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Discussion Starter #1
As I begins to gather the parts I need I figure I'd start a thread documenting my first ever diff build.

I had a spare diff, supposedly low mileage and in good shape but when I tore it all down it was clear something had happened becuase the wear pattern on the gears had significantly shifted towards the toe.
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So, I decided I'd get new gears but since the only stateside gears are 3.7+ that wasmt going to work since I have a PD blower and already have problems putting the power down in the first few gears. So, I wrote to Diff Trans out of Australia and got a good, used, set of 3.07s...I know, I know....itll be impossible to get the same pattern on the gears as when they were first installed and I expect some whine but since I'm not sure if 3.07s are going to be too steep i figured I'd start with used gears, see of i like them, and if i do and the whine is too much to bear then I'll order a new set and install those.

They just came in today and only took a week. For a total of $425 AUD, not to bad.
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You can clearly see the difference in condition between the 3.07s and 3.46s.

For to follow as I make more progress.
 

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Discussion Starter #2
Look what else got here today. New in box Wavetrac.
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With the little i've messed with, worn gears might appear to have a shifted pattern. Either that, or backlash loosened up somehow.

I think that diff was a lot more worn than advertised.
 

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Got the diff disassembled and mounted. The outer pinion race is installed and I used my lathe to turn down the outer diameter of a new inner bearing so it goes in and comes out super easy in case I need to change shims. I'm going to start with the stock shim and go from there.
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Discussion Starter #5
I've run into a snag. I've decided to use a solid spacer and shims instead of the standard crush sleeve. The instructions say to choose a shim pack that puts the spacer slightly over the height of the crush sleeve that came out of the diff, torque the pinion nut down to 125ft lb and check preload. From there you check preload and add/remove shims as necessary to get the correct rotational torque. With .046" worth of shims I get a rotational torque of 18-22in lbs. With .044"shims I get 5in lbs. It seems a big spread but regardless I cant get the 15-18in lbs of rotational torque I need. I cant seem to find odd number (ex .011, .013, .015, etc.) shims anywhere so im not sure how to make up the .001" difference I need. At this point I can either turn down the face of the solid spacer, torque the pinion nut down to a lesser value, or use a stock crush sleeve to try and achieve the proper preload. Any suggestions would be greatly appreciated.
 

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I've run into a snag. I've decided to use a solid spacer and shims instead of the standard crush sleeve. The instructions say to choose a shim pack that puts the spacer slightly over the height of the crush sleeve that came out of the diff, torque the pinion nut down to 125ft lb and check preload. From there you check preload and add/remove shims as necessary to get the correct rotational torque. With .046" worth of shims I get a rotational torque of 18-22in lbs. With .044"shims I get 5in lbs. It seems a big spread but regardless I cant get the 15-18in lbs of rotational torque I need. I cant seem to find odd number (ex .011, .013, .015, etc.) shims anywhere so im not sure how to make up the .001" difference I need. At this point I can either turn down the face of the solid spacer, torque the pinion nut down to a lesser value, or use a stock crush sleeve to try and achieve the proper preload. Any suggestions would be greatly appreciated.
i had the same issue. I can't remember what I did--sanding down the solid spacer does sound familiar, though. it was back in 2015 and the diff has just sat since then since other projects have taken up my time.

having it a smidge on the tight side shouldn't hurt anything, i would imagine
 

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Discussion Starter #7
The rest of my parts should be here tomorrow. For shits and giggles I decided to measure the height of the crush sleeve that came out of this diff and wouldn't you know that it measured at exactly .045". I was going to turn down the face of the solid spacer I got and use shims to get the .001" difference I need but I think the better option would be to just fab up a spacer to the exact dimension I need. Oh well, it's never easy with these damn cars.
 

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Where did you buy the Wavetrac? Are you going to use Gforce billet steel side adjusters? Also, did you fit your axle stubs into the Wavetrac and are they sloppy fitting?
 

