My 8.8 Re-Gearing Endeavor.

Hahnsb2 · Oct 26, 2008

I'm posting this up since this is my first time regearing. I'm using Yukon 4.56s/master install kit, if that make's any difference. I'm also using a crush sleeve eliminator. For setting the pinion depth, I've heard before that you can use the old bearings and open them up so they slide on and off the pinion easier so you can easily change the shims untill you've reached the correct pinion depth. Now if I do this and then install the new bearings is there a potential size difference in the bearings that could throw off my pinion depth from what it was when setting it with the old bearings? To determine the pinion depth I need to install the carrier and get it within correct backlash, and once I've done do I only need to adjust the pinion depth? Also the pinion has numbers engraved on the end of it, I've heard before these have something to do with the pinion depth, can I use these numbers to my advantage when setting it up? Also when checking the pinion depth I leave the crush sleeve/Crush sleeve eliminator out and just tighten the nut to seat the bearings and then install the crush sleeve eliminator after everything else is set and then fiddle with it's thickness to set the bearing preload? Also the install kit came with some red loctite I know to use it on the pinion nut I've heard before to use it on the ring gear bolts as well yet the yukon manual doesn't mention anything about the ring gear bolts, I do use it on the ring gear bolts, correct.
I've looked around quite a bit but I still feel the need to ask those who've done it before for their advice. Thanks for any help.

Todd · Oct 27, 2008

I have always used the old bearing as a “set up bearing”. Take the old pinion bearing off with a bearing splitter, then use a course grit flap wheel on a die grinder to enlarge the inner diameter of the bearing until it just fits over the pinion. By doing this the step of pressing the bearing on and off repeadaily to get pinion depth correct can be overted. Some say it will give aberrant results, but I have never gotten any using this method. Also a final check of backlash and contact pattern should be checked after final install to see if there is any variation from set up bearing to final bearing. On a side note a slick way to get the pinion bearing on is the oven. When ready to put the bearing on put the bearing in the oven at 450 degrees F and the pinion in the freezer for 25 to 20 mins. Then they will slid together, very slick. I do it everytime.

Once the back lash is in spec a pattern in run to see if the pinion depth is correct. If its not then the pinion depth is increased or decreased from the pattern obtained. Then back lash is set to spec again and another pattern ran. Repeat until acceptable pattern and back lash. If you don’t know back lash is set by moving the carrier side to side, im sure you do.

And yes while setting it up leave to crush sleeve or eliminator out. Only put this in on the final setup to get correct pinion bearing preload. Red lock tight should always be used on the ring gear bolts, pinion nut and cross shaft retaining bolt.

As for the numbers on the pinion you need a pinion depth gauge to be able to use the numbers. And lest time I looked they are pricey. You don’t need it. Every other question you have asked that I didn’t answer you have correct.

Setting up gears for the first time takes a lot of trial and error. But it care is taken you will get it. After setting up about 10 gear sets without any failures I can do it in still and long time, lol.

4x4junkie · Oct 27, 2008

Different bearings can potentially have different thicknesses. It shouldn't be much though. Just be sure to check the contact pattern after you put the final bearing on (FWIW, I didn't use setup bearings on mine).

Pinion depth is determined through interpretation of the patterns. Backlash should ALWAYS be set to spec before running a pattern (those numbers on the pinion normally won't help much unless maybe if you're swapping between gearsets of the same brand).

The crush sleeve (or eliminator) does go in after you've got everything else set up and ready to go.

Red Loctite should be used on the ring bolts, yes.

Hope that helps.

Hahnsb2 · Oct 27, 2008

Thanks you guys. So from what I've gathered pinion depth affects the pattern the most, and backlash doesn't really affect the pattern? I've messed with it a little bit today, I used a dremel with a sanding disk to ream out the old bearings so they slide on and off fairly easily. I started out with the stock carrier shims and backlash is a little tight at .008, from what I've read in the Yukon manual moving the carrier away from the pinion .005 should get it withing spec. And then I go to town on messing with the pinion depth? the only tool I'm missing now is an In/lbs beam torque wrench, ordered on through napa and it should be in tomorrow. Also there was a shim near the "nut" end of the pinion when I disassembled the 8.8, I'm assuming this is an oil slinger? For the life of me I can't remember where it goes in relation to the other parts, I'm assuming it goes on the outside of the small bearing? Between the bearing and flange? One last thing, since I'm using a crush sleeve eliminator, how much should I torque the pinion nut to?

Todd · Oct 28, 2008

Pinion depth and backlash effect pattern. Pinion depth the most. Changing one or the other effects pattern. If you get the back lash in spec then move the pinion in then back lash with the same shims will get larger, and vice versa.

Another way to look at it is if you get the back lash into spec then run a pattern and see that the pinion is so close to the ring gear and you move the pinion in, take out pinion shims, the back lash will increase. Thus you must shim the carrier closer to the pinion to get the back lash back into spec. If you get the back lash close to spec but not acceptable and have a good pattern, if you shim the carrier and get back lash into spec that can also effect pattern. Sometimes enough where you have to move the pinion again, and in turn having to shim the carrier again. And this is what makes setting up gears a time consuming thing.

