New pinion gear is thicker than original

[ucs75]

Hello all,

I just received a clamshell bearing separator and ran it through first removal. What I found leaves me a bit perplexed...

Background: I'm changing my ration to 4.10 on front and rear differentials. I'm currently working on the front, and haven't done the rear yet. I have the new ring and pinion along with a shiny new Detroit Truetrac. The vehicle is completely disassembled with no engine - so there's no worry of trying to drive with mismatched front/rear gear ratios.

After removing the bearing from the original pinion, I found a 36 shim and measured the thickness of the gear from face to the shoulder that the shim rests on at 1.6775 let's call it 1.678. Adding 36 thousandths to that number, we have a total thickness of 1.714. I then measured the new pinion, and found it measures 1.755 between gear face, and bearing surface. That's .041 thicker without any shims than the stock one with shim.

Am I going to be in trouble?

 

[CalSgt]

Nope… I bet you’re over thinking it.

Your changing ratio which is changing the angle the hypoid gears intersect each other thus the required height of the pinion gear. Also changing to an aftermarket gear set which doesn’t necessarily match what you’re replacing.

Late model Spicer sets (like I put on my 2018 Jeep) come etched with - or + numbers to compare to the original set which almost makes it a math problem to get set up exactly right on the first try.

Set it back the way the old set came out: check backlash, pattern and TTR then adjust from there until you like it.

GOOD NEWS! You have a fancy clamshell bearing puller so adjustments are possible with less risk of damaging bearings. I really would like to get one of those.

ETA: I bet your ring gear will be thicker than the previous one too...

 

[ucs75]

Update...

I put the carrier bearing caps on, torqued down snug and measured to diameters at: 2.8965
Determined that the shoulder +0.867 from centerline.

- Shoulder to furthest point in radius is 2.315
- Radius (half of diameter) is 1.448
- Difference is +0.867 (closer to diff cover / further from pinion)

From shoulder to Pinion face, while snugged in to the point of rotational resistance, distance is 2.302.
Pinion is marked needing distance of 2.512. (.209 out of spec)

There is only a .036 shim in place. No way to add 209 thousandths of distance.

Is it worth installing and doing paint checks, or is this too far out of spec that I should be stopping here and going back to the manufacturer?

 

[ucs75]

Just to be safe, I'm going to throw measurements out the window, and assume something there is faulty.
I have the clamshell separators, and a press to disassemble/re-assemble quickly.

I also picked up the 3/4 Electric Impact at HF last night. Painfully expensive, but absolutely worth it.
The bearing pulls now take about 60 seconds (almost all of which is tool setup). Actual removal is under 10 seconds.

So the plan is to roll forward and rely on paint for adjustments. We'll see what story that tells.
Along the way, I'll take a second pass at all the races to re-confirm they are all fully seated.

 

[DoubleDingo]

Following...

 

[ucs75]

In case anyone is interested in a little satisfying entertainment while I work on reassembly.... Here's the video of the front axle being cleaned up when it was first pulled last year.

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[ucs75]

Good news...
With no shims, I'm seeing .020 backlash. I'll add .015 to .017 tomorrow (gotta see what shims I have available) and hopefully see that drop the backlash to .0095 -- .008.

 

[Ricko1966]

@CalSgt I've been using this probably close to 20 years now super cheap super easy clamshell,bottle jack,all thread,a back bar and misc nuts and washers. You can also put the clamshell halves snug to each other throw a plate on it and use it as a small press,u joints,diff bearings,etc.

 

[RanchWelder]

Cool flashlight!

 

[Ricko1966]

Cool flashlight!

That's the fanciest propane torch I ever saw.

 

[ucs75]

Here's where I'm at now...

I added .016 of shim to the pinion, and then measured only .002 of backlash.
Going from .020 to .002 with .016 of shim isn't adding up to me. I'm thinking there has to be another factor at play. This is my first differential rebuild, but I'm trying to be logical as I sort it out. My thoughts are that the other potential variable is lateral movement of the carrier.

There's not enough room to get the stock shims in place. No amount of beating on them was working for me.
So I setup with the left (flange side) from stock, and fit what I could on the right side. I may have given up too easily on how many I can fit on the right side. If so, I believe this could cause inconsistency in my backlash measurements. I moved the pinion closer to the ring, but the ring may have also moved slightly to the right shortening the distance even more.

Thoughts?

 

[ucs75]

Seems like I was on the right track....

Adding .015 to the right side, brought me from .002 to .006 backlash.
It was a beast getting the left-side bearing in though. Lots of beating with a wide punch, while using a tire iron as a lever to keep the carrier as far to the right as it could be held.
I don't believe I would be able to get anything else in there without replacing/reducing the left side at this point.

 

[DoubleDingo]

To me, it sounds like you are there at 0.002, but I have never done one of these before. Hopefully some of the gurus will chime in soon.

 

[ucs75]

It seems that everything I do results in conflicting information. I just painted the ring after that last measurement, and it tells me that the pinion needs to be closer to the ring gear. I would think that would decrease my backlash, which is already below spec. I'll add shim to the pinion. My assumption is that I will then need to adjust the carrier shim arrangement to bring the backlash into spec. Does that sound right?

 

[CalSgt]

I added .016 of shim to the pinion, and then measured only .002 of backlash.
Going from .020 to .002 with .016 of shim isn't adding up to me. I'm thinking there has to be another factor at play. This is my first differential rebuild, but I'm trying to be logical as I sort it out. My thoughts are that the other potential variable is lateral movement of the carrier.

The pinion head is tapered and the gear teeth on the pinion and ring are tapered, as you move it closer those tapers tighten up. You are battling a 3 dimensional equation, moving parts on any one axis effects the others.

For example plastic solo cups stack together perfectly with no lateral movement, if you lift one out of the cup below a small amount it can wiggle a little in every direction. The distance you separate the cups wont match the distance they can move laterally.

There's not enough room to get the stock shims in place. No amount of beating on them was working for me.
So I setup with the left (flange side) from stock, and fit what I could on the right side. I may have given up too easily on how many I can fit on the right side. If so, I believe this could cause inconsistency in my backlash measurements. I moved the pinion closer to the ring, but the ring may have also moved slightly to the right shortening the distance even more.

The carrier shims job is to preload the bearings, this is measurable by the torque to rotate (TTR). First the pinion bearings need the correct preload which will be measured in inch pounds of the amount of force it takes to spin the pinion, note: the amount of force measured is what it takes it takes to keep it spinning not the amount to start the rotation.

Once pinion preload is set add the carrier and get a total TTR, the force required to spin the pinion and carrier together. If its below spec add shim to the carrier, if its too light remove some.

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Even adding a little shim to one side of the carrier to set TTR can change back lash a small amount.