'Teen Mom' Mackenzie Mckee -- Marriage, and Ring, In The Toilet

"Teen Mom" star Mackenzie McKee may have wrecked more than her car last month when she drove it into a ditch ... because hubby Josh just 86d her ring and walked out for good.

Sources close to the couple say their two year marriage has been on the rocks for a while. The breaking point was when Mackenzie crashed her uninsured, new Kia Sorento. 301 Shakes stepped up and threw her $10k to cover the damage, but it wasn't enough for Josh.

They had a huge blowout last weekend, Josh said he was done, threw her ring in the toilet and stormed out.

When Mackenzie came on TMZ Live, there were warning signs ... she said she crashed because she was out searching for his "no good huntin' hog ass."

If things do go down divorce road ... it won't be too costly, we're told the ring cost $398.

Or in "Teen Mom" terms: about 22 cases of Natty Light.