Gear Change from: 4.11 (Rear Gear) to: 4.56 in my GT350

Discussion in 'Shelby GT350 Mustang' started by JohnVallo, Jun 5, 2018.

  1. JohnVallo

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    #1 JohnVallo, Jun 5, 2018
    Last edited: Apr 29, 2020
    I was a little surprised that my first gear swap from 3.73 to 4.11 wasn’t a more noticeable change.

    To read about the 3.73 to 4.11 change
    SEE LINK: https://www.mustang6g.com/forums/showthread.php?t=96590

    I ended up driving 4,000 miles with the 4.11 (Including two 1300 mi trips). Gas mileage was really no different with the 4.11 than the 3.73 gears.
    That 38-point change to the 4.11 was not a significant change. Originally, I had considered a 4.30 gear ratio, but no-one produced one for the Super 8.8. When I learned that a 4.56 was available from Yukon Gear I decided to go for it. Another 45-points may give me the change, (or a little more), that I originally wanted.

    Just so we’re on the same ‘Terminology Page’, here is the proper terminology for the following rear-end parts.
    Carrier Unit - The inner differential component that the ring gear bolts to. This unit transfers power from the driveshaft/pinion gear to the axles. Carriers are available in various types that are used in different vehicle applications. Common types are open carrier, traction lock, limited slip, torsen, detroit locker, spool, etc.
    Housing/Gear Case - Cast iron (or optional aluminum) unit that houses all of the internal differential components such as the carrier and ring & pinion gears. When all of the internal differential components are installed into the case, the unit is sometimes referred to as a "third member". In the case of the ’15 up Mustang IRS rear, it is referred to as the ‘Pumpkin’, or Loaded Differential Housing.

    The Story:
    As with the 4.11 swap, I found another 2016 GT350 low mileage 3.73 take-out housing. I could have located other used Super 8.8 Mustang rear ends, but with the GT350 you know Exactly what you are getting: (A painted cast iron housing, a 3.73 gear ratio, a Torsen T2R differential, and a Manual Trans Pinion Flange.)
    I purchased a Yukon 4.56 Gear (pn: YG F8.8-456-15) from Summit Racing Equipment. They had a pretty good price of $233.00, Plus a $40.00 rebate. On the Install-Kit, this time I decided to buy the parts I needed individually, for 2 reasons: (1) Because upon teardown, this take-out rear end looked amazingly new. All the bearings & other parts looked great. (2) I still had pinion shims and a few other parts left from the previous Ford R&P Install Kit I had used before.
    I ended up buying: a Collapsible Spacer and Pinion Nut Kit (FORD pn: FL3W-4C121-BA), as well as a carrier bearing shim kit (RATECH pn: 1148), and a 2 qt. bottle of BG Ultra Guard LS Heavy Duty Synthetic Gear Oil 75w-140 (pn: 75364).
    To keep my original/spare housings safe and sound I decided to make a couple of nice wood fixtures to keep them stored in.
    Stow Cradle Final-1.jpg

    Upon receiving and examining the Yukon gear set I noticed that the machining (On the pinion bearing surfaces) had been done after the heat-treat as they looked newly machined. This was a definite indication that the process used to manufacture this gear set was the (FM) Face-Milled Process, -or sometimes referred to as the 5-cut process-. Different than the (FH) Face-Hobbed process, now used for virtually all newer Ford OEM production vehicles.
    When setting up the ring and pinion it is very important to know what manufacturing process was used to make your gear-set, because the 2 set-up procedures are different for each. Other ways to tell the difference is if your ring gear has a non machined casting area or bevel toward the backside, or looking at the teeth on the ring gear, you see that the teeth are equal height from heel-to-toe, you have a (FH) Face-Hobbed, gear-set. If the entire outside diameter and bevel of the ring gear looks machined, and looking at the teeth on the ring gear, you see that the teeth are taller at the outside diameter than they are on the inside diameter, you have a (FM) Face-Milled, or 5-cut gear set.

