klunk when in 4A and applying pressure quick

[RedExpy]

ok.. been getting klunk lately when I am in 4A (haven't noticed in full 4x4) but it happens when...say you are on an incline and have to add power to get up hill ( noticed in reverse backing up snowy drive)... almost as if the computer noticed slippage and engaged 4x4 so the question i have is...

in 4A--- is the transfer case fully engaged or is that where the computer decides to engage the system? Is the system engaged at the front differential???

Truck had new front differential installed ( i have service records) but i cant really tell where the klunk comes from other than installing a gopro or something and listening to recording...

ideas????

 

[daye190]

hey that just happened to me you have to ad an additive to your transfer case sold by ford motorcraft additive,friction,modifier this also happened to my 03,expedition and just recently happened to my 08,expedition its a small bottle that smells like hell but it does the job ..buy the bottle and have any lube center put it inside your transfer case .hope this helps

 

[Snag]

My 05 was doing the same thing after I changed all the fluids. I used full synthetic in the rear, it was labeled as ok to use in limited slip applications. Guess for a Ford it wasn't, so added the friction modifier and clunk went away.

 

[GalaxyPilot]

I get this too but haven't changed any fluids in the drive line. Getting close to 100k, so will probably change them soon. I always assumed it was just the transfer case putting it in and out of 4wd, but you think it's just fluid worn out at this point?

 

[powerboatr]

4A is all engaged except one clutch in the transfer case. I bet the computer thought it was slipping and went full. its a torque demand system , real close to all wheel drive but not by much.
my 4A is noisy sometimes..but if i shift to 4h for a few feet it goes away once 4A is re-selected. My 2013 F150 did the same thing. so i think its a behavior of the system.
we run in 4A pretty much most of the time, we have roads that get slick as owl snot on a whim