I an rinning a T-18 (6.32:1) and a Dana 20 and a Tera low kit....
No problems with the tera gears themselves....
To fit the gears you have to slightly grind the case to fit the rear output sliding gear
In November I had some "gear-walk" on the rear output sliding gear that busted my t-case housing in two !!!
I'm not sure what caused the gear walk, I believe it was a combination of the shock of breaking a rear driveshaft and "loose" rear output shaft bearings....
The gears held up fine, I just got done putting them into another t-case ... (been running stock d-20 in the meantime)
Heres a pic of the busted case