I'm thinking either my front hubs are locked or transfer case is engaged in 4WD, even though the push-button is showing 2HI. How can I check this?

Should my front driveshaft be locked if I try to turn it by hand? I've heard this should spin freely when not in 4WD, but I'm not certain.

I put the transfer case into neutral, made a light clunk, but putting it back into 2HI made a very heavy clunk. Is this normal?

I replaced my 4WD selector a few years ago, after the lights would go out, and the "service 4WD" light would come on. Haven't seen that happen since then.

Thanks

 

Try to make some tight parking lot style turns, if the front tires bind up, you may be stuck in 4wd. The front hubs don't actually lock on our trucks, but the r/s axle engages to the front diff instead.

I can't remember the deal with the front driveshaft...IIRC, it will still spin when in 2wd but I can't remember for sure. I'm going to move this thread to the GM Drivetrain and Suspension section and hopefully you'll get some more hits

 

#1) Your front prop shaft will not spin freely by hand, even if the t-case is in 2WD. That is normal operation of the Auto-Trac transfer case. The front shaft will be spinning while you are driving in 2WD as well.

#2) This also sounds normal to me. If you shift your electronic t-case into neutral for any reason, there is one best way to get it back out of neutral. Set the park brake, turn off the engine, turn the key to "on". Put the transmission into neutral(without the engine running) and then shift the t-case back out of neutral. It will clunk, this is normal.

If the engine is running, and the t-case is in neutral, the clunk will be louder and harsher when it shifts out of neutral.

 

I appreciate the responses. Good to know that neutral thunk is normal. Still it feels like the "auto" on the autotrac is engaged when showing 2Hi. The steering is heavier, vibration under foot, lower gas mileage. Is there any way to find that out?

Thanks

 

You could put it up on jackstands with all 4 wheels off the ground and run it in drive and see what happens. Word of caution...if your doors lock automatically, make sure that you leave a window open...ask me how I know

But honestly, if it were stuck in 4wd, it would bind horribly while turning at slow speeds on dry pavement.

 

When we were testing our job of installing a front end in my brothers d-max, he just put it in 4wd, did about 15mph in reverse and slammed it into drive and I watched the front tire, haha. I wouldnt recommend it tho. Like bud said, you should really feel it fighting in binding turning tight on pavement.

 

The linear encoder on the front diff is probably stuck. If you haven't checked the diff for proper oil level, I recommend doing so. They will go low and then the encoder seizes. Your T-case never disengages the front prop- your encoder is what "shifts" from 2WD to live front axle

Usually a stuck encoder throws a Service 4WD light but if the encoder or wiring is messed up it won't.

 

I think the problem has cleared after putting the t-case into neutral and back to 2HI a few times.

But, should it come back, is the encoder replaceable as one piece, or is that a rebuild on the front diff?

Thanks

 

I would need to check a parts explosion but I think there are a few clips inside the diff case that have to come off.

 

On the newer autotracs, the shaft will spin freely in 2wd. If it was me, I'd find some gravel, put in 2 hi. and stand on it.