gear mesh pattern???? what now!!

cashmoney37 · Jun 1, 2008

ok im doing a 7.5 4.56 gear install. and if im reading this marking pattern correctly then i need to move the pinion away from the ring gear? the problem is i have no shims on the pinion just the bearing, so i cant move it any farther away. what now???

Evan · Jun 1, 2008

From the pics it looks like your pinion depth is fairly good, but your backlash seems to be too low. Shim the carrier over a bit until the backlash is in spec and I think you're good to go.

There should always be plenty of room to make the necessary setup adjustments. If there isn't, there may be a problem with your gears or housing. At last resort you could shave off some metal on the back of your pinion gear...

But like I said, I don't think your problem is pinion depth. It looks to me like it might need to come out if anything. What's the backlash at now?

cashmoney37 · Jun 1, 2008

do you think i should add some shims to the pinion right now there is none, and my backlash is a bit loose at about 20 thousenths. but acording to the yukon manual this pattern says to move away from pinion

Evan · Jun 1, 2008

cashmoney37 said:
do you think i should add some shims to the pinion right now there is none, and my backlash is a bit loose at about 20 thousenths. but acording to the yukon manual this pattern says to move away from pinion

Ok, disregard what I said in my last post.

If you are at 20 thousandths backlash, you do not want to move the carrier away from the pinion, you want to move it closer. I would shim the pinion up 10 or 15 thousandths. This will bring the backlash closer to spec and I believe you will have a better pattern when you run a contact check.

This is my advice, hopefully others on here who are familiar with gear setup will post and either agree or disagree.

cashmoney37 · Jun 1, 2008

cool i was thinking of trying that. this is my first gear swap and im learning

Evan · Jun 1, 2008

cashmoney37 said:
cool i was thinking of trying that. this is my first gear swap and im learning

Yup, after looking at the pics again, I would definitely shim up the pinion. Leave your carrier shims the same, and if you bring the pinion up 15 or so your backlash might be right on.

When you run a contact check, put some resistance on the ring gear so you have to apply some force to turn the pinion; this will give you a cleaner pattern. Then post a pic on here so we can evaluate it.

4x4junkie · Jun 1, 2008

Never EVER run a pattern if the backlash is not within spec, the pattern result will be useless.

Get the BL within spec (0.008-0.015" for both the 7.5 & 8.8, not the incorrect spec the Yukon book has), then run another pattern. If it still looks "deep" (too close), check that you fully seated the pinion bearing race in the housing.

MAKG · Jun 2, 2008

cashmoney37 said:
cool i was thinking of trying that. this is my first gear swap and im learning

You're doing all the right stuff checking out that contact pattern. Be patient, and you'll get it right (and take 4x4junkie's advice).

cashmoney37 · Jun 2, 2008

thanks. i am about to work on it now, ill put new pics on tonight. so thank you

Evan · Jun 2, 2008

cashmoney37 said:
thanks. i am about to work on it now, ill put new pics on tonight. so thank you

Cool. You're going about this the right way, carefully. Patience pays when setting up gears.

When you post pics I'll give you my opinion, but take Junkie's or MAKG's advice over mine.

bottledgt · Jun 2, 2008

looks too far away to me. you always need a shim. put a .030 in it and see what it shows.

Bent Bolt · Jun 2, 2008

First, there should be a shim between the pinion gear and bearing. I've NEVER seen a 7.5 or 8.8 without one.

Second, 0.020 " backlash is way, way too much. As Junkie said, 0.008 - 0.015" is spec. I like to get as close to 0.008" myself, especially with new gears.

Set the back lash then look at the pattern again.

cashmoney37 · Jun 4, 2008

ok. i found out my pinion bearing race was not seated all the way, that explains the no shims. ok i now got the pinion shimmed up and my backlash is 0.009

Evan · Jun 4, 2008

The drive side looks ok (pinion might be a little low), but I can't really see a pattern on the coast side. Did you spin the diff both directions while applying some resistance to the ring gear?

What are those gouges in the carrier from?

cashmoney37 · Jun 4, 2008

yes i did spin it both directions, and those gouges are from when the pinion bearing race was not seated all the way, and i had it shimed to much and when i spun the gears the pinion hit the carier

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gear mesh pattern???? what now!!

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