    For a complete understanding of the different manufacturing processes used,
    SEE: http://gearsolutions.com/features/face-off-face-hobbing-vs-face-milling/
    SEE: http://www.crownracegears.com/gear_cutting.html

    Also, upon measuring the pinion surfaces with a micrometer (Both the inner bearing surface and outer bearing surface), I discovered those surfaces were about 1 ½ thousands larger (OD) than the previous 4.11, and the original 3.73. This did require me to take some fine sandpaper and spend 45 minutes to get both OD’s down to ½ thousands within specs.
    Yukon Pinion Final.jpg

    One thing that I was concerned with was heat. Although I don’t track my Shelby, but I do some pretty spirited street driving and since I have a base GT350 I don’t have the Diff Temp gage and cooler. Knowing that the 4.11 was maybe going to run a little warmer, what I did on it was put an 8 TEMP THERMOLABEL 210-280F on the rear end in 2 places (Under the pinion on the cast iron surface, and on the back on the aluminum cover.) At least with this I could tell if the Temp ever got between 210 and 280 degrees) Which it Did Not in 4000 miles.
    Thermo Labels Final.jpg

    While doing this latest swap (4.11 --> 4.56), I learned that I could actually get the Diff Temp Dash Display Gage working and also enable the Trans Temp Gage on the dash display.
    Learning from the following thread, (These Guys are Truly Amazing !)
    SEE LINK: https://www.mustang6g.com/forums/showthread.php?t=69499&highlight=Diff+cooler

    For my Diff Temp Gage to work, I did the following:
    1. Run (2) 20ga. wires from the left-side drivers kick panel Connector C-264 -Tap into wires #4, and #21) run to behind the back-seat area and to the rear of the Diff. cover connected to a Motorcraft Pigtail (pn: WPT 984), and a Brass Temp Sensor (pn: FORD 9L8Z-6G004-E , or Standard Motor Products TS-653) is needed to screw into the rear of the Diff. cover. (The threaded recess for it is already there).
    I made a nice tape-wrapped wire harness and fished it thru the driver’s sill and rear seat left panel then down thru the body between the rear seat and trunk. (Right beside where the existing harness goes thru). A big Thank-You to @jwb for sending me the connector terminals.
    2. After the wiring was completed and sensor was plugged in I went into Forscan and enabled both the Axle Oil Temp and the Trans oil Temp for the Dash Gage Display. (In the IPC module: 720-06-01 xxxx Xxxx xxxx) Just change the location (where the large X is) to a 9.
    The Transmission already has a temp sensor, it’s Just not enabled in the Software for the Dash Gage Display.
    SEE LINK: https://www.mustang6g.com/forums/showthread.php?p=1985119&[email protected]#post1985119
    DashGageDisplay-Final.jpg

    UPDATE: To read about my own fabrication of a Finned Aluminum Rear Diff Cover that holds more fluid
    SEE LINK: https://www.mustang6g.com/forums/th...-for-the-mustang-‘super-8-8’-rear-end.117720/

    Concerning the Speedometer
    I have read repeatedly that if you make a minor change to your rear-gear (Within certain percentages) your speedometer will remain accurate. (Taking that to mean if you made major changes it would not).
    My speedometer remained accurate with the 4.11 gear, and also with the 4.56 gear, requiring NO changes.
    Well, here is what I conclude. FORD -using the magnetic triggers (located within rear knuckle inner bearing, or on some on the half-shafts) to drive the speedometer reading- the computer doesn’t really care what rear-end ratio it has, concerning the speedometer. It only has to know the tire circumference to get an accurate MPH. Because it is sensing the rear axle revolutions at the wheel, the rear-end ratio doesn’t come into play. Being there is a sensor on both sides, if one side turns repeatedly faster/slower than the other side, this will trigger the ABS system. (Now when they used to sensor at the back of the transmission, both the rear-gear ratio and the tire size would affect the speedometer.)
    I know the software has a location for the Rear Gear Ratio, (In the BCM Module: 726-12-01 XXXX xxxx xxxx (where XXXX is the Hex representation for your Ratio, Hence 0175 is hex for 373, 019B is hex for 411, and 01C8 is hex for 456. I did change mine, somewhat later after the gear swap, -but it did not seem to affect anything-.
    Here's some more logical explanation and info on the subject:
    https://www.mustang6g.com/forums/threads/speedometer-calibration.110607/page-2#post-2875272

