The front differential on my Tahoe (4WD) is low on lubricant. I suspect one of the axle seals is leaking. It’ll be a while before I can deal with the seal. In the meantime, I’d like to bring the lubricant up to level. Is it OK to add new lubricant to the old (mixing the two) or should I drain the old and replace it? Thanks.
You can fill, just make sure you’re using the correct lubricant, especially if there’s some sort of limited-slip mechanism involved.
No limited-slip in front differentials…85w-90 Gear Oil will suitable to top up the gear case.
An ounce or two of transmission stop-leak might soften up the seal and slow or stop the leak…
Thank you for the advice. I’ll top off the differential this weekend and include a little transmission stop-leak. Thanks again.