40 XLT with 4.10 slip Axle - Rear-end chatter on take-off

Hello all,

I did a search on this, but came up with a lot of varied posts from the last 12 years, so I'm hoping I might be able to get a fresh perspective on my issue. If there are some post that might be related, I'd appreciate the links. Anyway here's my issue...

I have a 2004 Sport-trac XLT with the 4.0 liter V6 SOHC engine and the 4.10 Limited Slip Axle option. I purchased the truck NEW in July 2004, but don't use it much-- it has less than 25,000 miles on it. Last summer I started to notice a chatter in the rear of the truck (something slipping) when I'd take off. If I pulled out very slowly, it wouldn't be as dramatic, or at all. It also seems worse when (the truck) is cold. After it warms up, it's not as bad. Then sometimes (usually when it's hot in summer) it doesn't do it all.

At first I thought it was low on transmission fluid, but I check that and it was fine. I had to take it in a few weeks ago (to the dealer) for a state inspection, do I ask them to check it out while it was in. The service manager called me and said it was either a) (get this!) the "break dust covers", or b) rings or shims in the rear end that need replaced, which was going to cost over $1,000 to repair.

I put the break dust covers on the truck when I first purchased it 12 years ago, so I said unless they didn't put the wheels back on correctly, It certainly wasn't those. But since that was his first "guess", I decided not to let THEM do ANY work until I got a second option. Maybe it was a legitimate idea, but I thought the dust covers answer was pretty lame. All he had to do was take the truck out for a ride and he would have realized it wasn't those. And THAT was the SERVICE MANAGER making the suggestions! Either simple or very bad-- no middle ground.

As you can guess, with less than 25,000 miles on a 12 year old truck (23,296 actual miles today), I don't use it much. Just an occasional trip to town or to tow my (small) boat a mile to the launch ramp in the summer. So I'm a little skeptical that it would be anything major, but I guess it could if you just go by the age of the truck. But if it was major, it would be a little upsetting at those miles (based on the national average of 12,000 miles a year, the truck spent 10 of the last 12 years just sitting in my garage!).

Anyone have any suggestions (other than to seek out a second (more thoughtful) opinion)? If you'd like any additional information, I'd be glad to submit it.

Thanks...chugbug

Are you going straight, or turning, when you hear the noise? Have you had the rear diff oil changed recently?

Thanks for replying to my inquiry Koda2000!

First I should clarify that it's actually more "feel" than actual noise. I referred to it as "chatter", but it something I feel, like something slipping in the back end of the truck. Maybe calling it a SHUDDER would be more appropriate than chatter.

Turning... I know for sure that it does happen when I'm turning--such as making a turn after stopping at a stop sign or traffic light. And I know for sure it happens when I turn RIGHT, but can't recall anytime when I specifically noticed it on a left turn or even pulling out straight. I make several right turns between the house and leaving the complex I live in--at least three stops and then right turns and it would happen during each one.

I'll have to take it out for a test to see if it happens turning left or going straight. If it does happen only during right turns, does that help to narrow it down?

Rear Differential oil change... NO. It has never been changed. According to my owners guide it has SYNTHETIC oil and it says "Rear axles containing synthetic oil are LUBRICATED FOR LIFE".

HOWEVER, it also says that it should be changed "anytime the axle has been submerged". I mentioned in my initial post that I use the truck for towing my boat during fishing season. But I can't see how launching the boat would have ever submerged the rear end enough to get water in it. I would have had to back up far enough to get well above the exhaust pipe, and I don't think I've ever had the back end in the water that far. But I guess it's possible I could have at some point over the 12 year period. It's a small boat, but the ramp is pretty shallow. I'll try and remember to see how close to the water line it gets the next time I take it out (which hopefully will be any day now).

Based on that possibility though, would changing the oil help? If so, should I replace it with anything other than the recommended? It only lists one type--Motorcraft SAE 75W-90 Fuel Efficient High Performance Synthetic Rear Axle Lubricant--nothing about any additional or optional axle types (such as my 4.10 limited slip).

Axle friction modifier... I saw in one of the post (here) during my search where someone recommended adding a "friction modifier". Would something like that help? If so, and it's also recommended that I change the oil, should I add this before (just to try it out) or after changing the oil (adding it permanently)?

Thanks again for the assistance!

Check the rear universal joints or replace them. They might be dry.
Dave P

Also check for a dragging rear brake caliper. If the "feeling" happens when you're going straight, it's not the rear diff. The reason I asked if you'd changed the rear diff oil recently is that you will get a "chattering" when turning if you didn't add the LSD additive.

Ford transmissions also tend to develop a shutter when the trans fluid is past it's service life. When was the last time it was changed?

With you're low miles, I'm not thinking u-joint, but you never know.

Are you sure it's the rear?

I have an '05 ST, and i notice a shudder when i turn right, but only at full lock, and it feels like it's the front. I haven't had a ton of time to dig in to this yet, so i'm anxious to see how this thread develops.

I know it's not a ton of helpful information, but you are not alone in this observation.

