This one got me stumped! awd question

[jeremy97]

Hey i got maybe a stupid question here but i just got some new "used" tires today for my 97 awd drive explorer. I noticed that when i am accelerating there seems to be a hop. Is this my awd kicking in or is it something mechanically not pertaining to my awd? Thanks!

 

[joecrna]

The AWD is always engaged. All 4 tires must be the same diameter or drive train parts will fail soon.

 

[Joe Dirt]

What drivetrain do you have? V8 AWD? V6? If you have a V6, what does the knob on the dash say above it?

 

[RomeovilleIL]

If you have an AWD with limited slip, that hop may be the rear locking up due to rotation differences. On the AWD models (not 4x4) all the tires must be very close to the same diameter. The limited slip mandates both rears be identical size. On the front, you can have 2/32" max total deviation from the rears since it has an open carrier. If all the tires are all the same brand and model then using a depth guage to measure tread depth provide a valid comparison. If the tires are different models it will be more challenging to get accurate measurements since the allowable deviation is so small.

After you make the measurements, get 2 same sized tires on the rears & put any off sized on the front. If you have one tire which is particularly larger, a decent tire shop can shave it down. If one is much smaller, you would probably be best served going back and trading for a closer sized one rather than turning down 3 to match the set.

 

[SoNic67]

The center differential on AWD is limited slip too, so between front and rear should not be any difference.
User manual says that all tires shold be identical.

 

[RomeovilleIL]

The center differential on AWD is limited slip too, so between front and rear should not be any difference.
User manual says that all tires shold be identical.

I got my info from Ford after destroying a tire offroad in Colorado during elk season last month. I had put a full new set of Toyo OC AT 30x9.5r15's on back on June and had around 6k miles on them at the time.

Started with brief discussion with the local shop of how it's really okay not to have standard 235x75r15's on an explorer. Choices given since they did not carry the same brand was get a new full set or shave down all 3 to match the goodyear model they carried which was about 7/32" smaller diameter. I wasn't real keen on having nearly half the tread shaved off my new tires nor with scrapping them so decided to try another shop for a second opinion.

After all said and done found a shop that had a new Toyo to replace it. Headache was the new one had 17/32" tread while three remaining tires measured 15/32" tread depth. Of course they did not have equipment to shave the tire. The shop manager showed me a service bulletin stating AWD Ford vehicles could have 3/32" variation. I wasn't comfortable with trusting a tire company service bulletin, so we referred to the local Ford dealership. The service department faxed over a page from their computer repair manual which said 98 AWD explorer could have 2/32" total variation on the open front carrier only. So we rotated the tires around and put the new one on front left. I figured worse case I would go back to the original shop and have them shave down the tire if didn't drive right.

Since then have driven about 3k miles with no noise, pulling, or vibration including the 1300 miles highway back home at 65-80 mph. Only consolation is have to be aware for future when rotating tires to only go left/right not front/back.

 

[SoNic67]

I can see how you can have a small variation on front, provided that the average between them is equal with the rear size. The open front will average the rotation speds. Also, probably that small of a variation between front and rear axles will not "lock" the center's vascous coupling (but it will spin the fluid inside slightly, generating some heat and drop in milage).
It is safer to start with all tires identical, because the need of roating the tires - in order to keep the wear equal between front and rear.

 

[TomCat_Ford]

This is why, in my opinion, it's important to have five matching wheels and tires so that you can do a five tire rotation. If one goes down, at least you'll have one other matching tire.

That is what I do with my Explorer (even though I don't have to...it's 4wd). I do a 5 tire rotation every 3,000 miles. Overkill? Maybe. But my tires have beautifully, even wear after 30K.

 

[RomeovilleIL]

Back to the original question at hand for Jeremy97, did you check the tires to see if this was the issue? If they are off a little it shouldn't be too difficult to move the tires around to get things arranged in a workable order. If they are all the same size, and aired to same pressure, then we have a different problem to potentially sort out.

 

[Lefty2053]

Quick question.. I took my Ex this morning to take the wife to work as we got a lot of snow. The road or course was plowed once but there was still uneven parts on the road where one side of the car was on pavement and the other on packed snow and powder. I felt s slipping or what felt like a rough piece of road a few times. Is this normal?

All tires are the same with even tread . I never felt this on my trip home with the car of 65 miles. Just this morning in the snow.

1997 AWD 5.0

 

[SoNic67]

When it's really cold outside it might take a few seconds for the limited slip in rear diff to kick in. You need that limited slip when one tire is on snow and the other on pavement.

 

[Lefty2053]

When it's really cold outside it might take a few seconds for the limited slip in rear diff to kick in. You need that limited slip when one tire is on snow and the other on pavement.

Thanks, I do believe it was the rear I was feeling.