'94 Blazer K-5

A friend just picked up a 94 Blazer (5.7 engine) and is having the following problem:
Wheels lock when put in reverse (and sometimes, even in forward gear).
Car has L2 285/75 R 16 tires on it but it's supposed to have 245's or 265's. He's wondering if the wrong tire size could be the problem he's having.
He does have a Tech II scantool but it couldn't get any data from the module. Data flashed on the screen for a second - but that's it. He says the scantool is working on other modules so I'm wondering if he could just have a bad module that is a) not sending data to his scantool and b) sending the wrong data to the tranny?
Any suggestions or help would be greatly appreciated.
Nadyne Nelson snipped-for-privacy@verizon.net
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I'm certain the K5 line of Blazers was axed in 1991, Unless someone knows otherwise. I would check really closely as to what truck we're talking about here. But whichever it is, I do not see the tire size having any effect on the current problem. As for the electronics, someone else will have to fill in those blanks.

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They did. They *ucked it up in '91 and then it got worse....
~KJ/TLGM

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