2004 F150 FX4 97K

When acclerating and turning from a stop
(like making a left hand turn), the rear end kind of stutters
and then hops/bumps and goes smooth. One wheel
turning faster than the other? Researching this site it
sounds like the bad clutch packs TSB. Question:
how long can I drive with this problem before I mess
something else up seriously on the truck? My ford dealer
quotes $1200 for the repair, and I would like
to postpone the expense.

 

Stonetrade, I had that problem @35K. Ford replaced it under warranty. I changed the fluid and added the friction modifier after about 5K just to get rid any break-in material. I added Lucas oil treatment to mine also. I have 79K now with no apparent problems, knock on wood.

 

If fords quoting you 1200 bucks for just new clutch packs thats rediculous...

The rebuilding of the limited slip is about 200 bucks at best at a mechanic, now if you have other problems in the rear end, thats a different story.

You should be able to have a new (not rebuilt), much better limited slip (an eaton or tru trac) installed for about 600-700 bucks

I'd ask what parts they're replacing, at the 1200 bucks they're quoting you i'm wondering if they're rebuilding with new bearings, gears, and axles....which probably aren't needed.....

 

what about grabbing the axle out of a wrecked truck?

 

I would try changing the rear end oil and add new friction modifier to see if that helps out any. You won't break anything by doing this. If the shudder goes away you're home free. If it still shudders, then you may need a new clutch pack. You should be able to have an independent shop rebuild the clutch packs for in the $500-$600 range parts and labor.

 

If you have to replace them I would agree with Ryan and get an Eaton.

 

It doesn't sound like the clutch packs are 'bad' because they are 'grabbing'. Add friction modifier to get them to 'slip'. Take the opportunity to replace with synthetic fluid.

 

Try buying a bottle of motorcraft XL.3 and put it in and see if that solves the problem.

 

i had my rearend done in my 04 screw and when i was squareing up with the casher t noticed a sheet of paper she had and with parts and labor it was just over $2000...only costed me $100 tho

 

Thanks for the idea. Where do I find out which oil and modifier to use?
Would Ford tell me?

 

The official oil type would be listed in the owner's manual. The additive is simply called Ford/Motorcraft limited slip additive. This is a "friction modifier" which basically makes the lube more slippery so the limited slip just slips more.

Edit--here is the TSB, and they are saying to use 75W-140 rear end lube even though 75W-90 may have been the original recommendation https://www.ford-trucks.com/tsb/full...php?tsb=06-4-4

For the F-150, Ford says that you only replace the clutch packs and that it takes 3.2 hours of labor. Sounds like less than $500 to me.

Chattering clutches in the rear axle are not really a major problem, although they can be annoying. All this means is that the limited slip unit is trying to grab; I don't think it's gonna hurt anything else unless you're running lots of torque thru the rear axle.

Still, with the mileage you've got, it would be a good time to drain the rear axle and replace the lube...there is bound to be some work friction material floating in the lube.

Before you spend big bucks on the unit, go to an axle shop and have them replace your factory limited slip with something like an Eaton posi unit--I have an Eaton posi in my 2002 E150 van and it works great....and by the way, my Eaton unit has chattered a bit since it was new in situations like you describe (tight turn on wet pavement with a little kick to the throttle).

George

 

IF it needed axles, bearings, seals, gears, limited slip and labor maybe....

but for clutch packs you don't even need to pull the axles all the way out if you don't want to....its no where near 1200 bucks

 

Cost $900 to have it done in my '04. I wish I had never fixed it because I ended up trading it for an '09 a couple months later.

 

maybe the local stealership was wanting to overcharge ford or somthing...because thats the same axle on my truck as when i bought it

 

I bought synthetic oil and friction oil from
my ford dealer and had my mechanic put it in. $60 for the oil,
$40 for the service, and the problem has disappeared.
Thanks for the help!