Andy I had a similar problem with my 98 F150 4X4. I took it to the dealer only to find the clutch pack in the ltd slip was assemble wrong. My dealer told me it was not the first they had come across

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Frosty
"98" S/C 4X4 XLT
Moonlight Blue

 

try having them( the dealer) check the spider gears/ clutches in the rear i have seen alot of them be bad

 

Your rear-end gear lubricant lives in a very difficult environment. On one hand, the lubricant must have enough 'body' to ensure that a film cushion is maintained between the gears -- and at the same time -- it must provide Goldylock's "Just Right" amount of stickshion to let the limited slip work without self-destruction due to over-torque -- yet provide the lubricating and cooling properties necessary to ensure long life.

Additives in Extreme Pressure lubricants include some exotic stuff that, when smashed in the gears, become an additional lubricant.

Some forms of Limites Slip assemblies are in constant compression -- and extreme torques are maintained until that pre-determined level at which the LS is supposed (hopefully) to do the S-part (Slip).

Oils actually get 'sticky' when wedged between something like clutches or cones in an LS Diff. Lubricants which meet all of the other Extreme Pressure criteria don't always also have the individualized property necessary to let the clutches/cones break loose when desired.

Not all axles/gearing are created equal.

Talk with someone who owns a large motorcycle about how (s)he cringes at the first engagement into 1st gear after letting the bike sit all night. The clutches -- even though soaking in oil -- have enough 'stickshion' (my term) that the gearbox gets a real bang of a torque jolt while the clutch pack is jerked loose.

The add-in "friction-modifiers" are added to your gear oil in an attempt to change the property of an otherwise probably satisfactory gear oil so that just enough stickion is reduced so that the parts can move predictibly.

Examples of not working as planned include

a) non-differentiating when lightly accelerating around a corner

b) creaking/slipping/ratchetting under same conditions

c) not enough clamping (known as 'bias') of the LS

d) lubricant failure (the migration of metal between mating pieces)

It is precisely these and other driveablilty issues which keeps some lubricants from making the 'approved lubricant' list of component manufacturer recommendations -- even though those lubricants can admirably pass other benchmark performance requirements.

(Have you noticed that nobody has troubles with non-LS axles?)

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Y2K™ Jim Gorka

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"

 

Well my truck just turned 40,000 and it sounds like i'm having the same problem as everyone else. I can't believe that this is normal, and think that it ludicris that anyone would even think that with the technology of today it would be. You all have good responses, but could anyone tell me for sure what the fix is. Also, has anyone had their rear seals go as early ast 36000 miles? thanks

 

Here's the fix, believe it or not it's this simple and the Ford dealer was completely useless. I got the answer here. Buy a bottle of friction modifier and dump it into your rear differential. It's available from the Ford dealer for less than $10. The results may take a day, but I noticed the problem had gone away almost immediately.

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97 F250 LD XLT Supercab, 5.4 V8, 4x4, auto, towing package, 12,000lb hitch, Load Range E tires, Air Lift, 4 wheel Disk ABS, 3.73 limited slip, K&N FIPK, superchip, payload #2, CD, Navigation System (my very lovely & talented wife), anti-intruder system (our two dogs), real horsepower (Red & Topper, our horses)

 

This really pisses me off. I took my truck in to my dealer @30,000 miles for the works. I.E. oil/filer, tranny/flush/filter, transaxle drain/fill, rear-end drain/fill, lube, tire rotate, yada, yada, yada. I just turned it to 31,950 tonight. It started doing the corner-grind thing on me today, my wife said she first noticed it two days ago. First thing I thought was rear-end, and you guys have confirmed. 3.73 limited-slip. I'll bet my dwindling 401K that the dealer didn't realize it was limited-slip, and didn't put in any friction additive. OK, now the $2,000 question. Since I've been driving it for about 2,000 miles without this additive, what is the damage to my rear-end gears? I'm still under warranty, and if this is in fact a dealer-induced problem, I may want him to fork over a new ring&pinion set. On the other hand, is it worth my while to have them replace it, and have some monkey that doesn't know how to setup a differential properly screw it up worse than it is? Jeez this makes me mad.

