4x4 clunk

[rednecksrule421]

Hi there guys i was wondering if you could help me out with my 4x4 prob. Ive got a 97 4.0x control trac, the problem is when the awd engages or is in 4 hi and you give it any kind of throttle to put a load on it i get a terrible clunk. it sounds like it is coming from the front diff. i replaced a cv joint and that wasnt the prob.If you dont give it much throttle it doesnt clunk and it didnt do it when i took the foront driveshaft out. any ideas as to whether it would be the front diff or the transfer case. Thanks for your time guys.

 

[rednecksrule421]

anyone plz?

 

[PeterJ]

I just bought a 2000 with 104k miles on it on Thursday, and it clunks if taking off on ice while in auto. If I have it in 4x4 high it never clunks. I think the clunk is normal while it engages the auto.

I don't know the first thing about how this truck works but I have had a few 4x4s in my time. It has been my experience that the driver should ALWAYS make sure the 4x4 is completely engaged before trying to put any power down. Spinning rear driveshafts do not lock up easily to stationary front driveshafts.

That being said, have you checked all parts for grease and clean fluids?

After the first clunk while in 4x4, does it drive the front wheels?

Does it clunk more than once?

 

[rednecksrule421]

it is a consistent clunking and popping noise whenever you are under acceleration unless you really ease on the throttle as soon as the front tires start to spin. it doesnt matter whether its in auto or 4 high.

 

[maxcr3]

I had what appears to be the same type clunk on my 99 explorer. I tried axles, drive shafts, gears. I have a pile of good used parts in the garage! I finally changed the fluid in the transfer case (Amsoil oil). The noise immediately lessened and gradually went away. It never went away 100% but I can live with it knowing the source. It is not like I am going to drop a drive shaft or axle. At least I know what the problem is.

Evidently there are clutches in the transfer case. Changing oil or switching to Amsoil helped. I have about 15,000 miles on since I did the oil change. This spring I plan on changing the fluid again.

 

[rednecksrule421]

i can get a used transfer case for 100 bucks. do you guys think its worth changin it?

 

[PeterJ]

I'd try maxcr3's recommendation first. I would change it a twice. I wouldn't use Amsoil. I like to use International Harvester Hy-Trans. I would change it, drive the vehicle a few miles, and change it again. You would be out about an hour of time and 3 qts of tranny fluid.

I've replaced a transfer case once (auto shifting '99 Tahoe) and the "rebuilt" one I put in was worse than the one I took out.

You asked

 

[rednecksrule421]

thanks for your time guys, ill try that this week and get back to you on the result. thanks

 

[UxHamby]

my 98 clunks too

My 98 clunks too.

I am told by my independent mechanic, that it is a chain & sprocket in the transfer case. Apparently the chain skips a notch on the sprocket when it clunks.

He didn't suggest changing the fluid but I might try having him do that before agreeing to the $1600.00 repair he talked about. Actually he suggested that I just drive it and see if it gets any worse.

My tranny had a bit of abuse a few years ago, when a wrong size tire was accidentally put on and the front axle was ruined. (I used the spare that came with it from a used car lot but guess what. Wrong size tire was on the spare :-( ) The axle was replaced but the rest of the drive train likely wasn't done any good by the whole affair. It might be related to that but I suspect it is inevitable eventually.

 

[PeterJ]

Wow UxHamby,

I'd be looking to fix that on your schedule. I don't understand your mechanics "wait to see if it gets worse" advice. Does he have a tow truck service too? You could end up with a tow bill when the transfer case blows, plus your vehicle is out of service at an unplanned time. Not to mention, it could take out other parts too, like the tranny output shaft etc.

I would change the fluid first. If you don't want to do it yourself, ask your local quick-lube shop what they charge to do it.

My input is free and worth every penny!

PeterJ

 

[rednecksrule421]

well guys i changed the fluid in my transfer case tonight. the old fluid was brown, no metal shavings in it. took it for a ride up the road and back to warm her up. when i got home i went through some snow and locked it in 4 high. the clunk got worse and i lost four wheel. it just clunk all the time up front now when the front wheels get power. it is a clunking ratcheting sound. i think the case is now dusted.

