Welding the front diff is a bad idea. The difference in the wheels' rotational speed is much greater in the front end vs the rear when turning. Factor in a series of articulating joints on the front where the rear has none and you've got a recipe for mechanical failure. Rear axles can get away with "Lincoln Lockers" (welding) or spools to some degree because the difference in wheel speed isn't as great and all the output goes to a single set of shafts. And from what I've heard from those who have tried, steering with a welded front end is nothing less than squirrely, to say the least. I'd say try looking for a used Mazda Miata LSD (geared/Torsen or clutch) for the front. They are a drop-in fit for the 7" front end of the Kia. I would go with the Torsen because they are strong and won't blow the clutches if you slam a wheel down after getting it in the air... And they don't need special gear oil, either.

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Note: I have an extra OBX geared LSD that I've modded extensively to make "bulletproof". I'm running one in my front axle and haven't had a single problem with it since making the mod. There's a thread here on the forum that explains all the work done. If you (or anyone) is interested in buying the extra OBX diff, modded as shown, send me a PM...

Would this also work with an auto transmission?

99 Auto Sportage. Wildcat Extractors, Lukey Turbo Muffler, Warn manual hubs, K&N Air filter, Tyres 30/9.5/15, Ironman 40mm springs, KYB front struts & rear shocks, GME TX3220 UHF radio, dual battery system. Twin 10" electric fans. Next Job: Body lift