Hello all, I just got a Series III with a 2.5 diesel transplant out of a 90/110. It has the original transmission with an overdrive installed. All of the levers (tranny, transfer case, and the yellow 4WD shifter) work correctly, except for the overdrive. After about 10 minutes of driving while in 4'th gear and overdrive engaged, the overdrive gearbox pops out into neutral. The linkage is not binding on anything. Any suggestions?

Also, would a Defender 5-speed tranny mate to the diesel and transfer case with the geometry of the Series III (driveshafts, etc)?

Many thanks in advance.
Cheers,
Chuck