    Now the part where I may have gone astray.
    While I had the rear end housing out I thought about doing 3 more things.
    1. Some stronger diff bolts -Lethal Performance (pn: LP-550179), and a 14mm HS drill bit -There were reported problems with the factory original bolts shearing, mostly on higher HP mods, and launches from dead stop) . These are the strongest bolts available.
    SEE: https://www.mustang6g.com/forums/showthread.php?t=74891&highlight=Extreme+diff+bolts
    2. Definitely needed a Steeda Cradle Alignment Kit (pn: 555 4438) to properly center and locate the Cradle back to the body squarely, (As I did drop the Subframe (Cradle) this time to drill out the front Diff bushing holes to 14mm)
    3. Possibly some BMR Red poly diff lock-out bushing inserts (pn: BK 051) to reduce diff to subframe movement.
    This obviously violated my #1 sworn policy: (NEVER CHANGE MORE THAN ONE THING AT A TIME)

    Anyway, this is what I did and I figured I could always remove the lock-out bushing inserts later if they caused too much NVH, which they Did!
    Concerning the BMR BK051 Diff Bushing lockout kit
    This kit consists of 4 polyurethane bushing inserts (And Hardware) that fit into the voids of the Differential-to-Cradle Rubber Bushings. I read/heard no real complaints or issues on installation from any regular Mustang, GT Mustang owners. On the GT350 one of the Diff Bushings is different. -The Left Side (Drivers) Rear bushing is slightly different, (The void space is slightly smaller (OD), and the Nub Pattern in the Bushing itself is different). This required modification to one of the Red Poly inserts.
    SEE LINK:
    https://www.mustang6g.com/forums/showthread.php?p=2212523#post2212523

    Again, the rear-end build went relatively well
    4.56 Ready For Assembly-Final.jpg
    Pattern Check Final.jpg

    TIP:
    A fact some may not know when setting the proper backlash, using the carrier shim packs.
    To aid in easier removing/installing of Diff assy, Use .003 thinner shim packs -On Both Sides-
    Then when ready for final assembly, add the .003 shims back to each side to give proper carrier bearing preload.
    After the proper backlash is achieved and the carrier shim stack thickness (on each side is known),
    (Sometimes the thinner shims get warped, beat-up and wrinkled from changing them several times.)
    I usually always order the solid carrier bearing shim (1 piece) from Ford Parts for Final assembly.
    Ford has them -in one solid piece-, from .242 thru .307, in 001 increments.
    Carrier Bearing Shims.jpg

    When installing the Steeda (Delrin) alignment bushings, I had read some people having trouble with having to pry excessively to align-up the holes in cradle bushings/delrin to the threaded holes in the body. I saw that some even had thread stripping problems. I studied my situation briefly and noticed by the bite-marks -that my original Cradle-to-body alignment had been centered pretty well. I also noticed that when I jacked up the cradle to start to align the holes, my cradle was ½ bolt hole to the rear of being centered and lined-up, so I had to pry it forward for the holes to align. It seemed the rear springs were keeping the cradle from going forward enough to line-up perfectly. I pried the cradle forward with a small bar in the original factory alignment holes/slots) and started the Left Side (Drivers) front bolt first. Then the Right Front. After drawing the front bolts up close, (but not tight), I was able to start both rears without any prying.
    After buttoning up everything and torqueing all the suspension bolts at ride height, I was ready for the road test.

