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i have just replaced 2 wheels (that where crapy remoulds). some one hads told me that the 2 new tires and the 2 old ones are putting to much load on the transfer case and that they where not built to work that hard. i was wondering if this is true.

Depends on what gearbox you have

If it is a part time 4WD, as long as you drive on the road in 2WD, and only use 4WD on slippery surfaces, you will be fine.

All other gear boxes like Autos and 5 sp manuals with the AWD viscous centre diff, you will cause premeture wear

i have an impreza gx with full time all wheel drive

Well you don't have a transfer case so to speak, but you do have a viscus LSD between the front and back. This will wear out quicker than normal if your tyre diameters are mis-matched.
If you can't afford to change out your tyres for a matching set then your best best is to match both left tyres up and match both right tyres up.
This way the mis-match will be left to right.
You have an open-diff on the front, and an open diff on the rear so this won't be as much of an issue.
The car might not drive totally straight tho!

depends how big the tyres were, if they were all 195/65 15" should be okayish and depends how long it would have driven. Its possible a chance that transfer case would be 'wearing out' the only way to know if it has worn out is you would have no driving gear, ie. able to "drive" without the car moving and feels like the clutch has worn out/slipping then thats the transfer case worn out. Other thing if you're able to drive then next minute there is nothing just feels like slipping clutch but its not -

Hint - if your revs and speedo works then its gearbox problem. if speedo does not work while in gear with revs going up and down then its the clutch.

Cheers
AP

Just to be clear, when we say "transfer case" we mean the same thing as the Centre Diff in the AWD gearbox?
I'm wondering, if the LSD in the centre diff part of an AWD gearbox wears out, would that actually cause the car to stop driving? (like a worn out clutch). Surely it would just keep driving but act more like an open centre diff.....just like the EA82turbo "AWD" gearboxes which have an open centre diff?

AndrewT wrote:Surely it would just keep driving but act more like an open centre diff.....just like the EA82turbo "AWD" gearboxes which have an open centre diff?

Correct

The LSD part of the diff is simply a viscous friction between the front and rear outputs of the diff (or left and right outputs on a LSD rear diff) If it wears out, it then becomes an open diff.

As AP said, if the tyres are all the same size, just at different states of wear, the difference is gonna be minimal.

Yes AP also talked about how if the "transfer case" was worn then the car would loose drive similar to having a worn clutch, this is what confused me.