My wife drives a 2000 Expedition, 5.4ltr, I believe its the all time 4 wheel. Even though theres a switch inside for A, Hi, and Lo

Anyways she's having a problem with the front end. More noticeable on turns and harder acceleration. Sounds like something is loose, its bangs but then when you get up in RPM's it tends to go away. Almost as if the tire has a flat spot on it.

I've had the truck up on jack stands and wiggled everything. i'm not seeing a worn tie rod,or ball joint. They all appear fine along with the other steering parts.
She's get a heck of a squeak out of it well when going over speed bumps.
Any thoughts as to what I'm missing?

thanks

 

You didn't mention the miles on it or if there has been any work done on the front end.
From your description I would hazard a guess that the front end needs to be looked at by a pro. I suspect ball joints, control arms and sway bar links.

 

Shocks were not mentioned, a fresh set on my '99 cured the noises. I did check ball joints as they wear out, but mine had no movement.

BTW, the 4wd system is not all wheel drive or full time 4wd. It has an automatic setting that engages the part time 4wd transfer case when a speed difference is sensed between front and rear wheels. The truck is rear wheel drive, and there is no center differential as required by a full time system.

 

The truck has 140K on it,
I replaced inner/outer tie rods this spring. Shocks are about 4 years old. i just replaced the backs and figured I better do the fronts as well.

I never did understand how the 4x4 stuff worked on this thing. Is there anything in the anti slip that can cause that grinding noise on turns and accerlation?

I did some searches and came up with the possiblity the CV half shafts might be worn. What do I look for to test?

Ball joints and control arms I comfortable with and have gone over those several times looking for worn parts but its tight.

 

The shocks could definately be shot in 4 years time. At the very least make sure the shock mount bolts are all tight. If they are even a little loose you will have a clunk.

The grinding you hear is most likely from the rear end. I am assuming it has the LSD, if so a bottle of friction modifier should cure the noise. CV joints tend to make clicking noises when they are shot rather than grinding, and usnless you have it in 4x4 or are on a slick surface, there is no power going to the front.

To test the CV's, first make sure the boots are all intact. If they are cut and leaking, the boots need replacing. You can select 4HI and do some back and forth turning while applying some throttle. If the CV's are bad, they will "click" or make a ratcheting sound. If you hear grinding from up front, wheel bearings are most likely the cause.

I am betting a rear diff service will cure the noise you describe though.

The 4x4 system on the Expy is essentially the same as your pick-up. The major difference is that a computer monitors wheel speed sensors. When the computer senses a front to rear difference it engages the front drive until the difference goes away. The t-case does use a progressive lock up for the front so keep the transition smooth, but otherwise is very similar to any standard old school 4x4 system.

 

Thanks guys for all your ideas so far. I gotta say this forum has always cut right through the BS and get right to finding the solution.

So tonight I put the wife in the drivers seat in the drive way. Had her put it in 4 wheel and drive sloow and turning the wheel. She had a bit of a problem getting it to move but she got it and I heard the "popping" noise. Didn't know where it came from but good I heard it!. Did it again, and watched very carefully.... S.O.B.... I watched the back tire lock up ...pop...and do it again. Its not the front. I would have sworn thats where it was coming from. Upon further inspection I noticed the differential cover is leaking...fresh oil.

A couple of questions.
I'm gonna remove the cover to inspect and reseal. Hopefully I can save it. When making the gasket I normally use Right Stuff, Is that good to use?

Recommendations on what differential oil I should use?

Naturally I have to dig into this further to make sure the gears and shafts are ok.

 

Now it seems that you just have dry or sticky clutches in the dif. and the new lube should make it all better.

 

That a normal reaction when turning in 4WD on dry pavement. I'm not saying that you haven't found the problem, I'm just saying don't get your hopes up. If the problem was the rear differential you'd have the noise when you're in A4WD and making turns. Another test you should do is remove the fuse for the A4WD system to prevent the front from engaging and then see if the problem still exists.

 

That is normal for the truck in 4 Hi turning on dry pavement. You have locked the front and rear together with the t-case. The tires are not able to turn the same speed so a tire in front or back must "slip" or something breaks.

I agree with alloro, I do not think you have found the problem. Aren't we talking about a couple of different problems though? The OP was about a noise in the front end over bumps. Later the discussion turned to a grinding in the rear end. The diff service may help, or likely cure the grinding noise, but doesn't acount for the rattle over bumps. OR did I just misunderstand somewhere?

 

No you didn't misunderstand. I do believe that there are a couple of problems I'm dealing with.

As of tomorrow I will have the truck for the day so I can start with the repair of the differential and shock replacement.

That should eliminate the easy items.
The biggest problem she is having is the noise when making a turn from say an intersection and upon acceleration she gets a noise. She describes it as grinding. I feel is more of a grabbing,popping,or clicking type of noise. Once it gets going it goes away.

 

I think the diff change will fix the binding / grinding. My dealer uses two bottles of modifier on higher mileage vehicles, so you may want to consider that. An extra $5 to make a $1200 assembly work smooth.

 

The popping, grabbing and snapping sounds are the classic symptoms of a Traction Lock differential in need of a fluid change and some friction modifier. After changing the fluid you will need to make a number of both right and left turns to work the new fluid into the clutches so you won't have instant quiet immediately,it's going to take some miles for it to get like it was when new.

 

Have a quick question. When refilling with oil and modifier do I use the hole for the ABS sensor? i think I do since i can't find a fill hole.
thanks

 

The fill hole is on the driver's side of the differential in front of the axle. You need to use the correct fill hole unless you pre-measure the amount of fluid going in. Using the proper fill hole prevents you from overfilling it.

 

Guess that means he didn't check if he could get it off before he drained it!