acting weird since I switched tire sizes

cucmd1 · **Posted:** Sat Aug 22, 2009 7:15 pm

After 55,000 miles on a set of Goodyear Silent Armor's (235/70/16), I replaced them with the same tire in the 245/70/16 size. The auto transmission jerks/shifts hard/feels like it slips a little, ESP is messed up, and all around it drives like crap since I switched tires. There is a vibration and steering wheel shake at 65-70mph, and again at about 35-30 slowing down. Do you guys think the problem is: alignment, tire balance, or something else? My brother in law is telling me it's my U joints, and I'm thinking the tires might need re-balancing, but that's not going to help the transmission shifting funny. Do KJ's have a programmer that resets the shift points like the JK's do? (hypertech/superchips/procal)

I've also searched and can't find why it's kicking gas back at me every time I fill up. Is it just a vent hose or something? I'm at 77000 miles now. It was probably the best vehicle we've owned until I switched tires. Thanks for the input.

Clay

nightdrv · **Posted:** Sat Aug 22, 2009 9:12 pm

Not to thread jack, but I get the same gas up-chuck sometimes. Twice now. Only at 15k miles. No idea?

As for your weird characteristics, I think it's coincedental. Shuddering at different speeds is more like lbj's or wheel balancing. Trans shudder could be anything. First check would be the trans mounts.

Just my .02

bugnout · **Posted:** Sat Aug 22, 2009 9:17 pm

I would suspect tire balance or alignment.

For the tranny shift issue, you could try disconnecting the battery and leaving it off overnight. That will but the ECM and TCM into learn mode again.

Boiler · **Posted:** Sat Aug 22, 2009 9:23 pm

Gas upchuck is very common. When I bought mine in January it did it the first 3 times. I checked on here and KJ Country and saw that it happened alot and I didn't see any fixes besides slowing down the fill rate when it's close to being full, and never try to squeeze more in. I have the 20-1/2 gallon tank, and I let it get to where the light comes on or later. Then when filling I fill rapidly to 16 gallons, then put it fill the rest by hand at a slow rate and when it pops I stop. No spill.

KJKev · **Posted:** Sat Aug 22, 2009 9:41 pm

Have the tires rebalanced. Steering wheel shake has pinpointed it for you.
To verify, swap the front and rear tires. If is then shakes in the seat, you know its the tires.
The computer might not yet be compensating for the different size of tire and that could be causing your tranny situation.
you could disconnect the battery but you don't have any codes. But if you do, you only have to leave it off for a few minutes. Then see if anything is different.
KJKev

tomsjeep · **Posted:** Sat Aug 22, 2009 10:36 pm

On the gas thing, I find that turning the nozzle so that it's almost upside down it seems to work better... I don't know if that's got anything to do with fluid dynamics, or just luck.

I upsized to the same tire as the OP. I haven't noticed any transmission issues or changes in shifting. It's not that big a difference in tire size.

cucmd1 · **Posted:** Sun Aug 23, 2009 10:31 am

thanks. I'll try disconnecting the battery today. 5 minutes? 15 or more? As for the gas, once it started that I slowed down. the issue is when my wife has to fill up. she'll either make a mess or refuse to put more than the absolute minimum in. I'd love to get that fixed so I can quit filling it up for her! I'll see about the tires getting rebalanced too. I thought that was a small enough tire size change not to cause problems. Mileage has also been awful since I switched. Maybe it's time for some new spark plugs while I'm at it.

nightdrv · **Posted:** Sun Aug 23, 2009 1:59 pm

Gas wise: I'm talking about the automatic settings on the pump nozzle. You know, there's 2 click points available? Well, twice now at different pumps in different states.. it just doesn't stop.

JMSMN · **Posted:** Mon Aug 24, 2009 12:25 am

I just put 245/75R16 treadwright mt tires on sat morning. Everything feels fine but my esp has been messed up. When I am driving and the trans has to shift out of OD, right when it downshifts my esp comes on. And then when it shfts back into OD the light goes off immediately. Any thoughts?

cmohr · **Posted:** Mon Aug 24, 2009 2:41 am

See "Pinion reset"

When you change tyre size the info the ecu gets from all the different sensors is incorrect according to the ecu table, thus, It tries in vane to compensate for the errors. Your auto transmission will hunt up and down looking for the correct gear, fuel and timing tables will play up giving you damaticly less fuel ecomonony and less power. Abs and esp will also be affected as the readings coming from wheel sensors fron and rear left to right will not correspond with the table the ecu has for a particular gear and speed.

The petrol V6 is more prone to issues than the CRD's, so if you are getting these symptoms, chances are a "Pinion reset" will help. You local dealership should be able to do the job. Remember they need to set the new tyre size in both the ecu and the abs module for it to work. Early models use a "Revs per mile setting" later modles you can actually choose a tyre size.

acting weird since I switched tire sizes

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