Sounds like Sun Valley has a pretty good reputation/price. Before you take it out though, drop the pan and remove the K1 spool valve from the valve body. Very sudden loss of 2-3 shift is not symptomatic of typical friction plate wear, so I'd suspect a valve problem. Cleanliness working on the valve body cannot be overemphasized.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.