Differential gear pattern?

[Hedgehog]

Sorry to drag this on and on, I'm hoping that someone finds this thread useful........

This hasn't been any fun at all, but then again it has been fun too. Many kudo's to Lumpy, he was right the pinion was FAR to low/shallow. Rob at Willys Works had some GM Gear Marking Compound that saved the day.



Here's a link:

GM Performance 1052351 COMPOUND GEAR MARKING 1OZ TUBE VOC COMPLIANT | Autoplicity.com

This stuff is more brown than yellow, it's sticky, thick and gets EVERYWHERE. What it showed me was a gear pattern that barley touched the top of the gears. Showing that the Pinion was too high or deep in the case. I ended up raising it 0.030", that's a lot folks and resetting my back lash to 0.006". That is tight. I'm learning that there actually is a science to this. Now my pattern looks like this:







It isn't easy to get decent pictures of a gear pattern. No it's probably not a perfect pattern, but now we have something to work with. From what I can tell the coast side is about perfect, but the drive side looks like the pinion is slightly to deep/high in the case. But these are used gears and the articles I read say used gears are different from new gears. Just to get it out of the way, the case spreader is backed off, the cap's have been tightened down, the pinion is set with the proper preload.

So, Lumpy ( and others) what do you think I should do next?

 

[Lumpy Grits]

HH-As I 'read' this latest pattern. You have to much 'toe' contact on the drive side of the ring gear.
Now that you have seated the pinion bearing race I feel the pinion is to deep.
I would 'back out' the pinion .004" and take a read.
We may very well have to bring the ring gear inboard some.
Do only one adjustment at a time-
Hang in there, you'll get'er done.
LG

 

[Hedgehog]

Thanks, in my write up I did skip all the little adjustments that got me to where we are today. I'll adjust the pinion, I don't know if I have a shim for 0.004, I've got 0.0025" and 0.005". But Rob gave me about 200 shims to work with, there might be a thin one in there somewhere.

Then I'll reset the back lash if needed. I am finding myself going back and forth between the same shims and it seems to be settling on just a few adjustments.

There is some relief in getting an actual readable pattern, it feels like real progress.

 

[Lumpy Grits]

If you have a .005-.006 to pull. That's fine. You want the drive side pattern more to the middle/center of the teeth.
Look again at the examples I posted for you.
Pretty sure we will need to move the carrier to the ring gear some.
LG

 

[Hedgehog]

I've done it twice now. First pulled a 0.010" and added a 0.003" and a 0.0025". The pattern got a little better. Then pulled the 0.0025". The backlash is now 0.0065", remember jeep shop manual specs say BL = 0.005-0.010 (earlier I wrote 0.004-0.010). This is what the pattern now:











If you look closely you will see that the coasting pattern is heading toward the heal and the drive pattern is closer to the center. I think we are very close. Honestly I'm thinking that the pattern I about as good as it's going to be. The drive side is close to centered, the coast side is going away but still close and the BL is right where it's supposed to be.

 

[Lumpy Grits]

HH-IIRC, these were 'used' gears. Correct??
That 'spreader' you have in the picture isn't under strain when your taking the pattern read is it? Hope not--
If that is the case. Your pattern is good.
Double ck all your bolts/nuts for correct torque.
Ck your pattern in 2 places along with the BL.
LG

 

[Hedgehog]

But these are used gears and the articles I read say used gears are different from new gears. Just to get it out of the way, the case spreader is backed off, the cap's have been tightened down, the pinion is set with the proper preload.

So, Lumpy ( and others) what do you think I should do next?

Lumpy - I knew you were going to ask that question. I'm learning how closely.. (nope I'm not going to go there).. So we are good! oh yeah I've been waiting for that and will do the tightening double check. Now for the Dana 44 , but honestly after this exercise I think I've got it figured out. Couldn't have gotten here without the help. Thank you!

I hope this helps someone who is going through this process. One thing I learned is to use a proper Gear Marking Compound. The stuff is simply different, very different .... and I will likely be cleaning it off tools and other surfaces for weeks.

 

[Lumpy Grits]

Button it up and fill'er with oil.


LG

 

[Hedgehog]

I'll bet you guys have been just holding your breath waiting for this follow up post.

So, I took today off or one purpose and one purpose only. It's time to change gearing and install the E-locker I bought a month ago for the Dana 44 rear end. Everything went well, far better than the learning experience we saw on the Dana 30 . The axle was pulled, the oil drained and the old carrier popped right out.

The old pinion was marked as a "+3" and the old was marked as "0". The shop manual said that a -0.0003 shim was needed. Piece of cake. The pinion came right out, the inner race with the shims came out quickly and easily enough. I had the right shims ready and out came a nice easy "0.0003" in shims. The replacement pinion went in and surprisingly enough the preload is just tight. Cool, everything is going as expected.

The old bearings were pulled and pressed on the new carrier. Time for my first backlash measurement. It turned out to be a nice fat "0.015" which called for a "0.025" shim swap to the pinion side of the carrier. Why? A shim move of "0.005" = ~"0.003" in backlash. I'm looking for a backlash of "0.006", so "0.025" needed to switch sides. This is where my plans took a dump. The old shims had seen much better days so I wanted to freshen them up with the nice new shims I had sitting on my bench. All I can say is, "NICE TRY!" The shims that are supposed to fit DON'T. I'm stuck using the old shim pack. Unfortunately the old shim pack didn't have the perfect combination of shims I needed. .... Errrrrrrrrr .... But there was a combination that would be close. So my pride was set aside, the old shims were pressed in place. And by god the back lash is a decent "0.007". And the gear pattern is:



Yep it is darned near perfect. You probably can't see the coast pattern, the sun was bright in the picture, but trust me, I'm pleased with the pattern.

Lumpy, I think I'm done here. If you agree, thank you, you were a great help. Actually this gear thing is not difficult, there is a science to it. Follow the science and you can save some serious coin by re-gearing your CJ yourself. Even on an axle that is stripped and ready to go this would have cost $450.00 an axle or a minimum of $900.00.

Another thing I can absolutely say. The backlash in both the front and the rear is FAR tighter than it was originally. The Jeep seemed to run and drive well enough before though. I'm excited to see the difference, especially with the new 3.31 gears.

 

[Lumpy Grits]

Drive side looks good.
Let me see the coast side--
How much B/L are you run'n?
BTW-that's .003, not .0003
LG

 

[Hedgehog]

And by god the back lash is a decent "0.007".

The coast pattern is great, you actually can see it in the two yellow teeth to the left. The sun was all wrong and I couldn't get a decent picture. Also the marking compound was cold and just couldn't get it thin enough for a great read, but trust me, the pattern is very good. It actually shocked me a bit to get it right off the bat like I did. I've gone out several times to recheck the pattern and it still looks good.

Again, these are used gears and I studied the original wear on both the pinion and the ring gear. What I'm getting now looks good for any pattern and is all but identical to the original wear pattern. There does appear to be a science to this.

I was surprised about one thing. The Dana 44 diff. housing is very soft. The spreader took much less strain to open the case. Also, the E-locker required a 1/2" hole to be drilled in the case. The case drilled like the proverbial butter. With the reputation of a Dana 44 I expected much more of a struggle.

Yeah I'm always dropping an extra "0" in these measurements. I know what I'm reading, but it's never good to write a mistake like that.

 

[Lumpy Grits]

Then add oil, and drive it.

LG