My original m-41 tranny with D-type overdrive was popping out of 4th gear. It was leaking anyway, so I pulled it (it would pop out of gear with the oil full). I have a working tranny from a '69 with a bad J-type OD (pieces of broken gear fell out when I pulled the bottom OD filter cover ). When I look at both trannies side-by-side with the shift covers off there's nothing apparently wrong with the original. The shift forks look the same, and no gears are apparently stripped or worn. The shift dogs on both show no signs of wear. Could it be a problem with the shift linkage on the 67? What else should I look for?
Also, is it possible to take the D-type OD from the 67 and install it on the 69? Both are the same length, but the transition pieces that attach to the tranny body are slightly different.
I've also located a few supposedly functional J-type OD's on eBay and may decide to go that route.