    Here was a Big surprise
    I did run the drive-train (While still up on jack-stands) for about 5 minutes. Varying from First to Second at low RPM’s and even in Reverse for a couple of minutes. When the ABS lights all lit-up on the dash display, I thought it was time to stop.
    On the road test I was surprised, and not very happy. On every up-shift the drivetrain had this noticeable (loud) clunking, (Kind of a metallic clunk every time I up-shifted and sometimes just pushing in the clutch when moving). Also, slight noticeable gear whine, -coming in at 48 MPH and lasting to 52 MPH- Only on very Light acceleration and Float. I only drove about 7 miles and went back to re-check all the drivetrain and suspension bolts again. (All were good).
    Being very disappointed (After all, I had a pretty good pattern on the gear setup? What went wrong?)
    I thought about it that night and got up early the next day and took a longer ride, this time really checking for drive train slack at low speeds, different shifting scenarios, and really getting a feel for what might be going on. That time I noticed that on normal shifting, I would get a clunk during up-shifting as soon as I let out the clutch, and then immediately another clunk on acceleration. A DOUBLE CLUNK, -If you will-. (It was pretty loud on all up-shifts except 5th to 6th.)
    I wondered, could it be the Torsen?, did I need a better gear set-up?, why all the noticeable slack in the drivetrain?
    After everything cooled down again I decided to remove the driveshaft, lock down the axles with the emergency brake on, and put an angle-finder at the pinion yoke to measure exactly how much slack was in the rear-end. (5-6 degrees), That’s not real tight but it is not too uncommon for the New Mustang’s drivetrain.
    I then drove the car out to the interstate. This time I was moving a little faster. At (85MPH in 6th gear turning 3000 RPM), I noticed a slight ambient roar inside the cabin start to develop. (Sounded like it was coming from rear-end). Slowing down to 80 it went away. (Even more puzzling).
    Just then I realized what may be causing some of this. -I had violated my #1 policy-, (I had changed more than one thing at a time…) THE POLY LOCKOUT BUSHING INSERTS.
    Went back to the garage, again waiting till the next morning when everything was cooled off, I removed the 4 Poly Bushing inserts.

    Here was a Little surprise
    Again, a road test. 75 percent of the Rear-End whine (Especially at 48-52MPH) GONE.
    The Clunking, (or Double-Clunking) syndrome turned into a kind of Thumping, or Double Thump when up-shifting -Not as loud but still unacceptable (To me). Removing the Poly inserts definitely had a big effect on all the noises. If I were to continue with normal and occasional spirited street-driving, I wouldn’t be needing/wanting those in.

    Some insight on the clunking/thumping
    Some of this phenomenon I learned may be due to the design of the Dual-Mass Flywheel.
    There is actually up to 16 degrees of free-play in this (Dual-Mass Flywheel and Clutch unit)
    The clutch-discs and pressure-plate can actually have 16 degrees of: Free-Play. In other words the Clutch-Discs/Pressure-Plate moves but the Flywheel/Ring-Gear does not.
    Here is a page from the Ford Shop Manual describing the inspection/checking procedure for this Dual-Mass Flywheel
    Shop Manual Dual Mass Flywheel inspection.jpg

    Now for the Comparison/Evaluation of the ratios:
    This (.45) point change (From 4.11 to 4.56) was a little more than my first (.38) point change (From 3.73 to 4.11), For a total change of (.83) points. If you look at the chart below, it’s really only about 750 RPM difference from: 3.73 in 5th gear at 70 MPH, to: 4.56 in 5th gear at 70 MPH.
    Too much gear?, Most definitely NOT !
    Here is a chart of the comparison of all 3 gears, speeds, and approximate RPMs.