 

[PeterJ]

I think I hear my Mom calling...

Seriously, time to seriously consider the used transfer case. I wish I new if there was a way to bypass the control and manually lock up the transfer case. Somewhere on the computer I read that the control unit even factors in steering input. If the steering gets too busy it shuts the Auto shift down to let the front wheels free wheel. I realize you were in "4x4" when you tested it. I just don't know enough about the theory of how it operates. I wish I could be of more help.

I don't know if your truck has auto hubs. If it does, you need to check both of them. One bad hub would cause the same problem you are describing. You need to know this before you tear out your transfercase and put another in.

Does it run O.K. on dry roads? Hopefully you can baby some time out of it until you get the answers you need.

I can't believe there isn't more experience popping up here. Maybe you should be in another forum?

PeterJ

 

[rednecksrule421]

on the second gens there are no locking hubs. its all in the transfer case. She runs out good on dry roads. i just did the brown wire mod to deactivate the auto 4wd. till i get it fixed. im gonna pick up a used transfer case on saturday and swap it out if i get time. let you guys knowe how it all goes. thanks for the replys to you all. leter

 

[KPT]

Apparently the chain skips a notch on the sprocket when it clunks.

What what what. If the chain is skipping a notch on the sprocket you have PROBLEMS. I don't think its possible for a chain to stretch that much. 4WD wouldn't work at all. The chain would jump whenever there was a load on it. I'd not go back to that mechanic.

I wish I new if there was a way to bypass the control and manually lock up the transfer case.

There is. Search for the brown wire mod

I don't know if your truck has auto hubs.

Second gens don't have hubs. Not selectable at least. They are always locked.

 

[PeterJ]

What what what. If the chain is skipping a notch on the sprocket you have PROBLEMS. I don't think its possible for a chain to stretch that much. 4WD wouldn't work at all. The chain would jump whenever there was a load on it. I'd not go back to that mechanic.



There is. Search for the brown wire mod



Second gens don't have hubs. Not selectable at least. They are always locked.

Thanks for the good info

 

[JohnnyBoy1102]

Mine kind of makes a clunking noise when i tried to power brake my 98. i think its caused by too much stress on the transfer case or something. it also happens when my tires are spinning in the front. dunno if this is any help.

 

[zonianbrat]

JohnnyBoy, Did you really try to power brake your sport in the Auto mode? Have you done the BWM?

 

[Silver X]

Good luck with the transfer case swap. It really isn't very difficult if you can do it indoors without freezing. Certainly not worth paying someone $1600 to fix it for you.

I've had mine apart a few times...

First, drain fluid. Then remove the front driveshaft, and disconnect the rear driveshaft from the transfer case (TC). You can leave the rear shaft attached at the rear diff. I usually strap it to the exhaust to keep it out of the way. Next, throw a floor jack or trans jack under the trans and remove the trans mount crossmember. Disconnect the TC vent tube and wires. Remove the TC-to-trans bolts that you can get to. Lower the trans a little to get access to the top bolts, then support the TC and remove that last bolt or two. Pull the TC rearward to seperate. Some fluid will pour out from between trans and TC, so have rags ready. Then remove TC from under truck. It only weighs 40lbs or so, so you should be able to lift it out by hand. Use another floor jack to support if unsure. Replacement is the reverse of removal. Make sure you replace the gasket between the trans and transfer case.

*The exhaust cat-back may have to be disconnected from the cat pipe if it is in the way or keeps the transfer case from lowering.

**You might have to jack up the truck and put it on stands if you can't fit under there. Mine's high enough that I can leave all 4 tires on the ground. I just hop on a creeper and roll under.

 

[JohnnyBoy1102]

JohnnyBoy, Did you really try to power brake your sport in the Auto mode? Have you done the BWM?

Wtf is BWM?

 

[Silver X]

Brown Wire Mod. Keeps your transfer case from automatically engaging the front drive. You add a switch into the brown wire to control it yourself.

Do a search here for a better explanation of where it is and what it does.