd and @rlynch356. Much appreciated!

 

[rlynch356]

FWIW… changing the fluids in the front and rear diffs is easy for a DIY project.
Same with the transfer case but it has a lot more bolts up come off for the guard.
Drain into a clean oil drain pan, and then use a magnet to see if there is any metal shavings in the old fluid. A very little is normal, a lot is not and you have a problem.

I use redline oils

Red Line Synthetic Oil

Red Line has a reputation with racers and enthusiasts alike for creating products that perform and protect better than any on the market. No compromises.

www.redlineoil.com