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1999 Lariat 4X4 SuperCab Flareside 5.4; Auto, Tow Pack, Offroad Pack, 3.73LS, Factory Step Bars, 17" Chrome Wheels, Oxford White/Silver, Graphite Leather, Keypad Mod., Airaid, SuperChip, ARE LSII Bed Cover, Alpine CDA-855/JBL AMP, Polk dX7's, Custom cat-back exhaust.

[This message has been edited by rons (edited 03-19-2001).]

 

Well, I sure know how you feel. It was the same way with me. I had the dealer change my differential oil and all the other good stuff they recommend and that's when the trouble started.

I can tell you though that I have over 100K miles on the truck now with no apparent ill effects to the rear end.

Based on my experience, you probably have nothing to worry about, but who knows for sure???

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97 F250 LD XLT Supercab, 5.4 V8, 4x4, auto, towing package, 12,000lb hitch, Load Range E tires, Air Lift, 4 wheel Disk ABS, 3.73 limited slip, K&N FIPK, superchip, payload #2, CD, Navigation System (my very lovely & talented wife), anti-intruder system (our two dogs), real horsepower (Red & Topper, our horses)

 

rons, take your truck back to the dealer and at least get the problem put into the computer. You're almost out of warranty so you want that record.

You should take a look at the service records to see if they put in the friction modifier. It should be in the parts list.

At any rate, get your truck back to the dealer asap.

To all. Any rear end noise is NOT normal. I'm on my third F series since 1987 and they have all had limited slip rear ends and none of them has made any noises.

 

If you read back through the thread, you'll see that the friction modifier fixed my problem about 40,000 miles ago. I'm not suggesting that any rear end noise/grinding is acceptable. I'm saying mine doesn't seem to have suffered any permanent damage from the time I was driving it without the friction modifier which was when I was having the problem. I've had no rear end issues since I added the friction modifier.

As a footnote, I had my truck in the dealer again a month ago and had the rear end fluid changed (~100K service). I made the dealer put in a bottle of friction modifier, but they claimed it wasn't a required task and they only did it because I insisted.

???



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97 F250 LD XLT Supercab, 5.4 V8, 4x4, auto, towing package, 12,000lb hitch, Load Range E tires, Air Lift, 4 wheel Disk ABS, 3.73 limited slip, K&N FIPK, superchip, Gibson cat back exhaust, payload #2, CD, lots of dirt and stains, a few dings, Navigation System (my very lovely & talented wife), anti-intruder system (our two dogs), real horsepower (Red & Topper, our horses)

 

Under "Exceptions" (page 33) in my '99 Scheduled Maintenance Guide, Ford says "Rear axles containing synthetic lubricant and light duty trucks equipped with Ford-design axles are lubricated for life..."

It also says to "add 4 ounces of additve friction modifier (C8AZ19B546-A (EST-M2C118-A) or equivalent for complete refill of Traction-Lok rear axle. The rear axle lubricant should be changed anytime the axle have been submerged in water."

There's more in there, but the above are the highlights.

So, I guess the bottom line is, if you have a LS rear end, it says right in the Maintenance Guide that a friction modifier is supposed to be added.

I take that to mean the servicing dealer must put in the modifier and if they didn't then any problems that arises because they didn't use it is their fault.

BTW, it also says to use the friction modifier in the Owner's Manual in the Capacities and Specifications section.

[This message has been edited by Dennis (edited 04-01-2001).]

 

another clunker, sort of the same but different: my clunks happen ONLY when I turn, and only one clunk per directional turn. one left turn, one clunk and then fine till I make a right turn, then one clunk. any ideas?
this on a 98 xlt 4.6 180k miles

 

Old thread I just found. I recently had a Yukon diff installed. They advise to use 80/90 NON synthetic and 2 bottles of friction mod. Said the grumble is common when using synthetic in a limited slip.