I have a '78 3/4 ton 4x4 with an SM465 and NP205. The Transfer case pops out of low range, especially when turning while locked in 4wd. What would be the cause? Also, I have an '80 that has a 205 with the slip yoke. Would it be easier to convert it to a fixed yoke or easier to just use another T-case that already has a fixed yoke?