I don't know how these limited slips compare to the old Traction Locks, so this may not apply. I swapped a used Traction Lock from a car that hadn't been driven in a long while into one of my Rancheros. It operated a little rough from lack of use, so my ace mechanic friend and I went to an empty parking lot and drove around in tight circles for about 20 minutes, laughing the whole time about how stupid it probably looked. We'd go around to the right for awhile, then left for awhile, back to the right, etc. The idea was this would get the gear oil circulated into all the places it needed to be faster than it would have in daily driving. Worked like a charm. The roughness was gone and never came back.

Since your truck has been driven so little over it's lifetime, this might be worth trying.

Hi Guys! Thanks for all the input! It gives me a few things to mention when I take it to someone to have it checked out. I also think now that I have a few specific things to consider, I'll take it out a few more times to see if I can narrow down where and when I feel it before I take it anywhere else. But I should probably wait now until it warms up again before taking it out. The temps are back down in the 30's around here (in PA) again.

The idea that it's the rear end oil isn't circulating enough seems to make sense since I don't drive it much, and when I do, it's usually only for a short trips (less than 10 miles). Also since it seemed strange that it didn't crop up until after I started using it LESS frequently. So it sounds logical anyway. AND it will be fun to test out the theory!

Based on my conversation with the service manager at the (Ford) dealership (where I purchased it), I'm not going to do anything with it anyway until I get a second opinion. We have a local guy that's been servicing our other vehicle (2002 Jeep Liberty) and he's been pretty good at diagnosing stuff. After my conversation with the service manager, I just don't have much faith in the dealerships diagnosis.

If I sound apprehensive, it's because we've had a similar experience with our 2002 Jeep Liberty and the Jeep dealership. A different problem, and different dealer, but we got the same type of suggestion of throwing a lot of money at the problem and hope something along the way would fix it. The heater wasn't putting out any heat when it started getting cold. AND it happen to be not long after they replaced the radiator (after an errant stone punched a hole in the old one). They wanted us to spend about $2,000 to pull out and replace the heater core (they wanted $1,200 just for the core). We decided to take it to a local guy for a second opinion before doing anything. He confirmed my suspicion that it could just have an air block somewhere in the heater line from replacing the radiator (that the dealership quickly dismissed). For just $75, he back-flushed the system (twice) and replaced the fluids (which he said the dealership didn't do). The heaters been fine ever since--we've had good heat out of it now for the past two winters.

I'm sure it's not that way everywhere, and there are good service guys at most dealerships. But unfortunately it doesn't seem to be that way here, or at least with us. When ever we have a problem, it never seems like they put much thought or time into making their diagnoses. They always seem to come back to you with the most expensive repair, that most times requires at least TWO (and sometimes three) separate trips and more money than was initially quoted until they get it resolved. I always thought they were suppose to be the professionals when it came to the vehicles they sell and would (should) know the most about them. But it seems to be the opposite these days. The local guy can usually pinpoint the problem much better, and he can usually can fix it for much less and do it on the first trip.

Thanks again for the assistance! I'll try to remember to report back after I take the truck out for a few more test runs.

When my mechanic friend was working at a Ford dealership a few years ago, he told me the younger guys - essentially everyone else at the dealership - just knew how to change the parts the computer told them to. They didn't know how to actually FIX anything. When they needed to FIX something, they'd bring it to him. Of course when the dealer needed to cut costs, he was let go because he was getting paid more. He was also their best mechanic.

Replace rear end oil with 75-140 oil and 2 4oz containers of friction modifier from Ford dealer. I can almost promise you it will fix the issue. There is a tsb on this for 02-04 vehicles with the 8.8 and 9.75, they put 80-90 in them from the factory for some reason.

Thanks! I'll mention that when I take back in to someone! Any chance you'd have the number and release date for that TSB? Is there a place online that I can look it up, or is it something only Ford service employees have access to?

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UPDATE 4/14/16 - I found a website called "FordProblems.com" with a list of all the service bulletins: http://www.fordproblems.com/tsbs/Explorer/2004/

They didn't have the Sport Trac listed separately (that I could find), just EXPLORER. But I found these two TSB's that BOTH have a reference my problem (they didn't list any fixes, just the problems):

Description: LIMITED SLIP AXLE CHATTER, SHUDDER, BINDING SENSATION, OR VIBRATION DURING LOW SPEED TURNING MANEUVERS. *TT

TSB #03198 - Reported September 6, 2004.
TSB #06216 - Reported January 1, 2006.

It's a little irritating that BOTH of these are VERY OLD TSB's (10+ years!). If I could find them, why didn't the service guys at the FORD DEALERSHIP? I specifically ask them if they're were any issue reported, and he told me there wasn't. I'll take the TSB's along with the oil change recommendation to the new guy I'm going to have look at it.

Thanks again everyone for the help!

Did you change the rear-end oil and add the friction mod? Did that help?

I have the same issue, obviously more miles. but thinking that when they changed my rear left axle seal, they didn't put the modifier in it.