Ok, since I'm new to the 4x4 world, I am confused. If I get a flat and use my spare front or back, is it OK to switch to 4 wheel drive if needed or best to leave it in 2 wheel drive until I get a new tire? The reason I am asking is in May I will be driving (military move) from N. Carolina to Alaska and in case I get a flat, I would like to know what's the best thing to do w/o damaging something.

 

You'll be fine in part time 4wd as long as you are not on dry pavement - regardless of if you have the spare on or not. If you have a locker or limited slip, then it would be much better to have matching tires on that axle.

 

I haven't closely read what's on the sidewall of the spare but alot of temporary use spare tires have a speed and mileage usage limit that is there to help prevent damage to the driveline. Personally I think it's stupid to have one but if I recall a truck equipped with dual exhaust doesn't have the room to fit a full size 20 inch spare. The dealership should replace/clean all the parts affected by this. I mean Chrysler will pay them to do it, it's not like anything comes out of the dealers pocket. If you're being treated like this you should go above the service manager's head and talk to the dealer principle.

 

Oh ok, so if I had to use the spare on the rear of my truck (3.92 LSD), should I switch a frt tire to the rear and the spare to the front? Would that hurt the frt diff/transfer case?

 

You should get rid of the crap spare and if one will fit get a rim and tire at least the same height as yours, the width really doesnt matter. Or take the spare off and then when you call the Chrysler Service they will tow you to your house or the dealer, whatever then you just get a new tire for your rim and put it on. That is if you were not going anywhere, also be sure they tow on a flatbed or you have to put the truck in neutral and the transfercase in neutral also. Still not a good idea to tow a 4x4. They used to take the drive shafts off. Too lazy now I guess.
I think the fact they supply that rim and tire as the spare and may or may not be the same size should be the problem here and not your problem they should be making it look like new under your hood also. It's warranty what do they care they get paid.

 

 

If you are planning on driving it for hundreds of miles it would be a good idea to swap the "real" tires to the back.

Best advice in this thread is to buy a real tire to go on the spare (assuming it will fit in the spare well). On my SLT the 17's came with a 5th matching tire, seems odd that the 20's come with a different tire.

 

I agree with 72combo, and have griped in forum about the STOOPID choice to provide a Limited-Use / Off-Size / Bald-Shouldered Spare Tire on a Factory 4x4 Truck. Get rid of it, trade it for full-size full-use spare.

The spare is a different diameter, especially under real-world driving conditions. That means any prolonged driving in 4-wheel (hi or low) will produce a significant amount of binding. If any amount of that was on "dry" pavement - less than enough snow / sand / gravel to allow tire to slip 1in for EVERY rotation (that's 50ft for every mile driven) - then the best you can hope for is uncomfortable wheel-hop and the worst is something broken in the differential or axle.

I know. I learned this lesson several years ago. I drove an OEM Spare (off-sized by 1.5in) down off a mountain and into town in a Dakota where the front diff had somehow locked in 4-wheel. The result was a broken / sheared propeller shaft. Ouch!!

So, everyone with 4x4 needs to remember to deal with that lousy Limited-Use Spare.

 

According to my calculations the 275/60/20 stock dimeter is 32.99"

The 235/85/17 diameter temp spare is 32.73"

I wouldnt sweat a .25" diameter difference even with an LSD for short periods, which is exactly what the temp spare is designed for. Its made to get you to a place to fix the bad tire, not take you cross country in a blizzard.

There is plenty of room to mount a full size spare with the dual exhaust on mine if needed it appears.

IMO driving at highway speeds with any part time 4wd truck in 4wd lock for long distances is going to overheat parts unless the highway is mud or gravel.