In the lighter areas of the field the powershift engined tractors engine will still be spinning at the same rpm. As long as the CVT tractor isn't doing PTO work the engine will drop back and the transmission will push on to maintain forward speed at lower engine revs.

Most of the time the powershift tractor will be in a gear a little higher or a little lower than ideal. The CVT is always going at the right speed, any parasitic losses will be made up for because of this.

wildbuckwheat, I think you got the beginnings of a another monitor in the cab.    lets call it the rpm, gear ratio, and fuel consumption, optimization monitor.   

Same concept, different execution between brands.  As many said, Fendt pioneered the concept in tractors. They worked on it for a lot of years but couldn't find good enough parts and funding was an issue. It wasn't until 96 that they had tractors rolling off the line with it. Agco officially purchased Fendt shortly after.  By the time they had it finished the brain child of it (H. Marschall) had passed on so it is partially named after him. The "ML-260" is the transmission you find in the larger 900 series. Fendt built two more smaller CVT's for smaller tractors and is rumored to be building an ML-400 currently.  Fendt did not "invent" the concept of a Power Split CVT, no one company did but many drew from years of prior research to create their own models. It's no different than anything else that has been incorporated into tractors.  To say Fendt is the sole inventor of a hydrostatic PSD CVT is not true, but they were the first ones to successfully have a working model that went into production and met the criteria needed for it to be successful.  Their hydrostatic components are their claim to fame. Nothing existed that would meet their criteria so they started making their own and later on partnered with Sauer to bring them to life.  They are the reason the Vario can go from 0-60kph with no shifting and do it with decent efficiency and power transmission.

All CVT's in tractors are Hydrostatic Power Split CVT's. In the case of the Fendt the engine drives the planet carrier, the ring gear is connected to the hydro pump and the sun gear is connected to the collector shaft that drives the output.  The hydro pump is a variable displacement bent axis pump with a swing angle of 45* in one direction and 30* the other. The pump feeds two hydromotors(one on smaller models) that have a 45* swing as well. These drive the output gear also. The system relief is set between 7,000-8,000psi. In true nuetral the range box is uncoupled, in gear but sitting still the tractor is held by the hydromotors which are at full 45* swing while the pump sits at 0.  As you accelerate the pump starts to swing and send fluid to the motors, this turns the output and you start to move.  As the pump reaches full swing the motors will start to swing back to restrict flow through the motor, this puts resistance on the ring gear and makes more power start to take the path of the sun gear instead.  This continues until the motors reach 0* in which the ring gear will be stopped and the power is 100% mechanically transmitted to the output.  For reverse they simply swing the pump the opposite direction which makes for a very seamless and smooth movement but the tradeoff is poor efficiency in reverse.   If you ever see a Vario you will notice how small it is, that is because there are no shock loads from shifting or direction changes.  Another downside to this transmission is noise, Fendt mounted it to help reduce a lot of it but you can still hear some of the whine. THe whine is evident in Deere and CNH tractors as well.

Efficiency was mentioned as being "poor" with CVT's due to the hydro drive portion.  Hydros are not always efficient, but CVT's themselves take a different approach to gain efficiency. The measurements confirmed by DLG of the total system efficiency with a Fendt were between 80-85% from 3-30kph in low range and similar for high range from 4-40kph. That is the efficiency from engine to axle. I need to find some numbers on what a powershift actually runs.

The range box on the Fendt is simply synchronized with no clutches. This is why its best to just shift it when you get to the field. It can shift on the fly but needs minimal loads on it to do so.  Failures in the range box from improper shifting have been the cause of many CVT failures. The range simply increases your efficiency when at lower speed and higher loads. It is not required to achieve full speed.

Claas, Steyr and ZF were major players in the CVT game early on as well. Deere initially used ZF and still does today in some models, but also designed their own Autopowr later on. CNH bought Steyr and now use their design in their tractors as well. Claas actually abandoned theirs for awhile and used ZF CVT's in their tractors but have since put more effort into their own CVT and have released it in some of their models.  Most brands operate similar to the Fendt just with a more limited range in the actual power split unit, thus needing additional ranges to cover the entire speed range.  If you are operating near the more mechanical end of the PSD in the range you are in they can be very efficient. The downside is they are large and not as smooth.

The Fendt Vario is truely a mechanically controlled transmission actually. This allows limp home providing the engine will run. All the computer does is move the mechanical bar to change the position of the motors/pump.  When something fails there is a rod you use to manually swing them.  The Vario sits in its own oil as well which can be advantageous although the fill location is in the rear which can be confusing for many as the hydro fills are to the side or front of the cab. When loosing hydro fluid many will overfill the CVT instead. It's not idiot proof.   Replacement is a nice feature of the Fendt CVT. It can be replaced in two days easily. The module is not serviceable and is less than 20k. They are in stock at major warehouses. Replacement just involves cab removal, then there is an acess plate to remove the CVT module. No splitting or anything time consuming. Cab is designed to come off easily.  The MF variant is not as fast to do as they crammed all of the hydraulics on top of the transmission which takes more time to remove. 

CVT's main  efficiency comes from systems like Fendt's TMS, being able to select the proper amount of power and RPM needed to achieve the ground speed desired while having an infinate range of speeds allowed. If you sit at full power all day you may not notice it as much, but with varying loads you can. Fuel cost for work done (not hours) is the impressive number especially if you are stuck between gears.  This may not seem apparent to those planting corn or something, but go cut hay with an older powershift and the jumps between gears once you get above 12 on something like a Magnum or Funk are very annoying.


In the end, you shouldn't buy one brand over the other just because of their CVT/IVT. There are too many other factors to consider.