Dammit! I got a nail in one of my tires at 27k miels and replaced two of them, not knowing that this stresses the differential unless you replace all four.

Anyway, that was 7k miles ago. Last week I decided to check my rear differential fluid level as I changed it at 30k miles (3k miles ago). It was fairly black, certainly not the darker golden brown I had when I changed it at 30k miles.

I measured the circumfrence of my tires on both sides front to rear. Left side had a 1/2" difference and the right side a 3/4" difference! DOH!

So, I now have four new tires on order and so far I have not noticed any fference in performance or any starnge noises. Has anyone here had an experience like this? Is the differential something that would just blow up and fail or did I do some damage to it that will show up in terms of longevity?

signed
Dumb and dumber

Probably wouldn't destroy your diff but unless you sustained really high speeds then I don't think it will be an issue. Diffs have to work anyways because cars turn... it just is making the diff work overtime since the tire diameter was off for a period of time. Obviously this would have been exaggerated if you sustained really high speeds (did you!?) since the diff would have to make this compensation at a more rapid pace based on your speed... but if you ran mismatched tires around town for a couple thousand you probably didn't damage your diff too much. Either way just don't do it again and I'm sure you'll be fine. Diffs usually wear out and don't fail catastrophically.

Oh and it was good that you caught yourself before it was much longer... and at least the fluid was fresh...

Unfortunately, a good 6k of those 7k miles were highway speeds commuting to work. I plan to change the fluid again after I have the new tires installed.
Thanks for the advice.

Like I said, no unusual sounds but I do have the smell of gear oil coming from my engine bay where I spilled some gear oil on my intercooler while changing the transmission fluid. It was only a gulp or two before I uprighted it but I have sprayed it with low pressure water mixed with simple green and it still doesnt seem to get much better. I havent noticed any smoke so hopefully the front differential is not burning up. The fluid in the front diff. looks as good as the day I put it in.

y not just patch or plug the tire? i ran over a 1/2" x 5" bolt. plug it up!

I had it plugged three times but it didn't hold so I ended up having to replace it.
The hole was very close to the sidewall and the plug just wouldnt last more than a few days before it started leaking again.

did you put the two new tires on one side only? Under normal driving your front should always wear out faster than your rear, which is okay... I try to rotate mine every time I do old change.

No, I put the new pair on the front and left the old pair on the rear. I have rotated them twice since then as I rotate mine with every oil change but I do front to rear.

hmmm... if that is the case, you should be okay. if anything is over worked, it would be your center diff. Which shares fluid with the tranny. That shouldn't affect your rear diff. fluid. BTW, you should always move the tires with more tread to the front, not just rotate. Just remember to pay attention to the tire tread pattern. Some can not be cross rotate (uni-directional).

No, I put the new pair on the front and left the old pair on the rear. I have rotated them twice since then as I rotate mine with every oil change but I do front to rear.

Well I got all four tires on and everything seems to be OK. I guess I dodged a bullet on this one. Even though there were differences between the circumfrence of the frt and rear tires nothing showed up in the 6-7k miles I drove it. No unusual sounds or anything like that. Surely something would have shown up in 7k miles...heck, 1k of those miles was spent towing a trailer through East TN hills!

Changed the rear diff fluids today and it was OK. The frt differential fluid still looks like honey.

<whew!>

hmmm... if that is the case, you should be okay. if anything is over worked, it would be your center diff. Which shares fluid with the tranny. That shouldn't affect your rear diff. fluid. BTW, you should always move the tires with more tread to the front, not just rotate. Just remember to pay attention to the tire tread pattern. Some can not be cross rotate (uni-directional).

you can rotate directional tires, you just have to take them off the wheel to do it. it's the asymmetrical ones that you can't rotate.