New truck - 4x4 Clunk

[v8_dave]

Hello all,

Well, I bought the truck knowing the 4x4 was not used for a long time since the shift motor broke its little bushing a year or two back. But now that is fixed, when engaging 4x4 for the first times on a paved road, I get a firm clunk (not metallic) that travels right up from your feet from the floorboards. Have not tried 4x4 low as I have not been able to take it off pavement yet. Ideas to check out? The fluid in the transfer case is a dirty brown but full. The fluid in the front diff is perfectly clean and full. It appears to have new poly radius arm bushings. Is it bad to drive like this if I want to take it lightly off roading this weekend?

Also, after disengaging 4x4, the front left auto-hub clicks lightly but a bit loud, even after several tries re-engaging and backing up 10+ feet. Is it bad to continue to drive like this in 2 wheel drive? Can I try to tap it to free it up or take it off and clean it up?

Thanks for all suggestions, Dave

 

[MrShorty]

But now that is fixed, when engaging 4x4 for the first times on a paved road, I get a firm clunk (not metallic) that travels right up from your feet from the floorboards.

Under what conditions were you shifting? My '92 is real quiet shifting from 2H to 4H when stopped or when moving and the hubs are engaged. If you shift from 2H to 4H while moving and the hubs aren't engaged, you'll often get a good clunk. The t-case has some magnets in it that spin the front drivetrain up to speed before locking the front and rear together. Of course, it isn't perfect at matching speeds, so there is a clunk when it locks as the front and rear drivetrain are locked together.

According to the owner's manual, the transfer case can handle this up to a good speed. I personally was never very comfortable with it, so I chose to slow down when engaging the 4wd when the hubs weren't locked.

FWIW, since you haven't tried 4L, yet, I will add that mine almost always clunks when shifting into 4L. The gears in the transfer case aren't synchronized and there is often a clunk as the gears mesh.

I would also add that, because 4H locks the front and rear together, I wouldn't put it in 4H on a paved surface. Too much opportunity for things to break.

One of the common problems that seems to crop up with the auto hubs is that they don't always disengage reliably. You might pull off the hubs and see if they are clean (there shouldn't be a lot of grease in there). If they have a lot of grease in there, try cleaning them out real good and reinstalling them to see if that helps.

 

[v8_dave]

Thanks for the help! Well, the shifting is not the problem, it goes into 4H fine, its just when in 4H it clunks or POPS badly under load. I tried it on 4L too, same problem. I had it on the lift today and we think it seems like either the auto-hub is not staying engaged and popping in and out OR the transfer case is slipping the chain. How do I determine which is it? My thought was to just tape a line on the shafts and watch them while my buddy idles it in a tight circle to make it pop. Thanks again, let me know what you think of the situation now too.

 

[MrShorty]

I must have badly misunderstood what you were saying, sorry.

If you're engaging 4H or 4L on a paved surface and turning, you will get popping, it may be normal. Again, need to know more specifics of the conditions you are testing this under. In 4H and 4L, the front and rear are locked together. Any differences in front and rear tire size or while turning, and you put the drivetrain under stress. Under low traction conditions (mud snow sand etc.), the tires simply slip to relieve the stress. Under high traction conditions (pavement), the tires don't slip as readily, and you can get other noises or effects as the tension releases (including things breaking). If you're still testing on pavement, the noises may be "normal" but you need to get it off the pavement to see what's really going on.

Of course, the auto hubs are known for problems, too. If the auto hubs are "slipping" that could come up as a pop or clunk.

What exactly did it do when you had it on the lift? Did at least one front and one rear wheel spin? With open diffs, that would be normal.

When auto hubs go bad, they can make many different noises. I don't hear of a lot of issues with the transfer case chain. I won't say it's impossible for that chain to stretch and slip, but I would suspect the hubs before the chain.

 

[v8_dave]

That is perfectly OK, I appreciate the help always.

That is good news, last thing I want to do is replace the case. Well, I tried the truck on soft dirt and have the exact same symptoms of the clunking and popping. I will try to pick up some JY hubs tomorrow. Its a very stiff pop and clunk too, scary hard, something up front is slipping or breaking haha.

On the lift we had it in 2WD and spun the driveshaft and felt for play and listened for the auto-hubs and had guys hold the tires in place too to get an all around feeling for how it was working.

I will let ya know how the hubs go! Thanks again!

 

[v8_dave]

Picked up an auto hub from the JY today for $55, major difference in the teeth on the hub itself, mine were all word down and the grease in there was all thick and caked up. Now the truck drives perfectly in 4WD. Thank you for the reassurance, I have a great truck now for under $500 registered and insured.