Drivetrain '87 5.0 Installing New Ring Gear and Pinion - Pattern Questions

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karhoot

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Apr 23, 2026

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Apr 23, 2026

#1

• Apr 23, 2026

• #1

Hey all! First post. In the middle of a fox rebuild. Since I was working on jackstands, decided to pull the rear end & install gears in my garage versus on my back because it was simply easier. Set up pinion with original shim & set at a starting point of 16 in/lbs. This is what I got for a gear pattern. First time doing gears so looking for any insight on deciphering this!

 

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K

karhoot

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Apr 23, 2026

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Apr 23, 2026

#2

• Apr 23, 2026

• #2

karhoot said:

Hey all! First post. In the middle of a fox rebuild. Since I was working on jackstands, decided to pull the rear end & install gears in my garage versus on my back because it was simply easier. Set up pinion with original shim & set at a starting point of 16 in/lbs. This is what I got for a gear pattern. First time doing gears so looking for any insight on deciphering this!

Click to expand...

Just to add. Backlash is currently set at 0.010"

 

K

karhoot

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Apr 23, 2026

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Apr 23, 2026

#3

• Apr 23, 2026

• #3

Update: tested backlash at 0.012" and this was my new pattern. Just for reference

 

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AeroCoupe

lube between the nut and the face. I know my lubes

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#4

• Apr 24, 2026

• #4

Hope you do not mind but I changed the title of your thread as the other one wasn't as descriptive. Hopefully this will get the right two or three guys in here to help out.

@TOOLOW91
@rednotch
@General karthief

 

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Noobz347

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#5

• Apr 24, 2026

• #5

Nine Finger Wrenching just went through this on his channel too.

 

K

karhoot

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Apr 24, 2026

#6

• Apr 24, 2026

• #6

Noobz347 said:

Nine Finger Wrenching just went through this on his channel too.

Click to expand...

His issue was a bit different. He used wrong bearings and got an entirely different contact pattern due to that.

 

K

karhoot

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Apr 23, 2026

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Apr 25, 2026

#7

• Apr 25, 2026

• #7

Yet another update:
Did some more playing around with shims this morning. Adjusted pinion shim to 0.018" (from 0.016"). Had to change inner bearing & race as well.
Currently set up at 0.011" backlash with this pattern. Safe to assume I'm good now. Loosening backlash and thickening pinion seem to help that pattern pretty dramatically. It's the exact same pattern on 3 seperate points on the ring gear also.

 

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AeroCoupe

lube between the nut and the face. I know my lubes

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Apr 25, 2026

#8

• Apr 25, 2026

• #8

This video is pretty basic but I like how Eric covers the terminology so setting gears up makes a little more sense:

View: https://youtu.be/0Y6vOwiCe1U?si=Jy0eisu4F7aqsD_a


Part 1 on setting the rear end up:

View: https://youtu.be/5fARhE7v5Bg?si=f-eyWPyyE-Se9_r1


Part 2 on setting the rear end up:

View: https://youtu.be/npUBF9Wj1Iw?si=jny3bIVsBx5xyaVA


I have also attached FRPP .pdf of how to set gears up. I shows the patterns which is really helpful.

 

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General karthief

wonder how much it would cost to ship you a pair

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#9

• Apr 25, 2026

• #9

Ah....I paid a guy to do my....ahem, rear gears.

Hell, looks good from my house
Yeah, I know I'm useless......

 

K

karhoot

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Apr 28, 2026

#10

• Apr 28, 2026

• #10

Yet another update:
Proper break in, done.
Drove the car officially today & she's a ripper. 3.73 gears absolutely woke this thing up entirely

 

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Mindseye007

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#11

• May 9, 2026

• #11

karhoot said:

Yet another update:
Proper break in, done.
Drove the car officially today & she's a ripper. 3.73 gears absolutely woke this thing up entirely

Click to expand...

I love my 4:10's with my z-spec T5 2.95 1st gear is so sweet.