Gear Replacement How To, Like it?

R.J.

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Aug 20, 2003
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Warwick, Rhode Island
8.8 Inch Gear Replacement

Disassembly

1. Remove the rear wheels

2. Remove the brake calipers with a 13mm wrench.

3. Remove the caliper brackets with a 15mm wrench. Then remove the rotors.

4. Mark the driveshaft flange and the pinion flange so you can assemble it the same way. Remove the driveshaft from the pinion flange with a 12 point 12mm wrench. Slide the drive shaft out of the Tranni and remove it from the car.

5. Disconnect the rear sway bar from both lower control arms (13mm). Remove the sway bar from the car.

6. Remove both rear ABS sensors from the brake mounting plate. (Inverted Torx T-8)

At this point it is optional to remove the differential from the car. It will make the measuring processes easier.

Differential Removal

1. Disconnect both Quad Shocks at the differential.

2. Loosen attachment hardware and remove just the nuts at the following points: both shocks lower attachment points, both upper and lower control arm attachment points at the differential. (18 & 20 mm)

3. Place a jack under the a lower control arm. Remove the lower control arm to differential bolt Slowly lower the jack and as the control arm comes down the coil spring will come loose and can be removed form the car. Repeat on the other lower control arm and spring.

4. Place the jack under the center of the differential to support its weight.

5. Remove both shocks lower bolts.

6. Remove both upper control arm bolts at the differential.

7. Balance the differential on the jack and lower it out of the car.


Now the differential is either out of the car or still in the car but its ready for the ring and pinion to be removed.

1. Place an oil drain pan underneath the differential housing.

2. Remove the rear cover of the differential. (13mm) Drain all of the fluid from the housing.

3. Rotate the differential until you see the differential shaft locking bolt. Use an 8mm combination wrench to remove this. For some extra leverage you have two options: first you can put an 8mm wrench on the bolt and turn one of the axles until the wrench hit’s the housing and pushes on the wrench in a loosing direction. Continue to turn the axle and your increased mechanical advantage will push on the wrench hard enough to turn the bolt. OR Have an assistant hold a pry bar in the wheel studs of one axle, so when you pull on the wrench the carrier does not rotate.

4. Rotate the carrier until one end of the differential shaft (c-clip pin) is visible. Reach around the carrier and push the other side of the shaft so that it hangs out of the carrier on the visible side. Pull the shaft out of the carrier.

5. Push the axles inward, toward the differential. This will expose the C-clips, which retain the axles in the housing. Remove both of these clips with a screwdriver and magnet.

6. Now you can remove both axles.

7. Use an axle as a seal removal tool and pry both axle seals out of the end of the axle tubes.

8. Using a slide hammer and the appropriate attachment pull the axle bearings out of the axle tubes. If your seals were seized into the axle tube when you tried to pry them out, then they will come now, with the bearing, when hit by the slide hammer.

9. Mark the main bearing caps left and right, I simply put them on one side of the floor. Left goes on left of car, right on right. (arrows facing out) Remove the four bolts from bearing caps and remove the caps.

10. Using a pry bar to brace the differential, turn the pinion flange. The ring gear will ride up on the pinion gear and pop loose. Remove the differential from the housing. When the differential is removed be sure to catch the side shims and note which side they are on.

11. Using a 1-1/16” socket remove the pinion nut.


12. Using a three jaw puller, remove the pinion flange from the pinion gear. Now tap the pinion gear out of the housing with a rubber mallet.

13. Using a seal puller, remove the pinion seal. Under the seal will be an oil slinger (looks like a shim or big flat washer). Remove the slinger and the pinion bearing.

14. With a steel punch, punch out both pinion-bearing races and then drive in new races.

15. The last step is to spray down the inside of the housing with some good brake cleaner.

There are two recommended methods for calculation pinion shim thickness. I prefer using a Pinion depth tool. This first method will be the less preferred method.


Calculating Pinion Shim Thickness With a Pinion Depth Tool

1. Install a sanded down pinion bearing onto the pinion with NO shims. This bearing should have its inner diameter sanded down until it slides on and off the pinion easily.

