Blew seal and differential is destroyed thinking of replaceing whole rear end assly.

Have you had your tires balanced? have you had an alignment? do you have any broken suspension parts front or rear? Is your drive shaft bent? balanced? What makes you think changing differential assemblies will stop the 'shaking'?

if your talking about the rear brakes its probably the differential axle seal that is leaking differential oil out of the rear end onto the brake shoes. you will have to pull the rear axle to replace the seal and clean the rear brakes/area with brake cleaner or replace the rear brakes if they are too soaked with brake fluid.

Ok...a leak in the front diff seal could not have been caused by an axle bearing/seal replacement. However, as I stated, the fluid level should have been checked after the job was completed. Further, front (called a pinion seal) leaks do not happen all of a sudden, rather they seep fluid for quite some time before failing. (unless the outer or inner pinion bearing has failed) THAT should have been easily noticed by the tech while he was working on it.
If the differential is noisy, I would not bother having the seal replaced as noise (usually howling or grinding) indicates a gear or internal bearing problem that is very expensive to repair. If you are at that point, best to obtain a used unit, end to end, (of the proper ratio) and replace it with that.
Depending upon what kind of flange or yoke you have on the diff, the seal is replaceable and inexpensive (less than $20). but you need some mechanical ability and proper instructions to do it.If done improperly, you will destroy the gears.

SOUND LIKE WORN DRIVE SHAFT BEARINGS AND A LEAKING DIFFERENTIAL PINION FLANGE SEAL.

i assume that you are talking about the seal at the front of the differential were the drive shaft bolts to the flange,if so this is called the front differential pinion seal,if your talking about the differential cover at the back of the differential(most rearward part of the rear end) this is called the differential cover gasket.

Could be low on differential fluid, leaking from the wheel seal. The Differential gears could also be worn from low on fluid or ears was not lined up and have worn it self out.

Service the rear end, inspect the fluid's condition and measure the any play in the gears in the rear end replace is worn out.

You may buy some time by running 50% to 100% Lucas oil treatment in your rear differential. Good luck and hope your differential is not to badly worn.

Section 05-02A: Axle, Integral Carrier — 8.8-Inch Ring Gear 1994 Town Car, Crown Victoria/Grand Marquis. Workshop Manual REMOVAL AND INSTALLATION Axle Shaft NOTE: Whenever replacing the rear axle lubricant, use Rear Axle Lubricant XY-90-QL (ESP-M2C154-A) or equivalent.
Removal
CAUTION: The rear brake anti-lock sensor must be removed before the axle shafts are removed. The rear brake anti-lock sensor is bolted on the rear disc brake caliper anchor plate.

1. Raise vehicle to desired working height. Refer to Section 00-02 . Remove rear wheel (1007) and tire assembly. Remove rear disc brake calipers (2552) and rear disc brake rotors (2C026) .
   
   
   
   
   

1. Clean all dirt from area of axle housing cover with a wire brush and/or cloth.

1. Drain rear axle lubricant by removing the axle housing cover .

1. Remove differential pinion shaft lock pin and differential pinion shaft .
   
   
   
   

1. Push flanged end of the axle shafts toward the center of the vehicle and remove the rear axle shaft retaining u-washer from the button end of the axle shaft .
   
   
   
   

1. Remove axle shaft from the rear axle housing , being careful not to damage the inner wheel bearing oil seal (1177) and rear brake anti-lock sensor ring.

Installation
NOTE: Check for presence of rear axle shaft o-ring (4A332) on the spline end of the shaft and install if not present.
CAUTION: Care must be taken not to let axle shaft splines damage oil seal or bearing assembly.

1. Carefully slide axle shaft into rear axle housing without damaging rear wheel bearing (1225) or rear brake anti-lock sensor indicator (2C189) . Start splines into side gear and push firmly until the button end of axle shaft can be seen in the differential case .

1. Install the rear axle shaft retaining u-washer on the button end of the axle shaft splines, then pull the shaft outboard until the shaft splines engage and the rear axle shaft retaining u-washer seats in the counterbore of the differential side gear .

1. Position the differential pinion shaft through the differential case and differential pinion gears , aligning the hole in the differential pinion shaft with the lock bolt hole. Apply Rear Axle Lubricant to differential pinion shaft lock pin . Install differential pinion shaft lock pin and tighten to 20-41 Nm (15-30 lb-ft). CAUTION: Differential pinion shaft lock pin must be tightened to specification using Stud and Bearing Mount E0AZ-19554-BA (WSK-M2G349-A1) or equivalent.
   
   
   
   
   NOTE: Axle housing cover must be installed within 15 minutes of application of the silicone rubber or new silicone rubber must be applied.
   CAUTION: Make sure machined surfaces on both axle housing cover and rear axle housing are clean before installing the new silicone sealant. Inside of axle must be covered when cleaning the machined surface to prevent axle contamination. Tighten the cover bolts in a crosswise pattern to ensure uniform draw on axle housing cover .
   

1. Apply Silicone Rubber D6AZ-19562-AA or BA (ESB-M4G92-A or ESE-M4G195-A) or equivalent. Install axle housing cover and tighten retaining bolts to 28-38 Nm (38-52 lb-ft).
   
   
   
   

1. Add Motorcraft Rear Axle Lubricant XY-90-QL or KL (ESP-M2C154-A) or equivalent until it is 6-14mm (1/4-9/16 inch) below bottom of fill hole. Add 118.3 mL (4 oz) of Ford Additive Friction Modifier C8AZ-19B546-A (EST-M2C118-A) or equivalent to Traction-Lok axles. Install fill plug and tighten to 20-41 Nm (15-30 lb-ft).

1. Install rear brake anti-lock sensor indicator . Tighten retaining bolt to 4.5-6.8 Nm (40-60 lb-in).

1. Install rear disc brake caliper and rear disc brake rotor .

1. Install wheels and tires.

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1. Insert Rear Bearing Remover T85L-1225-AH in bore and position it behind bearing so tangs on tool engage bearing outer race. Remove rear wheel bearing and inner wheel bearing oil seal as a unit, using Impact Slide Hammer T50T-100-A.
   
   Rear Disc Brake Caliper Anchor Plate
   
   
   
   
   

1. Lubricate the rear wheel bearing with Rear Axle Lubricant.
   
   
   
   

1. Install rear wheel bearing into the housing bore using Axle Tube Bearing Replacer T78P-1225-A.
   
   
   
   CAUTION: Installation of rear wheel bearing or inner wheel bearing oil seal assembly without proper tool may result in an early bearing or seal failure. If inner wheel bearing oil seal becomes cocked in bore during installation, remove it and install a new one.
   

1. Install the inner wheel bearing oil seal using Axle Tube Seal Replacer T78P-1177-A. Use Premium Long-Life Grease XG-1-C or K (ESA-M1C75-B) or equivalent between the lips of the inner wheel bearing oil seal .
   
   
   
   

1. Install axle shafts as outlined.

Wheel, brakes etc that are in way of pulling axle out have to come off. Drain rear end fluid, remove rear housing cover, remove bolt that holds pin in differential, remove differential pin, push in slightly on axle to remove "U" clip that holds shaft in, then slide shaft out. replace seal. Reverse procedure for re-install & fill with gear lube. If any questions, get back to us.

if it is the seal, you will have to remove the caliper and rotor, remove the differential cover and remove the bolt and pin inside the diff carrier housing. push in the axle and remove the axle clip and pull out the axle use a seal puller or prybar to remove seal reverse the steps to assemble