Hi All,
I have strange prob with my rear diff.When I turn at low speeds I get an shutter sometimes, I know please don't beat over the head about the shutter I know it just happens. But when I let about half of my ponies out of the stable, the diff starts to lock together.I geuss what I'm wondering Is the diff torque sensitive to where more hp=tighter diff?

 

need a little more info, which axel do you have (code on door jamb) is it Trac Lock (limited slip)

 

He said Fx4 so I would say limited slip

 

I have checked the jam and it said b6.

 

Yup, your right just making sure, B6 comes back as 3.73 LS

Did you have your diff worked on lately?

 

so is my theroy correct?

 

if you are on slightly slippery surfaces (wet roads), with no weight in back and get on it in a turn, the LS may just be doing what it is ment to do, lock in order to give better traction, i would guess this would most likely cause a small shutter. just my opinion

 

Is the tightnes of the diff dependent on the input torque?

 

no its not. there is a TSB for updated clutch packs. that is what you need.

TSB
06-4-4 LIMITED SLIP AXLE CHATTER, SHUDDER, BINDING SENSATION, OR VIBRATION DURING LOW SPEED TURNING MANEUVERS

Publication Date: February 16, 2006

FORD: 2002-2004 Mustang, Explorer, Mountaineer
2003-2004 Expedition
2004 F-150
LINCOLN: 2003 Navigator


This article supersedes TSB 06-02-16 to update the Service Procedure.

ISSUE:
Some 2003-2004 Expedition, 2003 Navigator, 2004 F-150 vehicles equipped with a 9.75" or 8.8" limited slip rear axle, and 2002-2004 Explorer 4dr, Mountaineer, and Mustang vehicles equipped with 8.8" limited slip rear axle, may exhibit a chatter, shudder, a binding sensation, or a vibration during low speed turns. On 4X4 vehicles, the sensation may appear to be originating from the front axle or the steering gear.

ACTION:
First verify the condition. On 4X4 trucks ensure that the vehicle is in 2WD, to isolate the rear axle. On all vehicles, turn the wheel fully right (or fully left) and then accelerate the vehicle. If the condition is verified to be in the rear axle, replace the limited slip clutch pack.

SERVICE PROCEDURE

CAUTION: INSTRUCT THE CUSTOMER NOT TO TOW WITH THE VEHICLE FOR 500 MILES (805 KM) AFTER THIS REPAIR, TO ALLOW THE AXLE TO BREAK-IN PROPERLY.



Order and install the appropriate clutch pack, follow the instructions detailed in the Workshop Manual.

6L1Z-4947-A (9.75" limited slip)
F5AZ-4947-BA (8.8" limited slip)
NOTE: INSTALLING A CLUTCH PACK INTO AN INDEPENDENT REAR SUSPENSION (IRS) AXLE IS DIFFERENT FROM INSTALLING A CLUTCH PACK INTO A SOLID-BEAM AXLE. BE SURE TO FOLLOW THE APPROPRIATE WORKSHOP MANUAL PROCEDURE.



INSTALLATION TIPS

Be sure to install NEW circlips and halfshaft/wheel end nuts on IRS rear axle (not included in the service kit)
Soak the new clutch packs in Additive Friction Modifier (XL-3) for fifteen (15) minutes prior to installation
For IRS axles, the half shaft seals need to be replaced. Expedition and Explorer/Mountaineer applications should use seal kit part number 5L1Z-4A109-A. Removal of the half shaft excluder seal 1L2Z-1N013 may be required, if equipped, to facilitate re-assembly
Refill axles with 4 oz. Additive Friction Modifier (XL-3) and the necessary amount of Rear Axle Lubricant (XY-75W140-QL), regardless of the axle lubricant system originally used in the axle. Fill to capacity recommended in the Workshop Manual
NOTE: AXLE FLUID REQUIREMENTS HAVE BEEN CHANGED. ALL VEHICLES BEING REPAIRED BY THIS TSB MUST HAVE REAR AXLE LUBE XY-75W140-QL INSTALLED, IN PLACE OF XY- 75W90-QFEHP. AS PART OF THIS REPAIR, CHECK AND REPLACE IF NECESSARY THE CURRENT XY-75W90-Q"FEHP" METAL TAG, WITH A NEW 75W140 TAG (F3TZ-4121-AA). ADDITIONALLY, REMOVE THE MULTI-COLORED LABEL WHICH IS LOCATED ON THE RIGHT SIDE AXLE TUBE, OR BLOCK OUT ANY/ALL "FEHP" OR "75W90" REFERENCES ON THE LABEL.



PART NUMBER PART NAME
6L1Z-4947-A 9.75" Axle Clutch Kit
F5AZ-4947-BA 8.8" Axle Clutch Kit
5L1Z-4A109-A Axle Seal
XY-75W140-QL Rear Axle Lubricant
XL-3 Additive Friction Modifier
W710084-S439 Nut (Wheel End)
2L1Z-4B422-CA Circlips (for 9.75")
1L2Z-4B422-BA Circlips (for 8.8")
F3TZ-4121-AA Metal Tag - 75W140

 

The new clutch pack ain't free - you can try doing a lube change, use synthetic 75W140 and a bottle of modifier.

 

thanks for the reply fellas,so the tightness of the diff is constant no mater how much torque I put on it? Ok, Well what about the time me and my buddys did a little wheelin and flexed the truck with one of the rear wheels of the ground and in 2wd in would just spin (the lifted tiire)just like no ls?but if I'm pulling out of a stop sign to the left or right with enthusiasim the inner tire sings with protest?I'm starting to gett confused?Any help much apprec iated