4x4 hopping and lurching

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mca6501

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I have a 1988 k2500 that has major issues when 4wd is engaged. All four wheels have power but it will lurch to the left or right very hard at random almost constantly while im moving and the steering wheel gets tugged each direction causing the truck to swerve all over the place unless I really actively keep it going straight. Also sometimes the truck seems to hop as the wheels rotates at slower speeds from the drivers side. Everythings stock and the tires are all the same size, does anyone have any clue what could possibly be wrong?
 

IOWNJUNK

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Different gearing in front and rear axles is my guess.

Or maybe it has a locker?
 
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poncho62

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CV joints are beat.....maybe

This is when you are going straight, right?...not turning sharply?....4Hi or low or both?
 

1997chevydriver

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Different gear ratios. Someone probably swaped rear axle without checking gearing.
 

mca6501

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This is in 4hi just going straight, once the snow clears up a bit im going to check the ratios on both the front and rear to see if somehow someone replaced one before I got it.
 

great white

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Hmm, I would normally say some one hand grenaded the 10 bolt rear and swapping in a replacement but a 2500 should have either the semi floating 14 bolt or ff 14 bolt rear.

Less likely one of those would pop.

Still , 1988 was a long time ago.

Anything could have been done to it over the years from gear change to axle swap.

"Hopping" would indicate different front and rear final gearing though....

Rear gears are relativelyneasy to find out. Just jack the rear and rotate the tires once while counting driveshaft rotations.

The front is a pita. You have to get all four off the ground to check that. The driver front tire is always connected to the differential, the problem is it doesn't turn the shaft (or shouldn't) until the transfer case is engaged. Even if there is enough drag that the front shaft turns, you can't be sire or not if the rotation is accurate because of the side gear rotation....
 
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AirmanSkee

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But, on the drivers side of the front diff, you will see a 3-4" black plastic "breather" that will have a hose running off it. You can pop off that hose, and wrench of that cap, and depending on the company of gears, you might be able to see the stamping of the ratio. Thats how I found mine. You might have to drain the fluid to see the gears.

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mca6501

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Would lifting all four wheels while having the truck in 4hi and putting it in neutral engage the transfer case so i could rotate the wheel and check the ratio that way?
 

AirmanSkee

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Yes it would. Or unscrew your your actuator on the pass side of the front diff. Then inside the hole, push in with a socket or something straight to engage the front diff. Spin a tire and count the rotations of the shaft compared to one rotation of the front wheel.
 
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