8.8 gear setup

thecj3man

Well-Known Member
Joined
Apr 8, 2005
Location
Fall Branch, TN
I am trying to install a 3.90:1 ring and pinion into an 8.8 explorer axle. I have played around with pinion depth trying to get a good pattern. My initial setup seemed to be very shallow. Pretty sure I fat fingered the calculator when I was figuring out my first try. I then went back to original thickness shim and it was better, so I thought I was going the right way. I have set it up 4 times now but I am not sure, so I thought I would ask opinions. Pinion depth is about 0.004 deeper into the pinion than what is written on the pinion and backlash is 11.5 which is just inside the 8-12 range that US gear recommended in the instructions
F64ADF59-1AF3-4FA0-91E0-7495D857FE30.jpeg

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Pinion definitely too deep. Pull out 10 thou and see what you got.
 
Deep. The hard crisp line in the grease and the pointing top gives it away.
Randy...wait. Treadway says it'll point the way it needs to go.
 
Thank you for all the replies. I currently have it shimmed .029, the factory shim was 0.019. I am going to go back towards 0.019 when I get home from work and see where it ends up.
 
I set it up at .024 earlier and it looked pretty much the same. I am going to check everything again and see what happens.

My biggest hangup is the checking distance that is written on the pinion. It seems the few gears I have installed aren’t within the plus/minus 0.003 of checking distance that the instructions call out when you finally get a good pattern.
 
thecj3man said:
I set it up at .024 earlier and it looked pretty much the same. I am going to check everything again and see what happens.

My biggest hangup is the checking distance that is written on the pinion. It seems the few gears I have installed aren’t within the plus/minus 0.003 of checking distance that the instructions call out when you finally get a good pattern.
Click to expand...
Then something isn't seated. A 5 thou change on a pattern like that one should be very noticeable. What I mean is even though it is obviously too deep, it isn't grossly deep. 5 thou either way will make a real definitive difference. As far as numbers etched on any gear go, I have found that isn't the most efficient way to determine depth. An OEM shim to start with and then making adjustments based off the pattern is best.
This is not the case when you have Spicer gears replacing Spicer gears and you can make adjustments based off the pinion variance numbers (assuming the OEM depth was correct).
All of that just say, take out some shims (make sure your races and inner bearing are seated) and recheck.
 
I rechecked all the races and bearings and they were bottomed out. Here it is at 0.019 pinion depth and 0.010 backlash. I also reset it at 0.024 pinion depth and 0.010 backlash, I will post them in a separate post.
8377CE0C-B8AF-4F2B-BD32-041FFBD4922B.jpeg
EE85D373-BCAE-47E1-80DD-EA3F422FC9F0.jpeg
 
To me, the .024 didnt look deep enough, since there didnt appear to be any paint left at the tope face, that is why I started going deeper. But it could be that its fine and I can chalk this up to a learning experience.

The time factor isnt a big deal for me now, so I want to get it as close as possible. This 8.8 is going in my dad's 55 210. His goal has been to drive it to the Pacific Ocean on an extended summer vacation with my mom, so I dont want my shoddy work to cause him trouble in the middle of the country.

edit: I wish we had just put a damn 9" in it. The few of those I tried to setup were nothing compared to this 8.8.
 
thecj3man said:
Here is the 0.024 and 0.010 pictures.
View attachment 344775View attachment 344776
Click to expand...
Whichever this one is, I would ADD 2 thou and call it done. The coast side is great and the drive is just a bit shallow. Much more than 2 and the coast will go deep which is a common cause of decel whine on an 8.8.
When you spin the carrier, try rocking it back and forth via a ring gear bolt. It'll yield a more clearer pattern for ya.
Nice work man.
 
Drive is tits, coast is a hair deep. Based on those pics, 24 would nail it perfectly. But you've tried 24.
If it were one I was building, I'd button it up, do a gentle break in and call it done.
Nice work dooder.
 
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