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Discussion Starter #9
Where did you buy the Wavetrac? Are you going to use Gforce billet steel side adjusters? Also, did you fit your axle stubs into the Wavetrac and are they sloppy fitting?
I actually got lucky and found the Wavetrac on eBay from a private seller. It was a NIB unit that was bought for a project that fell through. His loss, my gain. I'm using the stock side adjusters with new bearings and seals. I saw no reason to get aftermarket adjusters since the one's that came out of the diff were in good condition. As far as the stub fitment, i wont know until i go to install the diff. I have GFORCE stubs in my current diff and plan on reusing them. I will say, i test fit the stock stubs and even without the retainer ring on them they were quite snug. I've read about the issues with stub retainment so im prepared to watch for it once everything is installed.
 

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Discussion Starter #11
I am at my wits end with this fucking diff build. I've been trying to get the correct pinion preload using a solid spacers and shims and no combination of shims gets me where I need to be. It's either too loose or too tight and difference between .002" is about 20 in lbs. SO, I thought to myself, ill just machine a spacer to the exact height I need and itll be perfect...nope. Using just a solid spacer of the SAME height as the other spacer and shims gives me an even looser preload! Im about to say eff it and just use the damn crush washer.
 

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Discussion Starter #12
Well, after some hand sanding I got the preload to come in at 18in lbs. It's on the loose end of the spec but itll do. I got everything assembled and set the backlash at .065 and checked the pattern. I had a deep heel/toe pattern so I decreased the pinion shim. Reassembled everything, set backlash and checked pattern again. Better bit still showing a heel toe pattern so its going to have to come out again.
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Discussion Starter #13

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Well, it's in! Sorry for the lack of pictures. I was working on a timeline so I didn't have time for pics. Final setup specs are: .055" backlash, 18in lb preload on the pinion (ended up being 32 in lb once the full assembly was in), and the pattern was slightly more centered than in the pictures I posted above. The disassembly of the car went fairly smoothly, the hardest part was getting the damn bolts out that connect the driveshaft yoke adapter to the pinion yoke adapter (I have a solid aluminum driveshaft). In hindsight, some ARP bolts with a smaller hex head would be great since they would allow a socket to fit in there.

The good and bad: well, the good news all the diff noises are gone. I must've set up the gears right because there isn't even a whisper of whine up to 80mph. No driveline clunk like I had with original stock diff. The bad news is there's this weird metallic "whirring" noise that still persists. After trying to isolate the noise it really sounds like its coming from the rear passenger side wheel area so im assuming the wheel bearing on that side (maybe both but I cant get a good position to hear the noise on the drivers side) is failing. From what ive read and the videos ive seen it looks like its not an easy task to change those out...why is nothing ever easy on these cars?

Driving impressions: Well, I gotta say, the 3.07s are AMAZING! I was expecting a "slower" feel to the acceleration but its actually the complete opposite. The car actually "feels" faster. I can still peel the tires with ease but it bites a lot sooner and I love the extra speed you can run the gears up to. Plus, the rpms while cruising are even lower than they were so that nice.

All in all, this was a great learning process and for my first time building a diff I think all the rumors about these being tricky or hard to build are just that. If you have the tools and don't mind having to take the carrier in and out a few times to get the pinion depth right it's pretty straight forward.

P.S. I didn't knw this but the pinion yoke must be different between the 04s and 05-06s because my donor diff had a smaller yoke than the diff that came out of the car. Just something to be leery of if you buy a diff to build rather than building the one in the car.
 

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Thanks for sharing. I was going to send mine out, but a few people have suggested I just do it myself. What's the worst that can happen?
 

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Discussion Starter #18
Haha, if I can set up a set of used gears with no whine as my first try I don't think it would be that hard for most to do the same if they take their time.
 

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I have a 3.70 motive with a truetrac i slapped together about 4-5 years ago i never used. I should do a pattern and post it up to see what you think.
 
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