Can I replace only 2 Tires on 1999 4wd Exporer?

Had an alignment problem which cupped the two front tires. I moved front cupped tires to the rear and now have a bad shake in rear of car when driving over 60mph. Tires were balanced but because of cupping they cannot be balanced properly. I would like to replace the two rear cupped tires only. Depending on who I talk, I have been told that I need to replace all 4 tires - or - I can replace just two as long as the two new ones are on the same axle. Who is right?? I have a 1999 4wd V6SOHC with tow package (posi rear). I do not have fulltime 4wd although I do have automatic 4wd. Thanks!

Had an alignment problem which cupped the two front tires. I moved front cupped tires to the rear and now have a bad shake in rear of car when driving over 60mph. Tires were balanced but because of cupping they cannot be balanced properly. I would like to replace the two rear cupped tires only. Depending on who I talk, I have been told that I need to replace all 4 tires - or - I can replace just two as long as the two new ones are on the same axle. Who is right?? I have a 1999 4wd V6SOHC with tow package (posi rear). I do not have fulltime 4wd although I do have automatic 4wd. Thanks!

common sense.who told you something like that?
sounds like someone whant some money :devil:

A matched set is best.
Different degrees of wear, combined with
varrying air pressures can lead to
problems with the 4x4.

Umm... sounds fimilar - two different answers. So because of the auto 4wd the tire diameters on all 4 tires need to be the same with each other or it will cause the 4wd to think their is slippage on the road surface causing the auto 4wd to continually engage, wearing out the drivetrain...?

A matched set is best.
Different degrees of wear, combined with
varrying air pressures can lead to
problems with the 4x4.
:nono:go to school man.im certified.as long as the two tires your not replacing have no physical damage they will be fine.if they are worn common sence says replace.if the sides are gone comon sence says replace.if they have eggs comon sence says replace.if the tires are fine and you are using the same size tires it will be ok.trust me.

air pressure is important,i give you that.

saperich is correct- A4WD has to have tire circumference within 1/4 inch to work correctly

saperich is correct- A4WD has to have tire circumference within 1/4 inch to work correctly
.if the tires are fine and you are using the same size tires it will be ok.trust me.

Thanks everyone. I decided to replace all 4 tires. Wa fortunate as Americas Tire Co. (hope its ok to mention retailers?) gave me $115 credit for my old tires which made the purchase very worth while.