2. Install the pinion gear and bearing into its bore.

ZERO YOUR PINION DEPTH TOOL
1. Install the required extension (2 or 3 inch) into the dial indicator.
2. Install the dial indicator into the nut and collet.
3. Slide the indicator tip with extension into the matching (2 or 3 in) calibration tube. Hold the calibration tube flush against the bottom of the tool.
4. Move the dial indicator down through the collet and into the calibration tube until the indicator bottoms out and the needle moves about .030. (This is to insure that the extension is 2+ inches into the tube)
5. Tighten the collet, making sure that the tube stays flush against the tool.
6. With the collet tight and the extension bottomed in the tube, you can now set the dial indicator to zero.

3. Find the diameter of the differential side bearing race (dial calipers are great for this). Ours measured 3.063 inches. Divide this number in half.
3.063" ÷ 2 = 1.531"

4. Measure the distance between the main bearing cap mounting surface and bearing bore. Since we are working with a 1.531 inch bearing race diameter, we used a two inch extension on the pinion setting tool to get a complete reading. Our indicator read .465 inch.

5. Subtract the bearing bore reading from the length
of the pinion tool extension. This is the actual axle centerline.
2.000" – .465" = 1.535"

6. Subtract the bearing race diameter (divided by 2), in step 3, from the axle centerline in step 4. This is the amount the axle housing is off-center. Our axle was off-center by .004 inch.
1.535" – 1.531" = .004"
-If your bearing bore measurement is less than the race diameter (divide by 2) then you will be adding the offset to the total pinion depth in step 8.
-If your bearing bore measurement is greater than the race diameter (divide by 2) then you will be subtracting the offset from the total pinion depth in step 8.

7. Now you need to measure the distance from the bearing cap mounting surface to the face of the pinion gear. Since the pinion depth marked on our pinion gear is 2.552 inches, we used a three inch extension on the pinion setting tool. Take a couple of measurements, rotating the pinion and leaving the tool in one spot. (outer edge near the teeth). Your readings should be consistent. In our case, the measurement was .416 inch.

8. Subtract the reading from Step seven from the length of the pinion tool extension, as shown in our example:
3.000" – .416" = 2.584"

9. Next, subtract the off-center figure from Step six from your answer in step 8. This will give you the actual pinion depth:
2.584" – .004" = 2.580"

10. To find out how much you need to shim the pinion gear, subtract the depth marked on the pinion gear head from the actual pinion depth you just found in step 9:
2.580" – 2.552" = .028"
Thus, we need a .028 inch pinion shim pack.
**IF you are installing a gear set with out a pinion depth marked on the pinion head then there is a little more math involved. To figure out the number to subtract from the pinion depth in step 10 you will need to do the following:
1. Measure the thickness of the new pinion head (from bearing flat to gear head)
Ex. 1.888
2. Subtract this measurement from Fords OEM Factory mounting distance for the 8.8 in rear end: 4.420 (this number is a constant)
4.420 - 1.888 = 2.532

Summary

(2.00(extension) - bearing bore measurement) - (bearing race diameter / 2) =
Off set

3.00(extension) - Distance to Pinion head = Pinion depth

Pinion depth + or - Off set = Actual Pinion depth

Actual pinion depth - Number on pinion head = Pinion shim required.

Example

(2.00 - .465) - (3.063/2) is 1.535 - 1.531 = .004

3.00 - .416 = 2.584

2.584 - .004 = 2.580

2.580 - 2.552 (a number on a pinion head) = .028 shim required

Pinion Gear Installation

1. The first thing we will do is install the pinion shim (the size in which we just figured out) and pinion bearing onto the pinion. Either press it on or boil the bearing for 10 minutes and it will slide right on.

3. Install crush collar onto pinion gear. You have two options for crush collars:
-First is the OEM style that actually crushes and as you crush it your pinion rotation force increases. Use of this style is explained in step 5.
-Second you have a Solid Pinion Spacer. It is a solid metal ring (does not crush) and a stack of shims. The installation of this optional piece is also explained in step 5.