    3.73 Rear Gear
    Trans Gear/Speed(MPH)/Engine RPM
    5th / 50 / 2250
    5th / 60 / 2750
    5th / 70 / 3150
    5th / 80 / 3650
    6th / 50 / 1400
    6th / 60 / 1700
    6th / 70 / 2000
    6th / 80 / 2250

    4.11 Rear Gear
    Trans Gear/Speed(MPH)/Engine RPM
    5th / 50 / 2500
    5th / 60 / 3000
    5th / 70 / 3500
    5th / 80 / 4000
    6th / 50 / 1600
    6th / 60 / 1900
    6th / 70 / 2200
    6th / 80 / 2550

    4.56 Rear Gear
    Trans Gear/Speed(MPH)/Engine RPM
    1st / 10 / 1900
    1st / 20 / 3600
    1st / 30 / 5400
    2nd / 20 / 2500
    2nd / 30 / 3600
    2nd / 40 / 5000
    3rd / 30 / 2700
    3rd / 40 / 3550
    3rd / 50 / 4450
    4th / 40 / 2750
    4th / 50 / 3450
    4th / 60 / 4200
    5th / 50 / 2800
    5th / 60 / 3300
    5th / 70 / 3900
    5th / 80 / 4400
    6th / 50 / 1750
    6th / 60 / 2100
    6th / 70 / 2500
    6th / 80 / 2800

    What to do now
    After only 150 miles on this Rear Gear, I decided it was time to remove this Clunky-Assed setup.
    I ended up putting the Original 3.73 back in. (Mainly for the following reason).
    -I wanted to perform the slack test with the angle finder on the original rear end, so I would at least have a comparison on the amount of driveline slack difference between the two rear ends. The original 3.73, Torsen had exactly 5 degrees of driveline slack, measured at the pinion yoke, with the emergency brake on. And as referenced earlier, the 4.56 setup had 6 degrees.
    So my plan now is to tear down the 4.56 and look closely at the Torsen, possible try some different pinion depths/backlash and look at the pattern again. Need to eliminate the whine and try to correct the thumping noise on shifting.
    With the original 3.73 gears back in, the cars shifting (especially upshifts) is much smoother, (Definitely less jerky), than the other 2.
    With the 4.11 gear I did notice I needed to use my (Rev Matching skills) somewhat to obtain the same smooth shifting. (Even on Upshifts)
    With the 4.56 Even my Rev matching skills couldn’t produce perfectly smooth shifting.
     
  2. Trackaholic

    Trackaholic Well-Known Member

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    Great read! If you have any photos of the work, please post some.

    -T
     
  3. Mjc1241

    Mjc1241 Well-Known Member

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    Great write up John.
     
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  4. TxOilMoney

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    WOW. John, you have posted one of those rare masterpieces this forum has produced over the last 2 1/2 years. In depth, precise, well thought out, and very well outlined. Mine is a 2016 Tech Pack, so this pertains directly to me, since I actually track my car. I'm one of the very few to NOT have experienced limp mode. True, three track events doesn't prove shit and I'm not stupid enough to think I'm immune. My on dash Trans Temp gauge has hit 280, but stopped just shy of the limp boundary, which we think is around 290 or 300. I've used BG hi performance gear oil in the tranny and diff since the git-go. Maybe that has helped.


    Based on the information in your post, I have renewed confidence and a real plan to solve my future track issues all at once. Cooling, gearing, and I just ordered the Vorshlag bits. All I need now are some R wheels and tires.


    Thanks for taking the time to write this up.
     
  5. Tomster

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    Amazing work!
     
  6. Hack

    Hack Well-Known Member

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    Great write up, but IMO the main reason for installing deeper rear gears is to improve launching the car from a stop. You didn't say whether you felt it was improved and nothing about how the car worked in first or second gear with the differential change. Do you have any feedback about this?
     
  7. MAV

    MAV Well-Known Member

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    My #1 wanted mod for this car even before I got mine was 4.56 gears. Glad to know the gears are now available, and I will likely be installing them soon. Anxious to hear your thoughts on the changes in drive characteristics with these gears...
     
