Engine/Transmission (1998.5 - 2002) unknown clunk

[cmills]

my truck is a 99 4x4 with the 5 speed. It has a clunk that I can't figure out it only happens when I am pulling the trailer and the more weight the worse it is. I am almost 100% sure that the trasmission or transfer case is hitting the floorboard but I can't figure out why, the u-joints are good as are the motor mounts and the transmission mount is new. It only does it when I am up to speed going down the road. The truck has 240,000 miles on it, the transmission only has about 30,000 on it but the transfer case is the original. I have noticed that there is some oil leaking between the transfer case and the transmission and it looks kind of gray like it might have some wear metal in it. Could it be something internal? but if it is wouldn't it do it unloaded also?



Sorry this is so long but I am out of ideas and need help



thanks,

Cory

 

[Cummins724]

my truck is a 99 4x4 with the 5 speed. It has a clunk that I can't figure out it only happens when I am pulling the trailer and the more weight the worse it is. I am almost 100% sure that the trasmission or transfer case is hitting the floorboard but I can't figure out why, the u-joints are good as are the motor mounts and the transmission mount is new. It only does it when I am up to speed going down the road. The truck has 240,000 miles on it, the transmission only has about 30,000 on it but the transfer case is the original. I have noticed that there is some oil leaking between the transfer case and the transmission and it looks kind of gray like it might have some wear metal in it. Could it be something internal? but if it is wouldn't it do it unloaded also?



Sorry this is so long but I am out of ideas and need help



thanks,

Cory

I had a clunk like that a few years ago & it too only happened when towing... . turned out to be the lower track bars that hook to the axle & right below floor boards. Changed them out for a set of Skyjacker bars & problem cured. Your bars are probably loose or bent... . very common problem.

 

[MarkMiller]

Begin by grabbing all four front links and twisting/jerking them around. You most likely will find one is loose or a bolt is worn out. It only takes a little bit of slop to make a clunk. Also check the adjuser cams and look closely to see if they are shifting. I have to add a washer under one of the nuts on the passenger lower link. For some reason the nut was hitting threads before getting enough torque to keep it tight. I now run adjustable links from skyjacker. Still have to be careful to keep them tight.



The next thing to check os the trac bar. They are notorious for going out on 2nd gens. I have a Thuren. One of the best products I have ever bought.

 

[cmills]

clunk

Thanks guys, but I already checked those and they are fine, any other ideas?



thanks,

Cory

 

[SAndreasen]

does the noise come and go like when you hit the throttle rapidly and let off?

 

[DWest]

at low speed sharp turn

When I back out of my garage mine klunks when I turn sharp to exit the drive and it's right under the floor on the drivers side. Any ideas? DW

 

[Cummins724]

When I back out of my garage mine klunks when I turn sharp to exit the drive and it's right under the floor on the drivers side. Any ideas? DW

I would double check the trailing bars..... they are most common for these symptoms. I checked mine briefly & blew them off saying "they are good" & later found out that I was wrong because you can't put a load on them to make them clunk in the garage. I found that the best way to check them is to stop in the middle of a hill & let the truck drift back..... hit the brake hard & get a friend to listen from outside.

 

[Allnew2Me]

It may sound silly but check your hitch and make sure all the bolts are tight. Also, check the reciever to see if the pin hole is elongated and may be allowing the drawbar to clunk.

 

[cmills]

clunk

I found the problem, its the transfer case, it is trying to kick out of 2 hi and go into neutral, if I put it in 4 hi it does just fine. I'm going to unhook the front driveshaft and run it in 4 hi when pulling until I get it fixed. One question though do I need to unhook the vacume lines that go to the front axle so it does't engage or can I just leave them hooked up and let it engage.