4. Install pinion gear in housing and install flange and pinion nut loosely.

5. This is where you will need a beam type inch/pound torque wrench (1in lb increments) for both collar type installations. Also a long breaker bar for the crush collar or a 125 ft-lb torque wrench for the solid spacer.

-CRUSH COLLAR: Tighten the pinion nut down until you can no longer move the pinion gear back and forth. When moving it, you will hear a clicking noise from the play, tighten until the noise stops. Using your inch/pound torque wrench to check for pre-load (force it takes to continually rotate the pinion), tighten the nut down until you have a drag on the pinion and it reads 16-29 in-lbs for new bearings or 8-14 in-lbs for used bearings. Be careful, once the collar starts to crush and you get a reading on the wrench, it will take VERY LITTLE to get it in the right range. Too much and you will exceed the limit. If you exceed the limit, you MUST install a new crush collar and start again. I suggest tightening in 1/16 of a turn intervals between checking. So you should tighten with a breaker bar, check pre-load with torque wrench, tighten with breaker bar, etc.

-SOLID PINION SPACER: To use a solid pinion spacer you must first measure the thickness of your old crushed collar. This measurement will tell you how much space your old collar was taking up on the pinion. Now measure your solid pinion spacer ring with none of the supplied shims. Add the correct shims to the solid ring to get as close as you can to the measurement of the old crushed collar. Install the solid ring on the pinion first then put the shims on top and install the pinion into the housing. Install the pinion flange and nut then torque to 125 ft-lbs. Check the pre-load (force it takes to continually rotate the pinion) to be in the above listed ranges. If you are to high you will need to switch to a larger shim and if you are to low you will need to switch to a smaller shim. The kit does not come with to many options so you will narrow down your best choice quickly. You get a .010, .012, .013, .015 and a .020 shim to work with.


Ring gear and carrier installation

1. Install the carrier side bearings by either pressing them on or boiling them for 10 minutes and they will slide right on.

1. Using some 300 grit or so sandpaper, sand down both the back of the ring gear, and the mounting surface of the differential it sits on. This will remove any high spots, which could throw off run-out and cause whining.

2. Heat up the ring gear with the boiling water. Line up the bolt holes and slide the gear as far down as it will go. Install 5 bolts in a star pattern. Tighten them down in a star pattern like you do for installing a tire. Do this evenly until the ring gear is fully seated. Remove the 5 bolts and put loc-tite on the bolts and re-install. Torque ring gear bolts to 70-85 foot pounds in stages.

3. Hold the races onto the bearings and put and put the carrier in the housing. Now slide the carrier to one side and install one of the old shims in its original place. Then move the carrier over toward that shim and install the other shim on the other side. It should be a little tight, where you would need a rubber mallet to tap them in.

4. Install main bearing caps and torque to 70-85 lb-ft.

5. Setup dial indicator to measure backlash (stick a magnetic base to the cover mating surface). The backlash should be .008-.015, I recommend shooting for .010-.011.

6. If you have too much lash, you need to move the ring gear closer to the pinion gear. This is accomplished by adding then subtracting an equal amount of shims from both sides. Whatever you take from the right, you install onto the left. If you have too little lash, the opposite is true, you need to move the ring gear away from the pinion gear. Again with equal and opposite adjustments. Do this until you get the backlash within spec.

7. Now setup the dial indicator to check the run-out of the ring gear. You want to setup the dial indicator to read the back of the ring gear, the part that sits on the differential. You should have no more than .004” of run-out.

Reassembly

If you have checked everything twice and all your measurements are in spec, you are finished with the gears. Now re-install the axles, c-clips, pin and bolt, brakes, diff cover, ABS sensors, driveshaft, and wheels. Fill the housing with gear oil and your new set of gears will serve you well. I have just a few finishing notes I will give you now.

1. Use loc-tite on the pin-retaining bolt.

2. Use loc-tite on the ABS sensor bolts and anti seize on the sensor where it touches the brake plate.

3. Instead of using a gasket on the diff cover, use RTV gasket maker. Its easier and works much better. Be sure to clean the area with acetone to get a good seal.

