mtalmage10887

I'd like to start by saying I am new here so forgive any broken rules. I recently bought a 1998 4Runner Limited 3.4L v6 and when I test drove the vehicle everything checked out fine including 4Hi and 4Lo. Didn't get to try out the rear differential lock. So the other day I randomly decided to check out the 4wd again as it was beginning to snow. It was for the most part dry pavement still which I know I'm not supposed to do but I didn't see any harm for a minute or two. So I stopped the truck, put it in neutral, pushed in the 4Hi button, it went right into gear and I began to accelerate in a straight line. But this time the entire vehicle was extremely jumpy like it would accelerate forward and then hesitate and then accelerate and then hesitate again. It seemed to switch between the two every 2-3 seconds. Its hard to explain but if I don't get any ideas ill make a video, post it to youtube and post a link. Please let me know if you have any idea what this could be. Thank you!

scuba

Sounds like the front differential could have a bad ring and pinion gear or the ratio is mismatched. First thing to do is check the oil in the front diff. If there are any large chunks of metal/ gear teeth then it's time to pull the diff and inspect further.

mtalmage10887

Yea I wasn't sure if the problem would lie in the front diff, front shaft, or the transfer case itself. I did notice a slight leak in the front diff when working on other things today. Thanks for the advice.

mtalmage10887

So I checked the fluid in the front diff and didn't notice any chunks or shavings of metal in it. One thing I failed to mention is when in 4hi and accelerating it pulls slightly to the right and is difficult to steer both right and left. Also when I let off the gas there is a lot of resistance when coasting. It is extreme enough to completely slow me to a stop and hold the vehicle in place at idle. Any other thoughts would be nice. I'm not confident enough in my ability to remove the front diff or transfer case, inspect, repair, and replace so would need to take it to a shop. Thanks for any other advice you guys might have.

Jomoka

First off, 4WD is not for use on pavement. Unless the surface is slippery in some manner, the drivetrain will build up tension between the front and rear wheels, unless you're going in a very straight line.

It's normal to feel a bit of resistance to the steering when you're in 4WD mode.

Are the tires the same size front to rear?

The pull to the side makes it seem as though you could have a worn bushing - allowing the wheel to get pushed out of alignment when it's under some torque.

Is the engine running smoothly when all this hesitating and slowing is happening?

As a wild card, I'm almost thinking someone may have swapped the front diff and put in the wrong ratio? The locking rear axle is probably a 4.30, non-locking V6 4Runners are usually 4.10, if someone swapped either end (adding a locking rear where there wasn't one, or replacing the front diff for some reason) they may have ended up with a mismatch. Normally, you're not supposed to use 4WD on pavement, but driving it in a straight line shouldn't produce any serious drivetrain binding.

aowRS

I'd vote for mismatched front to rear ratios.

The front diff is heavy and very cumbersome. Not easy to remove and a pain in the ass to reinstall. I've been there...



Andreas