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4x4 Actuation Note: S Trucks and Fullsize w/Autolocking setups

Discussion in 'Chevy Trucks' started by derekbroerse, Jan 9, 2005.

  1. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    There is a lot of talk about trucks with problems going in and out of 4wd. I'm sure a lot of them are the actuators as people are trying, but here is a freebie tip to check first:

    We had similar problems on my brother's '88 S15 Jimmy, slow activating and disengaging, and the transfer case seemed awfully noisy compared to what it should have been. We talked about it amongst ourselves and also with some people we know... and then looked into it.

    What we looked at were the tires of the truck. Yes, they were all P235-75R15's, but the fronts were a different brand then the rears. Now as we all know, a tire size is a NOMINAL SIZE, and while mathematically all 235's should be the same size, they are NOT. Some careful measuring revealed that the fronts were almost 1/4" taller than the rears (thru different brand manufacturer as well as amount of wear, 1/4" is NOT a lot of difference and the number can be a lot more!).

    Wondering if that little of an amount would do it, we borrowed a fully matched set of Goodyears from my truck and tried it on his. The results were instantaneous: The truck shifts in and out of 4wd immediately and the howling background noise caused by the transfer case is also gone.

    Yes, I realize that the S trucks use a vaccuum setup, and are not as troublesome as the electric setup on the fullsize, but it only takes a few minutes with a tapemeasure and a level to get an accurate measurement and it is a lot cheaper than replacing the actuator potentially needlessly. And we proved the problem by putting his old tires back on again... naturally the problem returned. He went off to Walmart to get a set of Goodyears (got a real deal on the set too).

    Like I said, with differences in manufacturing specs and one pair being worn more than the other, 1/4" isn't much, especially when you consider that an LT truck tire (A/T style) can easily start out with a tread depth of 1/2"--a totally bald one can be 1" shorter in height than a new one.

    Just a little free advice.