  8. OP
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    JohnVallo

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    #8 JohnVallo, Jun 7, 2018
    Last edited: Oct 28, 2018
    Regarding the characteristics in the lower gears and the launching from a stop, there were a couple of things I did notice. The car positively felt more responsive in first and second. Was easier to spin the tires. I’m more of a ‘Hammer Down’ -from a rolling start- type person, so I didn’t get to do too much of the dead stop launches. The Yukon Kit Installation Instructions specifically warned against any heavy acceleration for the first 100 miles. One thing I bet will happen, when the GT500 comes out we will get a lot more feedback concerning the launching from a stop.
    In normal driving I did notice easier starts from a stop, what I mean by that is the less likelihood of stalling from a rapid release of the clutch from a stop. I know when I first got this car the clutch pedal was so soft and easy to release, I did stall the car a couple of times till I got used to its feel. The Steeda clutch spring mod helped this condition and is highly recommended.
    For those who track their GT350, I certainly would not be concerned with moving toward a steeper gear. On some of the shorter track layouts I would probably be wanting a 4.88 in this car, and really, it still would not be too much for the street.
     
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  9. rocket71

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    Can you advise where you are sourcing the rearends? I am in need of one for a simliar gear change.
     
  10. 50 Deep

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    Way to geek out on the details brother! Excellent read
     
  11. Brazos609

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    It doesn't look like you needed a case spreader for either swap. Did the carriers come out easily without a lot of prying?
     
  12. OP
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    #12 JohnVallo, Nov 7, 2018
    Last edited: Dec 2, 2018
    According to the Ford Shop Manual they use a slightly different method of spreading this case, than what I've seen in the past.
    I used 2 large pry bars. Prying one from top and one from bottom against the heads of the ring gear bolts, carrier came out fairly easy.
    When setting backlash I use a shim pack .003 thinner on each side, so carrier can be removed real easy. Then on final assembly I add the .003 back to each side.
    PryBar-Final-1.jpg
     
  13. sublime1996525

    sublime1996525 Well-Known Member

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    Awesome! I’m curious to hear more if you decide to put the 4.56’s back in. I would’ve thought you’d lose a lot more RPM.
     
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    #14 JohnVallo, Dec 1, 2018
    Last edited: May 25, 2019
    The 4.56 gears are back in, whine is gone, all is well, and awesome acceleration to 120+
    Here’s the story:
    Finally got around to tearing down the 4.56 carrier for close inspection. My primary concern was the slight gear whine at 48-52 MPH on float & light acceleration.
    Also, I checked the Torsen assy. very closely, and found No problem with it. The special ‘Peregrine’ Torsen unit for the GT350, basically has 24 parts, and is built to last a lifetime as there are no service parts available for it.
    I have had several of these apart and never found any issues, They always look like new.
    Anyone who was wondering what was inside the T2R Torsen, or who had never seen one, Here you go:
    Torsen Dissembled.jpg

    After re-reading the Yukon Ring & Pinion installation instructions one thing stood out to me that I had not caught before. (By the way, this is the first Yukon Ring & Pinion that I have used). In the past I had always tried to get the best compromise on the gear contact pattern as I could, attempting to center the pattern both from Heel-to-Toe, as well as from Top-to-Root. The Yukon instructions emphasize the Top-to-Root pattern should be the primary concern, and not worry about where the Heel-to-Toe pattern lies. After rolling another contact pattern with yellow marking compound and looking at my pattern again, (Which I thought was pretty good), I realized that the Top-to-Root was just a little deep (Requiring a thinner pinion shim). I had a .040 pinion shim already in it, so I reduced the shim to .035. This centered the Top-to-Root pattern perfectly, but made the Heel-to-Toe pattern just a little higher (Towards the Heel).

    Before Gear Pattern:
    Old Pattern Check Final.jpg

    After Shim Change Gear Pattern:
    New Pattern Check Final.jpg


    I played with the backlash a couple of times also and ended up with a perfect .008 backlash.
    Dial Indicator Setting Backlash.jpg

    A little about the Collapsible Spacer (Crush Sleeve)
    The best Crush Sleeve is -NO Crush Sleeve: (i.e. Solid Spacer), I guess the reason they use a Crush Sleeve is to save assembly time, and cost. You can complete the final assembly the first time. With a solid Spacer w/Shims, its more expensive to manufacture, and it usually takes a couple of dis-assemblies to get the correct preload.
    I usually always buy 3 crush sleeves from Ford when I buy parts. On this job, I crushed the first one a tad too much (40 in. lbs. of Pinion Preload), -Too much-. The second crush sleeve was put in and Wow, (I think I put at least 600-700 Lbs. of torque on this bad boy). -Would NOT collapse-. I ended up breaking a 24” breaker bar. After replacing the breaker bar, I tried again, this time the breaker bar and a 36” jack handle extension was-a-bowing, and the 1 1/8 deep socket broke.


