I am pretty new to the forum but have had a toyota for about 7 months. I recently put a motor in a truck i picked up for $500 w/out an engine or trans. When I put the truck into 4wd, it gets very jumpy and steering becomes very difficult. The truck seems to want to pull extremely hard to the left and it takes a good bit of muscle to get it to stay straight. I have no clue what the problem is. BTW, the truck is a "91 ext cab pickup w/ a 4 inch lift and 31's. Any help would be greatly appreciated.

 

What kind of surface are you driving it on when in 4wd?

 

It does it on the pavement which i kind of expected and then it also did it in the dirt just as bad and that is why i thought something was up. It has seen just a little offroad use since i got it. A few small trails and a couple of hillclimbs

 

Are you sure the gears in the front and back Diffs are the same? It sounds like they are not.

 

Ditto.

Get it figured out soon - do NOT engage 4WD until you KNOW that the gears are the same front & rear. If you do, and they're different, you'll tear up the diffs, transfer case, tranny... all sorts of stuff.

 

How do i check the gear ratio because i am pretty sure that at least the rear (hopefully front too) have been changed because this truck used to have 36" tires on it.

 

you also may want to know if their is a locker in the front/rear

jack the front end up... (xfer in nutral) lock the hubs(if you have man hubs) and spin the tires. if one goes backward or doesnt spin you have an open diff.

if the tire spins the same direction and speed, then jack up only 1 front tire and try it again. if it wont spin you have a locker/Limited slip in the front and that would explane why it crabs so bad.

as for determining ratio. (open diffs) jack one tire up, spin it one rev and count the number of turns the drive shaft makes. just over 4- 4.10 gears... 4.5-4.56 you get the point

 

With an open diff, you have to do TWO full revolutions of the tire to get the pinion / driveshaft to turn one full revolution. Might cause a little confusion to get a 2.25 gear ratio ( one open diff tire spin with 4.56 gears).

Mike in AR

 

Another suggestion if you feel like trying: You could disconnect the rear driveline, put it in 4wd, and see if it acts the same. If it still pulls, it is not a gear discrepancy.

 

If it's pulling badly, it almost sounds like one of the hubs or CV joints is broken.

 

I agree that it could be the CV's if it pulls. One CV could be busted and then you only have one wheel spinning up front which would cause lots of pulling.

 

Do you have manual hubs? If your cv's are good, try rebuilding them. It is not hard, and there is a tech write-up on how to.