trusktr
Active Member
- Joined
- Dec 17, 2018
- Threads
- 9
- Messages
- 32
- Reaction score
- 4
- Location
- Oakland, CA
- First Name
- Joe
- Vehicle(s)
- 2017 Shelby GT350
Hello! Did you do the 4.88 gear change yet? I didn't see a post. How'd that go?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:
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:
After Shim Change Gear Pattern:
I played with the backlash a couple of times also and ended up with a perfect .008 backlash.
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 a couple of crush sleeves from Ford when I buy parts. On this job, I collapsed 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.
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.
I think I've seen & heard all the used Crush Sleeve secrets around, 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.
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.
Also made a Carrier Cradle to help with the Carrier R & R.
When removing the rear knuckles, place the brake cables, Speed Sensor, and brake caliper safely out of the way.
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.
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/
View attachment 323407 Stay tuned for more... I just bought a 4.88 R&P, and another GT350 Complete Housing Take-out.
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