OK, this one is a bit hard to explain, but I thought I'd throw it out there to see if anyone had any thoughts.

The truck in question is a 2009 F150 5.4 3.73LS 4x2 Screw 6.5', currently with 15K on the clock. I have several symptoms which may or may not be related.

Since day one, it has suffered from a "chatter" in reverse - shift into reverse and give it some gas (nothing excessive) and it feels like the LS kicks in. This is especially prevalent when turning.

From the first oil change, the shop doing the work has commented on excessive metal in the rear diff. They've checked the diff fluid at each oil change (2K, 7K, 12K) and have commented on metal shavings on the plug as well as the overall appearance of the fluid, which is gunmetal grey in color with a "gritty" feel.

In the rain, if I get on it pretty good, occasionally I'll get a significant wheel-hop issue that will jar your teeth out.

Finally, at some points, it feels like the power comes on in "stages". Let's say I'm cruising about 35mph and lean into the throttle a bit - enough for a downshift and for the engine to climb up to 4K or so... I get a weird "jerky" sensation, like the power isn't coming on smoothly. The engine RPM doesn't bounce or do anything weird, so I'm thinking it would have to be in the driveline somewhere?

I've talked to my dealer, who wanted me to drive it for awhile and see what happens. They claimed that some metal on the plug initially was normal, and that there was a reflash available for some transmission shifting issues, but I'm not sure what I'm seeing/feeling would be caused by a reflash.

My gut feeling is something wrong with the rear diff, for a start... maybe no friction modifier from the factory, causing the LS to engage too frequently and thus burning up the clutch packs?

 

Interesting. I feel/hear a strange vibration comming off that gas after getting on it a little. I always suspected it was the rear diff. Would like to hear what you find out. Mine is not something I am too concerned about but does worry me sometime.

 

Kinda sounds like a lack of friction modifier to me... I had a shop change the gear oil in my 2000 (actually a Ford dealer!) and they neglected to add the modifier... differential made kinda the same sounds you are explaining. Try getting the gear oild changed and be sure to add the modifier. Some metal should be normal because the gears are still wearing in, but after 15,000 miles they should be pretty well broken in. Did you tow with the truck or anything before about 2,000 miles?

 

So far I've towed once with the truck, at about 5K... that was a 16x7 enclosed cargo trailer with a very light load over fairly flat terrain.

I've never cracked one open before - what color should the gear lube be in this diff? Should it be brown like motor oil, or is gunmetal grey correct?

 

I have an 09 Platinum 4x4 and have similar issues. The last service I told the dealer to check freeplay or slop (whatever you want to call it) in the rear diff. They checked and did find excessive freeplay. Basically they told me to continue to drive the truck while ford figures out what action to take. They did mention a possible replacement of fluid with another type to try and solve the problem. The transmission surge is another issue that I have also experienced and will let them know about next time I take it in. I am not real thrilled with the way the transmission shifts, it seems to slide or slip into the next gear. Maybe they can fix that with the reflash you are talking about.

 

You know all the money that we spend on these trucks you would THINK Ford would have worked the bugs out. But OBVIOUSLY they sure as hell didn't !! I'm trading in my 09 Lariat Screw on a 2010 Lariat Screw. The truck was factory ordered and should hit the dealer on Dec. 14th. I hope I don't have all these damn problems !! I think it's called a CLASS ACTION LAWSUIT !!

 

I get that same chatter too, just in reverse every once in a while.

On my old 04 truck, it did the same thing but only when going forward/in drive. at the time, the dealer replaced the clutch packs and it was fixed. I guess I'll have to ask them about my 09.

 

Trading an 09 for a 10, Don't sound to logical to me.

 

And no one opened it up to see what's happening?

FWI, fine metal shavings are normal in a diff. Years ago the manufactures started putting magnets in the plugs to keep the shavings in check. When diffs wear in, gear lube becomes a shade of grey. But feeling gritty is an issue. At the very least, a gear lube change is in order.

 

I say it wouldn't hurt to add some friction modifier. If the chatter goes away, you are good. If not, you may have trouble. My clutch packs went out in my 2000, so I just upgraded to an Auburn Limited slip while I had the rear end apart. I also replaced the ring and pinion, seeing as how it had to be taken apart anyway and there where about 110,000 on the gears already.

 

Dealer told me to drive it for awhile and see if it continued or was just related to break-in. I'm on vacation this week, so I'm going to get it into the dealer and have them pull the cover and look at it (which should get a fluid change with friction modifier). They're also going to reflash the TCM to address the harsh 1-2 shift. Once that's done, I'll reevaluate...

 

I have FX4 4x4 supercrew with the 3.73 Locker rear end. On some occasions the transmission does shift hard. But of more concern I just noticed the transfer case is seeping fluid from the rubber ring around spindle that exits the rear of the transfer case to rear UV joint. I noticed this from spots on my garage floor. I was curious if anyone else has had this happen.. It's going to the dealer Monday. I was reluctant to buy the new model with the new transmission, but did. My 1999 I had not one problem with 105000 miles when I sold it.

 

Fortunately the running gear has a 5 year 60,000 mile warranty.

Don't do anything to the truck yourself and certainly don't allow a non-Ford dealer or unauthorized service center work on it outside of engine oil changes and tire rotations.

I think I'd become a little more assertive with the dealer and make them open the rear diff and re-lube it to factory specs. This may solve it.

On a similar note, I bought my '04 Expy new and it has the 3.73LS axle. From day one, I could feel a vibration coming from the seat. Took it back and they had to rebuild the whole damned rear end with only 800 miles on the clock. I was pissed about the truck but thankful that I pushed them to get after it.

Tim

 

Yep, I'll be calling them Monday and getting something set up. The oil change place pulls the plug to check the fluid level (and pimp a rear diff service if they think they can get away with it) but that's all they've done.