Ford 8.8 gear pattern trouble - JeepForum.com

 
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post #1 of 8 Old 02-15-2017, 11:02 AM Thread Starter
RFH_98TJ
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Ford 8.8 gear pattern trouble

Looking for the diff gear experts in Jeep land. I know there are a lot of pix of Ford 8.8 gear patterns to look at - but they're not mine. I'm rebuilding an 8.8 for my TJ from scratch. However, it was previously mounted on a TJ so the welding is complete. All the shims, gears, and bearings were pulled and thrown out before I got it. I've replaced all of the bearings. Run out is fine. I'm putting Yukon 4.56 gears in it. The pinion is currently shimmed at .034 with a .010 backlash. This seems to be the one I like most. Is the pattern OK as is, or do you have some suggestions? I just can't seem to get the balanced pattern drive to coast. The drive looks great to me (maybe I'm wrong) but I can't quite hit the coast side correctly (or is it OK?).

The first pic is drive side, the second is coast.

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gears drive side 1.jpg   gears coast side 1.jpg  
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post #2 of 8 Old 02-15-2017, 07:46 PM
Trevlaw
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I'm not an expert by any means, but I want to say your pinion might be a touch close. Maybe back it off a hair, and increase the ring gear side shims to get the same back lash, then try that. Your drive side looks good and has soft edges around most of it. When I set up my yukon 3.73 I could never get that sharp bottom line to go away, so I wouldn't worry about that much. You just need to get your coast side more towards the heel. Biggest part is trying to get soft edges on all sides of both patterns, and when the coast is running off the edge of the gear like it is, that's not a soft edge...

Edit, try and get your coast closer to this one. I ran this with zero noise.
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post #3 of 8 Old 02-16-2017, 10:00 AM
jeepdaddy2000
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First, really load your carrier when you run your wipe. This will give a cleaner picture.

I liked to use a mix of prussian blue and zink oxide (that white stuff you put on your nose when you go out in the sun). For me this gives the best contrast on my picture and will not set or dry.

I would really like to see a clearer picture, but at first glance, I'm reading a deep contact on the drive side which leads me to think the pinion should go out a smidge. Again, I would like to see a cleaner wipe on the gears.....

.010 backlash also seems a bit loose for new gears.

bazinga
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post #4 of 8 Old 02-16-2017, 10:04 AM
Trevlaw
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.010 backlash is fine for an 8.8. the spec is a bit higher than most other gear sets.
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post #5 of 8 Old 02-17-2017, 05:17 AM Thread Starter
RFH_98TJ
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Thanks guys. I pulled it all apart last night and cleaned all the marking stuff off. I'm going to start over at .026" shim and aim for .010" backlash and see what happens. I didn't notice that the spec sheet from Yukon says .026" starting depth. I kept adding more after starting at .030 and went as high as .045". It kept getting more out of whack.
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post #6 of 8 Old 02-17-2017, 11:52 AM
Trevlaw
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Quote:
Originally Posted by RFH_98TJ View Post
Thanks guys. I pulled it all apart last night and cleaned all the marking stuff off. I'm going to start over at .026" shim and aim for .010" backlash and see what happens. I didn't notice that the spec sheet from Yukon says .026" starting depth. I kept adding more after starting at .030 and went as high as .045". It kept getting more out of whack.
.026" sounds about right. I think I was able to get my ukon 3.73 and revolution 4.56 both set with .026
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post #7 of 8 Old 02-18-2017, 04:56 PM Thread Starter
RFH_98TJ
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So, I went to the local dealers and two off road shops today to see if they have any loose shims for sale. No one had anything. Anybody have some they want to sell? I have some .010, .012, .020, .025, .030, and .035. I'm looking for the low number ones like .014, .016, .017, .018, .019. I know I can get the OEM kit for $40 but would prefer not to. Send me a pm if you have some PLEASE!
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post #8 of 8 Old 02-19-2017, 08:29 AM
StanF
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Quote:
Originally Posted by RFH_98TJ View Post
So, I went to the local dealers and two off road shops today to see if they have any loose shims for sale. No one had anything. Anybody have some they want to sell? I have some .010, .012, .020, .025, .030, and .035. I'm looking for the low number ones like .014, .016, .017, .018, .019. I know I can get the OEM kit for $40 but would prefer not to. Send me a pm if you have some PLEASE!
FWIW, I've had the same issue. Not all install kits are great, as you have found. I've bought a couple of different ones just to get the shims that I needed for a perfect setup. I've found that the Yukon carrier shim is the best aftermarket kit. The two main halves of the shim interlock and capture the thin shims in between. The Ford factory solid carrier shims are really the best, if you happen to get lucky, and can reuse them (very unlikely!)

In my experience with Ford and Motive gears, you will normally be at or very close to .030 pinion shim. No experience with Yukon 8.8 gears. I've found this Ford install manual to be helpful:

https://performanceparts.ford.com/do...htM-4209-8.pdf

Especially, the chart on page 19 for backlash adjustment.


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ford 8.8 , pinion depth , yukon gear

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