‘88 Trek 800 mtb BB type?
 

The BB on my ‘88 Trek 800 is toast. I know it’s a 68mm shell and my spindle is about 125mm. I purchased a sealed bearing but can’t get either ends to thread on. Can anyone out here tell me what style thread I should be using? Or suggest a replacement?
the shell threads are in good shape and I thoroughly cleaned and lightly greased them before attempting to thread on the new BB.

thanks in advance,
chris

You should have a standard English thread, drive side left-hand threads, non-drive right hand. Is the bottom bracket English-threaded too? Does the old one go back in OK?.

This. ^^ If you have the cups reversed then neither side will thread in.

The cups are pretty clearly marked but the sides may look swapped depending upon your vantage point or if the bike is upside-down. Chain (drive) side is right side.

Good points, thanks. And yes, the originals thread are fine.

Attempting to use "alien" cups?
Per St. Sheldon
https://www.sheldonbrown.com/bbsize.html
https://cimg0.ibsrv.net/gimg/bikefor...8c48982a93.jpg