4. Gear break-in procedure should be as follows for a streetcar. Drive at normal street speeds for 10 miles; let it cool for 30 minutes. Do this 3 times and then let the car sit overnight. Check for whining or vibrations while doing this. Then the hard part: DO NOT drive the car hard for about 200 miles.

Torque Specs SAE
Pinion Bearing Pre-load, used 8-14 in/lbs.
Pinion Bearing Pre-load, new 16-29 in/lbs.
Ring gear bolts 70-85 ft/lbs. (in stages)
Main bearing bolts 70-85 ft/lbs.
Pinion shaft lock bolt 15-30 ft/lbs.
Driveshaft bolts 80-90 ft/lbs.
Gear Setup
Backlash .008-.015 “
 
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Jagerbeast

New Member
Mar 7, 2010
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Virginia
Nice write up!

I had to get my clutch plates replaced today, apparently only 1 of my wheels was spinning :mad:

Talk about a pain in the ass.
 

trombonedemon

Well-Known Member
Jun 25, 2009
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U.S.A, U.S.A., U.S.A.!
Nice write up!

I had to get my clutch plates replaced today, apparently only 1 of my wheels was spinning :mad:

Talk about a pain in the ass.

How is one of your wheels spinning? Our cars have Limited slip, one wheel should spin if you are cornering.:shrug: Is this a constant thing while going in a straight line or around a corner?
 

R.J.

Member
Aug 20, 2003
813
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41
Warwick, Rhode Island
Trombonedemon: Most of the time one wheel spin refers to a burnout, when both should be spinning. Also during cornering the limited slip allows one wheel to spin slower but they both spin.
 

Jagerbeast

New Member
Mar 7, 2010
516
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0
Virginia
Yeah ... My mechanic was saying that the clutch plates burned out because of 1 wheel spin "burnouts" like if your burning out while turning such as doing donuts or even just around a corner, It's putting more weight on 1 of the rear wheels. Another example he gave was if the car was stuck in the snow, and only 1 of the rear wheels was spinning. Needless to say, i was getting a metal on metal noise from my driver side rear wheel, which turned out to be the break rotor hitting something, mainly on left turns, because my axle was sliding in and out. While the car was up in the air, the driver side rear wheel was way easier to turn than the other side.

Thanks again for the write up, ill probly need it in the near future :nice:
 

R.J.

Member
Aug 20, 2003
813
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Warwick, Rhode Island
There is another GOOD method for figuring out pinion shims and it is called the Master Housing Dimension. I found a write up on how to do it but it does not make sense to me? The only part that I don't understand is where the 4.415 measurement comes from. If this number is supposed to be Ford's 8.8in factor measurement then I thought it was supposed to be 4.4199-4.420?!?!? If that is what this write up was going for and 4.420 is substituted into the equations then this is a great and easy (NO pinion depth tool required) method aslo.

The Master Housing Dimension (MHD) is the distance between the axle centerline and the back of the pinion head. This equals Pinion Head Thickness + Pinion Depth. Since your factory gears were installed using the MHD method from the factory, you know that your pinion depth was properly setup with the correct pinion shim. Since we are changing the pinion, we must now calculate the correct pinion shim thickness. For an example, if Pinion Head Thickness was 1.781 and the shim was .019” thick, doing the math: (4.415-1.781=pinion depth of 2.634) The .019” shim was used to reach that pinion depth of 2.634. If our new pinion head is now 1.770” thick, doing the math: (4.415-1.770=2.645 pinion depth). Since the difference in pinion thickness is .011 less on the new gear, we must ADD .011 to the existing .019 shim to get the correct pinion depth. This leaves us with a .030 shim for the new thinner pinion gear. If the new gear was 1.792, .011” thicker than the old gear, we would subtract .011 from .019 and use a .008” thick pinion shim. Using this method, I have double checked the MHD with my pinion depth checker and found it within .001” of my calculations on both installs. This is the easiest way to do it, and will save a lot of time in installing, measuring, disassembling, and changing shims; not to mention re-installing and measuring all over again.