4x4 pops in and out

[Dan Vinke]

Well, my ST has done this since the day I bought it 2 years ago, but now that I have it lifted with some better tires, I really wanna go 4-wheelin.



I've always worked on my own vehicles (put a new motor in the ST last summer myself), but this is the first 4x4 vehicle I have ever owned or worked on, so I don't quite know all the in's and out's of a 4x4 system.



Here's what it does:



In 4 high or 4 low, when given anything more that very light throttle there is a loud "clunk" and it's no longer in 4x4. If there's very little load on the system it will stay in 4 and won't clunk, but the second I give a little bit more gas it clunks and pops out of 4. Sometimes, however, it will clunk a little bit lighter and still stay in 4 and clunk lightly here and there.



Sometimes after it clunks and pops out of 4, if I don't let off the gas right away I can here a rattling type sound - it sounds very similar to when somebody puts a car in park before it has completely stopped.



Here's the weird part though - I can put it in 4 high or 4 low and go ANYWHERE I want to in reverse with it staying in 4x4 and not clunking one bit. I can give it as much gas as I want to, spin all 4 tires, and put a large amount of load when going in reverse.



I tend to think it's one of the auto locking hubs popping in and out. But the rattling noise seems like it might be the transfer case.



I dunno - like I said I don't know a whole lot about a 4x4 system.



Any help would be appreciated.

 

[scott degroot]

Do any of the indicator lights for the 4x4 system ever start flashing? Sounds like it could possibly be a problem with the shift motor on the transfer case not holding.

 

[Todd Cloutier]

You aren't trying this on dry pavement, are you?



The ST doesn't have auto locking hubs. The front portion of the drivetrain is always spinning with the only disconnect being in the transfer case.

 

[Todd Z]

LOL.... I do stupid things with my st in 4wd on dry pavement...LOL



Sounds like the shift fork in the case is shot or out of adjustment....



I think since it holds in reverse due to the torque applied is in the other rotating direction...



See if it can be adjusted, IF not sounds like a new motor or an internal check is needed..



Todd Z

 

[Dan Vinke]

No lights flashing, and I know not to drive on pavement in 4.



I thought it had auto locking hubs, but if the front diff is basically like a spooled axle then it must be something with the transfer case.



How can I tell if its the shift motor? Is there a way I can tell if I pull it off?

 

[scott degroot]

The shift motor not only shifts the transfer case but it also holds the shift so it does not pop out of gear. I don't know of any way to really check the shift motor out of the vehicle, you could monitor the shift motor position with an NGS but I will assume that you don't have one. Other than checking the electricial signals to the motor about the only thing you can do is to replace the shift motor. Chances are that it is the motor failing on you but being that I said that it will end up being something internal. FWIW the 2 biggest reasons for failure are the actual switch itself and the shift motor.

 

[Ken Hibbs]

Today in the snow it would go in and out of 4wd, sounds similar to hitting expansion joints on the highway. When on the exit ramp going uphill, popped out rear started spinning, let off the gas and went back in. Probably shift motor from what I read above?

106,600 miles

 

[Vic Sorlie]

Have you kept up with transfer case fluid servicing? What's condition and level of fluid in there now?