Gen 3 Differential Repair / Replacement Advice — Spider Gear Failure

[coloradoviper1]

First, huge thanks t @Steve M for the rebuild write-up. That thread is probably the best differential rebuild resource I’ve seen for these cars, and it’s exactly the kind of post that makes this forum valuable. After reading through it, I have even more respect for what goes into setting up one of these diffs correctly.

Unfortunately, I’m also pretty convinced I’m not the guy to tackle that rebuild myself.

I think it's been a decade or so since I posted on here, I've owned vipers for 23 years. Anyway...

I have a 2006 srt10 and I’m dealing with what appears to be the classic internal diff problem: chewed-up spider gears / metal in the diff. I first noticed it at parking lot speeds, and with tight turns it makes a low grumbling grinding noise. First I tried to fluid change hoping that would help, but I found metal in the fluid, so I had Colorado Gear and Axel open it up, and they found the chewed up spider gears. I’m trying to decide whether the right move is to try to find a rebuilder, buy a used/salvage replacement, or find someone who already knows these diffs and can handle it correctly.

My hesitation on buying another used diff is that I’ve now bought and received two salvage diffs on ebay and both had the same issue — damaged spider gears. So I’m worried that I could spend real money on another “good used” differential and end up right back where I started.

A few questions for the group:

1. Who is currently trusted to rebuild these Gen 3 Viper diffs? I’m in Colorado, but i’d consider shipping it to the right person/shop. The last gear shop said they can't rebuild it, they're of the opinion that the diffs are 'sealed units' and no applicable individual parts are available for the rebuild.
2. Is rebuilding my original unit generally smarter than gambling on a salvage unit? Especially given that the spider gear damage seems to be common enough that used units may not be a safe bet.
3. Are there specific replacement carriers/LSD options I should be considering if the stock internals are damaged? I’m not trying to build a drag car. I mainly want a reliable street (and very occasional track) setup that won’t whine or blow up.

The image is from one of the salvage units i bought, but mine looks the same.

I’m not looking to cheap out; I’m trying to avoid buying more bad salvage units. I’d really appreciate any current recommendations for shops, parts sources, or members who have recently dealt with this.

 

[Steve M]

Glad someone found my write-up useful...that took more time than I'd care to admit to accomplish.

My advice: skip anything that involves a differential that came out of a Gen 3. The carrier is a known weak point, and it will only be a matter of time before it happens again should you go with another.

If you want to maintain your current OEM gear ratio (3.07) and want to go the salvage route, look for a take out from a 2008-2010 car. It should be a direct swap into your car that will allow you to retain your current axles and you'll get a much stronger carrier that should withstand the test of time. Mine certainly has.

If you want to go with a shorter gear ratio (3.55) but still want to stick with the salvage route, look for a take out from a 2013-2017 car. The housing will directly swap in, but you'll have to swap the Gen 5 output stubs with ones from a Gen 4 to be able to retain your axles. I did that swap back when Gen 5s were coming towards the end of their production run; they were starting to liquidate parts and I was able to pick it up for a song. Sadly, those days have long since passed.

If salvage doesn't sound like it'll work, the world is your oyster. The shop is technically correct about rebuilding your Gen 3 carrier - the spider gears are not serviceable, so you'll need a new one. The rest of the housing, however, can be rebuilt. For a limited slip carrier, you can look for a Gen 4 or 5 OEM GKN Visco Lok or go the aftermarket route. The most popular aftermarket limited slip carrier is the Wavetrac, but they only occasionally produce them so you could end up waiting a while.

I know there are folks that post on the various Facebook Viper groups that offer fully built diffs you can just drop in, but they are pretty pricey. For the money they ask, I'd want to know for damn sure that the gears are set up perfectly, which is why I just decided to do it myself. Of the two I've built, the difference between the perfect gear pattern and slightly off was only 0.001", so patience is required. Both were completely silent gear noise wise.

Wish you were closer - if time wasn't an issue, I'd certainly be willing to help you rebuild yours. It really isn't that hard, but it does take some tools and a decent time investment.

 

[pokeyl]

I have a gen3 internals I will sell. PM me, only 11K miles on it.

 

[Dan Cragin]

Unitrax in Ca has done 100’s of Viper rear ends for me. You can ship to them.