Rotating Tires and 4 Wheel Drive

Dear Click and Clack,

My handsome prince, proactively rotated the tires on our 1997 Chevy Suburban with push button four wheel drive. We started getting a funny grinding noise up front immediately following the rotation. Realizing it was beyond our capabilities, we went directly to a trusted mechanic who decided we needed an expert transmission diagnosis. Thinking it had to be computer related to the tires, we thought it would be best to go to the dealer,upon which time the fuel pump went out. We had it towed to the dealer. The dealer was unable to get a computer reading on the drive train computer, TCCM, sensors without $800 for the fuel pump replacement, so we had it towed home. My handsome prince replaced the pump and it is working great. We are back where we started, sort of, and wondering how to fix the original problem of the 2 and 4 wheel drive. The 4 wheel hi and lo lights will blink and come on/off when we attempt to engage the 2 wheel option. Any suggestions? Thanks for your time and thoughts on the situation

Are the front and back tires the same tire in the same size? Is there a big difference in the tread on the front and back tires at this point?

This. To explain: differences in tire diameter can ruin differentials, as one side will be turning at a different speed all the time instead of just some of the time. If this uses a viscous coupling for the center, possibly some other types of center differential, you could be looking at a new diff, and more frequent tire rotations in the future.

It is the same tire, in the same size with no noticeable tread differences at this point. The tires are E rated and about a year old.

What does your owner’s manual say on this subject? I believe you will find they say you need tyres matched with within a maximum difference. You can have the larger tyre(s) shaved down to the same size as the other tyres.

All the tires are the same size and within manual limits.

Just a hunch, does the truck have automatic locking hubs? And did the weather get much cooler immediately after the tire rotation? Automatic locking hubs are prone to drag when the grease is cold and thickens.

Assuming no unicorns, the physical tire rotation is out of the loop for cause. There’s no OEM engineered 4x4 with different sized tires front to rear …and certainly not a Suburban. That reduces any differences in tires front to rear to marginal/fractional.

Now if Prince Valliant disturbed a wheel speed sensor while doing it …that could be another issue, but I’d expect a CEL for ABS

This sounds like the magic words, but the wrong language for me. Is there a good wizard or link that could direct me more on the repair? Should I let him back under here…especially in this cold weather, or try a different dealer/mechanic?

Have you checked the easy stuff? Whenever you do a service and something new crops up, it’s always best to check your work to make sure it’s not caused by the most recent service. Case in point; did you chock the rear wheels and jack up each front side, rotate the wheel and check for the source of the noise? It could be something as simple as a bent backing plate rubbing on the rotor…

Yes, did that, but it seems like the transfer case is stuck between 2 wheel and 4 wheel drive, and it doesn’t know which one it is in…

Maybe I did not make myself clear. Were you measuring the circumference of the tyre, or were you looking at the measurements of a new tyre of the size on your car?

If they do have the same circumference, you are good to go.

All of the tires have the same circumference per the number on the tire and physical measuring.

I assume you tried just backing the truck up to unlock the drive. If not try it for several feet

Yes…we did try that. Any other ideas…please?

Are the wheels identical? Do they have the same profile inside, on the side that faces the axle? I’m thinking maybe it’s rubbing on the brakes. Unlikely but who knows at this point. Well, that could cause a sound.

Otherwise, it’s coincidence. No connection between rotating the tires and your 4WD problem.

Yes, we have automatic locking hubs. The weather got colder about 2 weeks after the rotation, but the grinding started immediately after the rotation. Would this cause the 2 wheel and 4 wheel hi/lo indicator lights to not indicate, too, or do you have a suggestion on how to check this out?

If the indicator lights are blinking then there is a problem witht the 4wd system. The system can be accessed with a scanner to see what codes are stored. Once the codes are accessed you will have a better idea of what needs to be done next.

If have a AUTOZONE close by you can stop in there to have them access the codes.

The Autozone code reader can only access the check engine light codes, not the 4 wheel drive system. There must be a separate code reader for the 4 wheel drive. The friendly tow truck driver who has been getting us around town said it is a proprietary code reader at the dealers for the 4 wheel drive, but the dealer we went to was not able read the 4 wheel drive code without the $800 fuel pump repair, which sounded suspicious to us…

If autozone can’t get into the system then your other choice might be to bring it to the dealer.

I can’t believe they wouldn’t pull the codes unless you did the fuel pump, that’s a load of crap. They should be able to pull the codes now that the fuel pump has been replaced.