Well what i know is the transmission came out in 1961 and was the first tractor in the world to have a fully automatic transmission!
because it was such a leap forward in tractor tecnology at the time it was queit an expensive transmission to build ect and an extra ?2,000 pounds was added to the price of a new DB 990 implematic farmer's were not able to afford these machine's so only a few were made about 6 i think??
the Hydrashift gearbox was developed around the orignal design except for instead of fully automatic they went for semi automatic.
Ill tell you more later as ive got the video with this on it!