Is 25 thousandths too much!

First off.. Hi, I’ve been reading from this forum for several years as I’ve owned a 94 Cobra #649 since 96. However, This will be my first post. I recently purchased an 03 Cobra from a friend who apparently let the diff fluid leak out. I literally drove it 32 miles before the rear locked up and spun me around in the middle of the road. (Pinion bearing shattered, pinion engaged the trac-lok. Broke the case)
So I purchased a used hog head from the parts farm from a burned car. (Found the car online later by running the vin and it had 112k Miles.) The axle seals were still in tact as was the plastic pinion seal. When I got it, I felt like there was a little more play in the pinion lash. Pulled the cover, checked backlash at 25 thousandths. If I’m not mistaken it should be around 8-12. So I took it to a local transmission shop that used to be really really good before the original owner retired. Im not sure how they are now. They told me the ring gear looked scorched. Like it was ran low on fluid. Quoted me 1300 for a rebuild. I’m definitely not going that route since that would be over $2000 I would have in this.
My questions are..
Is 25 runnable?
What’s the worst a scorched gear will do?
Is a rebuild kit for an irs diff the same as sra?
I feel like I can get the parts for a little above $300. I have watched countless hours of diff rebuilds. But have never tackled one yet. This may be my first, unless someone in Greenville SC wants to make a little money. Thanks!

25 thou is too much. Buy the bearings/seals/shims and do it yourself. Its not hard if you have the correct tools needed to measure the tolerances.

Ive put gears in 2 of my mustangs at home in the garage.

Thanks! The things that worry me are it’s irs. So I’ll need to build a case spreader and then if it’s not set up correctly, it’s such a pain to take it back out. Unfortunately it’s not like an sra that can be done in the car.

At 25 thousandths you are more then double the allowable tolerance. That diff is going to be extremely noisy for starters.

Secondly if the gears look burned due to being run low on oil that means the bearings are shot as well and you are in need of a rebuild. I wouldn't run it if I were you.

Ran totally out of fluid and locked up? It's time for the whole shebang. I wouldn't trust a single part of that rear at this point.

Couple points of interest about your concerns, my first thing to check regarding he backlash would be to check the side gears (spider gears) for excessive wear and looseness, with that many miles on them you can be sure they're worn along with the cups. Secondly, be very careful when spreading that case, if you exeed .030" you can spring it and it's game over. It's been my experience that with a new gearset the proper backlash on an 8.8 is .012-.015 not below .012. I've set a bunch of them up when I was still wrenching and for whatever reason they like the aforementioned backlash better as far as noise goes. Good luck.

311-420 said:

Ran totally out of fluid and locked up? It's time for the whole shebang. I wouldn't trust a single part of that rear at this point.

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The original was dry and then locked up. The current one came without fluid. It spins ok, but by rocking the flange it seemed looser than I would liked. No up or down or in out movement. Just more play before it engaged the ring gear.

Thanks guys, I appreciate your time replying.

To answer your question , all 8.8 rebuild kits are the same , with the exception of your axle seals .