I am close to needing to replace/repair the rear differential on my 2000 F-150 4X4 Lariat w/5.4L. A service station that I trusted to change the fluids in my truck did not put the friction modifier in and damaged the mechanism before I figured out what had happened.

Anyway, it has been about a year of chattering and clunking and it is getting worse. Anyone have an idea what the failure mode will be for this when it goes? Lock up? Free spin? Explode?

I have taken down these numbers off of the differential. Can anyone tell me what all of this means? 5919F & 155 975 9M29

If I want to replace the whole pumpkin with a used unit are there just certain aspects of this diff. that I need to match exactly and others that can differ? Or do I need to match them exactly? Can I replace just the guts in this thing, and if so, what do I need?

Any help form you gear-heads out there will be greatly appreciated!

-Alan

 

Ya know, you can take all of the information off the axle, as well as any repair estimates, and throw them out the window.

This was a case of their negligence, and you shouldn't be responsible for damage they caused. If I were you, I'd take it to your ford dealer, explain to them what happened, and see if they can test and prove there is no friction modifier in the fluid. If they test it, and find no friction modifier, then you go after the shop that did it. They are responsible for repairing the damage, not you. Proof from the dealer that there was no friction modifier, combined with a reciept or some proof that they changed the oil, should be enough to force them to be liable for the damage.

Good luck!

 

Good advice, I know. But it is too late for this. I lose here because yoo much time has gone by and too many actions taken.

I took it back to them and they put modifier in after the fact and it did slowly get better so I thought maybe it was OK. But it was not.

I just need to know how to best go about fixing the darn thing now. Next time I'll be smarter.

 

I've never done much with the rear ends, but I've gotten a lot of information from this forum. What I've come to understand is that it's best to have a good shop do the work, as I've heard not getting things exactly right will cause it to go bad again in short order. You may be able to find a used axle off of ebay, and that may be a cheaper way to go.

For an example, go to ebay, and pull up item number 7939745145. This one is only $210 for the entire axle.

You probably have the 8.8 rear diff, so I believe any ford 8.8 rear should work, but I'm not sure.

What records do you have with the service. Can you prove they added the friction modifier after the problem surfaced? If you can, that should be more than enough.

I'm just frustrated about all of these shops that do bad work, and get away with it. Someone there didn't know what he was doing, and caused significant damage to your truck. It's not your fault in any way, and they should be responsible. the way I look at it, even if it's not clear cut, if they made a mistake, they need to fix it. IMHO, if they give you any problems, I'd call a lawyer.

 

I have a 9.75 rear end with a 3.55 ratio. And I understand now theat the carrier/locker for my truck is the same all the way back to 1997 and up to 2004. I see several of these on Ebay as well. I have been told that if I have slipping going on that I probably have teeth missing off the ring/pinion. I am thinking and hoping that this is not the case as I do not have any clunking and grinding going on, just slipping pretty much.

 

When do you notice the slipping?

 

Around corners and from a dead stop under load.

 

Chattering around corners is usually caused by the limited slip clutches which are probably shot from not having any friction modifier. There isn't really anything in the diff that can cause slipping when starting off in a straight line without major damage and it probably wouldn't drive if it was that bad. In a straight line the limited clip clutches really aren't doing anything, just going along for the ride.
If you had teeth off the ring and pinion you would have horrendous noises and it probably would have blown up by now.