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This is the thread I started this problem with. https://www.ford-trucks.com/forums/1...p-or-jerk.html and https://www.ford-trucks.com/forums/1...r-bearing.html. I took it to the dealer today and had the shop foreman ride with me. It is only jerking when it is turned, even ever so slightly. He said it felt like the limited slip binding. So I asked, "what did you do wrong? Did you put the wrong fluid or not enough fluid or what?" Well he couldn't answer and said the service writer and technician would let me know after they look at it. So it had no issues, then I get them to fix the leaking pinion seal and rear diff cover, and now it jerks from the rearend. Does this sound like it could be the problem? If so what did they do wrong?
If you have a limited slip rear end it sounds like they didn't add the friction modifier to the the rear end oil. The modifier is necesary to let the clutch packs slip in corners since they are now turning at diff. speeds.
You are so helpful. I was just searching for info on this site for it. That is what it sounds like to me. Could it have damaged anything in the few hundred miles I've driven it since they worked on it? I can't wait to hear what type of nonsense they come up with. One thing is for sure, since I have found a good local independent shop, it will never go back to the dealer for anything. This place is a joke. The receipt is in the truck but I think they charged me something like $150 for 6 quarts of fluid to go back in it.
I doubt that it hurt anything. I would just tell them to drain and refill with the correct oil and modifier. If they say the correct oil was used tell them to prove it.
Looks like most of the threads I find suggest adding limited slip friction modifier in increments of 2oz until the chatter/shutter/shake is gone. If I don't get the right answer from them I guess I may stop and get some and go that route.
When I did mine I used the Mobil 1 stuff that already has the modifier in it.
I got a little chatter on corners so I added a bit more till is was quiet. I think
that was about 2 oz total. Where I really was able to hear it was on a section
of road that had a series of "S" curves. So it was working the LS and it was
making noise. So add a bit and go drive the road till it stops.
So you used the mobil1 with the modifier and then added extra modifier untill it quit makeing noise. Is that correct Yahiko, just clarifying what I think you mean.
The answer is, apparently it was. They confirmed it was the LS making it "shudder". "Added one additional bottle of friction modifier to rear diff fluid. Test drove op normal". So I guess this mystery is solved.
They said one additional! For all you know it was the first?
Exactly. I asked the service adviser if they forgot to do it the first time and he just said, well it was on the invoice the first time. That's why I'm done with the dealer. I can talk to the guy who actually is working on my truck at the independent shop.
So you used the mobil1 with the modifier and then added extra modifier untill it quit makeing noise. Is that correct Yahiko, just clarifying what I think you mean.
Yes that is correct.
It really did not need that much but made a BIG difference in the "S" curves.
No more thunk and bump.
You are so helpful. I was just searching for info on this site for it. That is what it sounds like to me. Could it have damaged anything in the few hundred miles I've driven it since they worked on it? I can't wait to hear what type of nonsense they come up with. One thing is for sure, since I have found a good local independent shop, it will never go back to the dealer for anything. This place is a joke. The receipt is in the truck but I think they charged me something like $150 for 6 quarts of fluid to go back in it.
If your receipt says 6 quarts, ask them where they stuffed it all? I think it is more like a 3.5qt fill...
Maybe they'll give you some money back, that would be nice...
I found the receipt. 5 quarts of xy-75w90-qls oil for $90. So there is price gouging at its finest. No mention of the limited slip modifier on the invoice so apparently they didn't add it. I googled the oil and it specifically states that some LS differentials need the modifier "Note: For a complete drain and fill, some limited-slip axles require addition of Friction Modifier, Part Number XL-3. Refer to the Workshop Manual or Owner’s Guide". So I guess it was too much trouble to look it up. It is Rusty Eck Ford in Wichita. Their shop is a joke and it will never go back to them. This isn't the first time they have provided terrible service on my truck.