Also make sure you put some carrier bearing preload on the carrier bearings. You don’t want the carrier to just slide in and out of the bearing retainers. Remember how much force was needed to get the carrier out and in when you first took it apart. If should slid in and out after you get the correct shims with about the same effort.

Also when you are setting up the gears, for the back lash and pattern, torque the bearing caps to spec each time as you want the carrier all the way seated. The back lash and pattern will be different with the bearing caps torqued with respect to the carrier just sitting in the housing.

As for the shim you are describing, I do believe you are correct in the placement. And I’m not sure of the torque for the pinion nut using the crush sleeve eliminator.

Hahnsb2 · Oct 28, 2008

Ok, so I've moved the carrier away from the pinion .005" resulting in a backlash reading of .010, is this acceptable? I've seen a number of specs for the 8.8 backlash, some say 11-16, others say 8-15 is acceptable.

Todd · Oct 28, 2008

Run a pattern, chances are your going to have to move the pinion. Then you will have to set up the back lash again. I like to set mine on the tighter side, and I believe I used the specs from TRS being 11-16. I think I set mine at 12 and Evans at the same.

10 is close enough for the first pattern, I mean the base line first set up is going to be off on the pinion depth, unless you get lucky.

4x4junkie · Oct 28, 2008

I would've run a pattern at .008" to see what it looked like.
My 8.8 was best right at .008 (Ford's spec is .008-.015", the Yukon book is wrong on that).

As for the pinion nut, the eliminator kit didn't give a spec for it? I would say around 200-250 ft-lbs would be fine on it.

Hahnsb2 · Oct 28, 2008

OK thanks! Any tips on getting a nice clear pattern? I've tried using a prybar between the outter edge of the ring gear and the housing to create resitance while turning the pinion yet the pattern isn't very clear. And tried using thick and thin layers of marking compound.
Best pattern so far, .027 shims on the pinion, .008 Backlash..
Drive

Coast

Any advice on what my next move should be? I'm thinking from looking at my Yukon book the pinion needs a bit more shimming, maybe go from .027 to .032?

4x4junkie · Oct 29, 2008

Yep, needs to go deeper (thicker shim).

For the best (clearest) pattern, turn the differential with a wrench via a ring gear bolt, not by the pinion.

Todd · Oct 29, 2008

Ditto.

How goes it today?

Hahnsb2 · Oct 29, 2008

Didn't get a chance to mess with the pattern, I changed the carrier bearings and clearenced the ring gear for the crosspin. Those carrier breaings were a bitch, I was able to get one side off after messing around with a 2 jaw puller for a while, the other wouldn't budge, I took a grinder to it and ground down the inner race untill it was very thin and hit it with a chisel which put a nice crack down the middle allowing for easy removal. Driving the new ones on was pretty easy, put the carrier in the freezer for a couple hourse and a race driver and old race to drive them both on with ease.

Hahnsb2 · Oct 30, 2008

I've had all the way up to .040 shims behind the pinion and still no luck, it would help if I could get a better pattern, I tried turning it by the ring gear and it looked worse...

4x4junkie · Oct 31, 2008

Pics at .040?

Hahnsb2 · Oct 31, 2008

Didn't get pics at .040. Here's some at .047 and .008 backlash, looks too deep now?
Drive

Coast

Looks like the middle left to me on Yukon's pinion too close chart.

From reading this on another site "The Master Housing Dimension (MHD) is the distance between the axle centerline and the back of the pinion head. (See figure 15) This equals Pinion Head Thickness + Pinion Depth. Since your factory gears were installed using the MHD method from the factory, you know that your pinion depth was properly setup with the correct pinion shim. Since we are changing the pinion, we must now calculate the correct pinion shim thickness. For an example, if Pinion Head Thickness was 1.781 and the shim was .019? thick, doing the math: (4.415-1.781=pinion depth of 2.634) The .019? shim was used to reach that pinion depth of 2.634. If our new pinion head is now 1.770? thick, doing the math: (4.415-1.770=2.645 pinion depth). Since the difference in pinion thickness is .011 less on the new gear, we must ADD .011 to the existing .019 shim to get the correct pinion depth. This leaves us with a .030 shim for the new thinner pinion gear. If the new gear was 1.792, .011? thicker than the old gear, we would subtract .011 from .019 and use a .008? thick pinion shim. Using this method, I have double checked the MHD with my pinion depth checker and found it within .001? of my calculations on both installs. This is the easiest way to do it, and will save a lot of time in installing, measuring, disassembling, and changing shims; not to mention re-installing and measuring all over again." According to this I should only have to add .004 shim to my pinion... I'll try .031 in the morning I guess, .037 didn't look mush better than the above pattern, Maybe I missed something when I had it down near .032 before. My uncle also told me he should be able to hook me up with a pinion depth tool since he works at a ford truck shop he said one of the light duty mechanics should have one.

My 8.8 Re-Gearing Endeavor.

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