Weird clunk after switching from 4wd to 2wd

[turbotaguy]

My 04 Ranger 4x4 (auto) has a weird clunk. While driving I get a clunk about 5 seconds after I switch from 4wd high back to 2wd.

I often use 4wd high in my neighborhood, then switch back to 2wd once I get to the main road. This clunk is like clock work......driving in 4wd high, switch to 2wd and count to 5....CLUNK. It almost sounds like I am hitting a big bump in the road.

I have no problems or noises driving in 2wd all day, or in 4wd high all day. Just when I switch from 4wd high to 2wd.

Any ideas?

 

[bigcountry]

do you switch it on the go and on pavement??? if so thats why you hear a clunk if your driving on ice or snow on the street then 4x4 is ok but you need to be either in neutral or stoped to engage it. your 4x4 system is not designed to be used on pavement when you already have good traction you can tear up alot on pavement in 4x4 like tires for one and the xcase and front axle. so what you need to do is find a field or lot and use the routine you use everyday in your neighborhood in the field or lot and listen to see if you get the clunk if so try to stop or put the truck in neutral and engage 4hi and then move slowly for a few feet then have at it the system needs time to engage. now if what you are saying is every time you swtich from 4x4 to 2wd and you can count to 5 and you hear a clunk that means its not doing anything bad its just doing what it is designed to do which after to much of what you are doing it will tear up the 4x4 engaing mechanism

 

[4x4mike2004]

assuming you are engaging it the correct way, it could be a u-joint. also check your fluid levels.

 

[bigcountry]

thank you 4x4 mike i forgot that little tid bit. and to check the ujoints grad the front drive shaft and if it turns either way than ujoints are bad and do the same for the rear driveshaft.
make sure you check the front ujoints with 4x4 engaged and with out it engaged and please not to insult you but make sure the truck is on flat ground with the ebrake on and truck off

 

[Jspafford]

do you switch it on the go and on pavement??? if so thats why you hear a clunk if your driving on ice or snow on the street then 4x4 is ok but you need to be either in neutral or stoped to engage it. your 4x4 system is not designed to be used on pavement when you already have good traction you can tear up alot on pavement in 4x4 like tires for one and the xcase and front axle. so what you need to do is find a field or lot and use the routine you use everyday in your neighborhood in the field or lot and listen to see if you get the clunk if so try to stop or put the truck in neutral and engage 4hi and then move slowly for a few feet then have at it the system needs time to engage. now if what you are saying is every time you swtich from 4x4 to 2wd and you can count to 5 and you hear a clunk that means its not doing anything bad its just doing what it is designed to do which after to much of what you are doing it will tear up the 4x4 engaing mechanism

What?!

The system in his truck is a live front axle. You can shift into and out of 4HI at any speed. Make sure your not spinning your tires when you shift into 4HI though.

There should not be a clunk. I had a 2001 Ranger and my wife 2002 Sport Trac... Both use the same exact drivetrain as your truck, they do not make any noises when shifting out of 4WD.

Sounds like something is hanging up and letting go with a thud. My 89 B2 does this when I shift back into 2WD with the manual case, but I attribute it to being old and as long as it works, I'm not messing with it.

It could be the u-joint as mentioned above. You only have one in your front driveline and that is where the driveshaft meets the differential.

 

[bigcountry]

i said that because if it is a constant 5seconds everytime then it sounds like something he is doing is wrong hence why i said to go out to a field and try it and also why i said to stop the truck or put it in neutral when going into 4x4 i dont know much about the live axle on the new ford trucks but i do have some exp. with different 4x4 systems and they all work in about the same way. im not tryin to insult you or say your wrong im just tryin to figure out why its 5seconds all the time when it goes from 4x4 to 2wd. yes it does sound like something is hanging and then releasing but my thing is why is it constant not like it happens like 20 sec here and the next day it is 30 or a week later its 5seconds thats where its not making sense and he will never know if he doesnt go out and see what will either change the clunk time from 5sec or to stop it all togther

 

[AllanD]

Like I just said in another topic just because you switch OUT of 4x4 doesn't
mean that the internal parts of the t-case do...

When you switch out of 4x4 if there is relative tension between
the two driveshafts the tension must be released before the
internal shift fork and collar parts can actually move.

AD

 

[turbotaguy]

Thanks for all the input guys. It really sounds like some type of tension that is being relieved as AllanD said. I'm going to experiment with switching back to 2wd before I reach the main road while I'm still in the slushy stuff and I'm going to monitor things a bit more closely.

Also, tomorrow when I get a minute I'll check out the front Ujoint and the tcase fluid level. I just bought the truck (it has about 54k miles on it) so the fluid level may be low. That might be worsening the "tension release" and making a sound when it probably shouldn't.

 

[turbotaguy]

Just an update to close the loop - I finally had a chance to do a fluid change and wow, was that stuff watery. It really looked like dirty brown water. I drained it and filled up with new fluid and the clunks are gone.

Nice to fix something for $6.50 in new fluid and 30 minutes of work!