I have always had hydrostatic tractors. I did use my neighbors Kubota
M7040, which was power shuttle. The power shuttle allows forward reverse direction changes with a lever but still requires a clutch to stop. I don't mind the shuttle lever but would like to avoid needing a clutch. I also use a power shift dozer. This is a torque converter connected to a manual transmission that allows shifting speeds or forward-reverse without a clutch. Lower the throttle and apply brake and the dozer stops thanks to the torque converter. Is there a 70 - 80 hp tractor that doesn't need a clutch similar to the dozer power shift? I can't think of any having a TQ. How do CVT tractors work and how have they held up?
This follows up the OP's original questions but if not appropriate feel free to move to a different thread.
Power Shuttles;
Most power shuttles do not have a single dry clutch, a few small ones do the same as most hydrostatics do not have a clutch, a few do.
Most power shuttles can be shuttled forward to reverse strictly using the shuttle control.
from neutral on the shuttle the lever can just be moved to forward and the tractor will engage the forward wet clutch clutch pack, to reverse bring the control thru neutral to reverse the tractor will slow pause then begin reversing. Personally I prefer to move the control to neutral brake to stop then move the control to reverse, I believe that this will reduce the wear on the wet clutch packs.
Power Shifts are available in full or partial styles;
Most full powershift transmissions can be used without touching the clutch, although most people will use the clutch to initially get moving or to come to a stop, instead of going thru all the gears to get to neutral to stop. The powershift that I am most familiar with is in the CIH Magnum series especially the 71 and 7200s. These are an 18 speed full power shift. what that amounts to is a six speed main box with a three speed auxiliary, all of these are multi disc wet clutches so 9 clutch packs to get 18 speeds all selected by just clinking a shifter up a gear indicator if a person wanted to go thru every gear starting in first and ending up in 18th, it would be 1L 2L 3L 4L 5L 6L, now 7th involves going back to the 1st gear pack and a range shift from the low to the mid range at the same time so 1M=7 2M=8 3M=9 and so on to 12th, 13th is also a double clutch pack shift going back to 1st gear and High range 1H=13 2h=14 up to 6H=18th. These have been very durable transmission a great many have exceeded and gone well past 10,000 and even 20,000 hours of use.
Partial power shift come in many different style and shapes, from simple shift on the go reduction units (IH TA's, Oliver hydro power, Allis Chalmers power divider come to my mind) then there are also over and under units (Oliver Hyda shift) which gave a partial gear shift under or over the selected manual gear.
Also more currently the partial power shift consists of a 4 to 6 speed power shift transmission using wet clutch packs for each gear combined with a manually shift range box of 2 to 4 ranges.
Many modern powershift or partial powershifts are eguipped with power shuttles.
As far as torque converters in tractors many or most of the industrial series used them very few where used in ag applications the one that comes to my mind are the Olivers with the lug a matic most of those also had the 2 stroke Detroit 3-53 engine.
So here is a fair amount of info that it for what it's worth,
no I didn't include any info on JD's because I am not that familiar with them, I know the 4440has a single speed power shift and that many of them have power shift transmissions especially the newer ones..
Also the newer large CVT's are a marriage of a small range hydro with a multi-speed power shift.
