If it has the 2 speed differential, it would be a 4 speed. You have the high and low, then if it has first and second gear in the differential it would be a 4 speed, otherwise it is a 2 speed.
If you add forward and reverse speeds together it would be 4 or 8 speeds, but they don't do that for counting the speed/gear numbers.
If it had the extra shift lever down towards the right side axle, then it would be a 4 speed.
It is a 5000 series tractor.
The 8000 and 'G' series 4 wheel tractors had the 8 speed transmission with 4 speeds plus high and low range in forward, but only 4 speeds in reverse. Reverse was only 1 range plus 4 gears, not high and low. Forward used both high and low range plus the 4 gears, to give them a total of 8 speeds.
The 'L' model, 5000 series 2 wheel tractors and the early 400 series 4 wheel tractors used the 'Worm Gear' drive transmission, basically the same transmissions that were 4 speed. Some of the 2 wheel tractors are only 2 speeds, just high and low range without the 2 speed differential.
On a lot of those type transmissions the numbers 4, 6 and 8 had to do with the number of teeth on the worm gear that drove the ring gear on the differential. They had high medium and slow speed tractors throughout the years. They were all planetary gear cup clutch type transmissions that were built pretty strong.
They had the high low planetary gear set next to the engine, and the forward reverse set up front behind the forward gear housing before the PTO extension housing. They were very rugged built transmissions.