4x4 clunk Question

[jwaring]

Hey guys, I'm new to the forum but love the site!

I've got an 06 4x4 and twice I've experienced a sharp clunk when decelerating with the 4x4 engaged. When I say sharp, I mean it jolts the whole truck. It's not violent but not subtle either- Both times I’ve been going down a hill slowly (on a slippery surface) with the Tow/Haul mode on to slow the truck. Is a clunk in that circumstance normal? It usually happens when the truck is almost at a stop (maybe 5-8 mph) The truck only has about 8,000 miles on it so it seems odd for it be a wear or spline issue. Not sure if the tranny is shifting abruptly (down into first) to make the clunk or if it’s related to the transfer case…? I know the output shaft on the trans will clunk some but again the truck is fairly new and this has only happened in 4WD. Any thoughts? Thanks everyone!!

 

[Elk]

4HI or 4LO? In 4LO and Tow/Haul engaged, mine does pretty much what you describe.

 

[jwaring]

Now that you mention it, the first time I felt it, I was in 4Lo. This latest time I was in 4Hi.

 

[Kleetus]

You're probably feeling the slack in the chain in the transfer case, mine kinda does it too... not saying it's right, but that's kinda how they behave.

 

[Yellowsub1962]

if the RPMs jump and remain higher than they started as it bangs, then it's downshifting... otherwise it could be driveline wrap up and is a normal occurance in 4 wheel drive. the othe posibility is just all the "slack" like said above, but is likely a combination of all the slack, R&Ps, T-case gears/chain, Trans gears, and maybe a little fluid slap in the T/c for good measure.

Does it happen oonly coming to a stop? or during a steady decent with your foot off the brake?

Try manually putting it in 1st gear and going down the exact same hill. If it doesn't do it, it was prolly a downshift, or the "slack" being taken up from the momentary lack of connection during the downshift. You can also "blip the throttle" a tiny bit and see if it does it. That will temporarily slack the driveline and it goes from holding back to pushing to holding back again.

I'm sure you know, but in tow haul mode, the truck will automatically downshift with brake pressure.

HTH,
PSD

 

[Kleetus]

except when it's in low range... tow haul doesn't work there...