    So, it was time for the third crush sleeve, which collapsed, and I got a perfect 10 ½ in. lbs. of Pinion Preload.
    Pinion Preload Final.jpg

    TIP: In an emergency you can renew a used crush sleeve, Here’s the best way:
    Get a piece of metal pipe, or in my case I used an impact socket.
    This pipe or socket should slide through the crush sleeve with a fairly tight fit.
    Then, with a large hammer, strike the crush sleeve, several times evenly all around directly on its bulge area. The pipe/socket should keep the crush sleeve from becoming oblong. This should make the crush sleeve slightly longer again which then may be reused. If you have a new one to compare it to, you'll know when it's long enough.
    Refreshing Crush Sleeve Final.jpg

    I think I've seen & heard all the used Crush Sleeve secrets, like using shims with the old one, or under torqueing the used one so it don't crush any more. Bottom line is: It's best just to use a new one.

    Crush Sleeve Final.jpg


    Now it was time to R & R (Remove and Replace), the carrier assy. I’m getting good at this.
    Decided to make a wooden cradle to remove the exhaust system.
    Wooden Exhaust Cradle Final.jpg

    Also made a Carrier Cradle to help with the Carrier R & R.
    Wooden Carrier Cradle Final.jpg

    When removing the rear knuckles, place the brake cables, Speed Sensor, and brake caliper safely out of the way.
    Caliper Out Of The Way.jpg

    TIP:
    I always like to align (Clock) the driveshaft back in the same relationship with the Pinion Yoke on reassembly. When reusing the same pinion yoke you should always mark both with an alignment line before disassembly. What I do (Mainly because I am installing a different Carrier/Pinion, I use Number stamps to mark all 6 threaded holes on the pinion yoke, and one mark on the driveshaft. In case I do end up having any vibrations, I will know exactly what position the driveshaft is in when I have to re-clock it to the pinion in a different position.
    Pinion Clocking Marks Final.jpg

    After driving a couple thousand miles, with the 4.56, I realize this gear ratio is really Not at all too much for street/highway use. I really like it.

    Concerning Temperatures and Fuel Mileage...
    I drove quite a bit in the 93+ degree Florida weather, with the Blacktop being well over 120, The highest I saw the Rear Axle Temp was 238.
    In 80 degree weather, it usually stays a little over 200 when fully warmed up.
    The Transmission temps usually always run about 10 to 15 degrees warmer than the Rear Axle.

    UPDATE: To read about my own fabrication of a Finned Aluminum Rear Diff Cover that holds more fluid
    SEE LINK: https://www.mustang6g.com/forums/th...-for-the-mustang-‘super-8-8’-rear-end.117720/

    Trip Gage Final-2.jpg

    Gear Ratio, MPH, RPM Chart-1.jpg

    Stay tuned for more... I just bought a 4.88 R&P, and another GT350 Complete Housing Take-out.
    IMG_0173-a.jpg
     
  15. blueghost

    blueghost Active Member

    First Name:
    Bode
    Vehicle(s):
    2018 GT350, 1967 GT350, 1961 Ford Starliner (HM 427)
    Joined:
    Jun 13, 2018
    Location:
    West Texas
    Posts:
    25
    Likes Received:
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    0   0   0
    John,

    Thanks for the 8.8 gear info. Being a 9 inch guy I feel your pain with the gear whine.

    Since I'm a top-end guy I'm going the other way with my gearing, most likely to a 3.55. I'm just going to keep taking gear out of it until I can't hit the limiter in 5th. :)

    Grace and Peace,
     
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