FAQ Gearbox - shift unsynchronized gearbox correctly

[Joachim]

How do you shift a unsynchronized transmission, such as on older Zetor tractors? :think2:


Zetor Transmission diagrams in sectional view

With a little practice, shifting an unsynchronized gearbox is relatively easy:

Approach:

On the level without load, do not choose the lowest gear; with a 5-speed transmission you usually start with 4th gear, with a 4-speed transmission you use 3rd gear.

Upshift:
Using the example of 3rd to 4th gear:

1. Press the clutch, take out 3rd gear
2. Release clutch (gear lever in neutral)
3. Press the clutch, engage 4th gear
4. Let the clutch come back


Downshift:

1. Depress the clutch and take it out of gear
2. Release clutch (gear lever is in neutral)
3. briefly accelerate
4. Depress the clutch and select a lower gear
5. Release clutch

Downshifting is much more difficult than upshifting - but again it's just a matter of practice.

Note: On some Zetor models a partially synchronized transmission was installed, where the 2 highest gears in a group were each synchronized. E.g. with the UR1 series "2" (5211-7745T), such as the Zetor 5211 etc. Some Zetor models also have a gear brake, such as. 4911... and 5011 to 7745T, which makes shifting the unsynchronized gearbox easier, provided they are not worn and Go to:


View: https://youtu.be/_pD9R9Tqt8w

With synchronized transmission:

Go to: https://youtu.be/VI6nPhnHHcw



Why, on the other hand, are “synchronized” transmissions easier to shift?

Go to: https://youtu.be/o0WQh3VYLPM?t=18s[/SIZE ]

 

[Bert Zegers]

Some Zetor models also have a gear brake, such as. 4911... and 5011 to 7745T, which makes shifting the unsynchronized gearbox easier.

The way the clutch is used in a un-synchronized highway tractor ("truck") with gear brake is:

From a full stop:
You push the clutch all the way to the floor, and shift in gear.
Pushing the clutch all the way to the floor stops the gearbox input shaft.
Now the input and output shaft are both stopped.

While moving:
You push the clutch half way to change gears. Now the gearbox input and output shaft are both running.
Pushing the clutch all the way makes it almost impossible to change gears and it grinds the gears.
Synchronizing the gears is done by the driver through choosing the right gear, speed, rpm and by double clutching.

Experienced drivers use the clutch only when shifting in-gear from a stop and out-gear to stop. While driving the clutch is not needed if gear, speed, and rpm are chosen correctly.
I wonder if the same would work with a tractor on the road.

 

[Joachim]

Your last point, these are often the transmissions where the shift gate suffers the most because the drivers often shift gears quite quickly and the double H gate shifts improperly.
I wouldn't want to try that with my gearboxes.

The transmission brake is not installed on all types and is not the same on all models (with hydraulic clutches this is addressed and adjusted differently).
Experience has shown that the original rubber (mechanical clutch with transmission brake) is too hard to be able to use the transmission brake in a measured manner. So I made a different rubber for my tractors that was initially a little softer and then harder (progressive) and had good experiences with it.
For the hydraulic clutch, the original rubber works quite well.

But - the system is only as good as it is set up. And that's the biggest problem, because many people don't even know that this transmission brake exists, how it works and how to properly adjust it...

There is an entry in the resources on our sister site, which I will translate in a few days and make it available here in the forum.

 

[Renze]

Experienced drivers use the clutch only when shifting in-gear from a stop and out-gear to stop. While driving the clutch is not needed if gear, speed, and rpm are chosen correctly.
I wonder if the same would work with a tractor on the road.

That works with an unsynchronised UR2 when loaded. Empty, it looses speed too fast between 2nd and 3rd but loaded i only use the clutch to take off. The clutch pedal is quite heavy, and the gearbox lets you really "feel" without grinding. You just have to be sure that the claw couplings are fully engaged before you press the throttle down again.

Just synchronise the shafts with the throttle, using all gear splits (pull down hare to turtle when the gearstick is in neutral)

 

[EgilF]

The first Zetor we had with a partially synchronized transmission on the 2 highest gears (4 + 5) was a 1984 model 6045.

I think my 1976 model 5745 has a gear brake, but not shure if it works perfect, the rubber is old and hard. It would have been useful with a detailed description of how to adjust this gear brake.

I learned the technique of shifting an unsynchronized gearbox on a Ferguson 35, and after some years practiced shifting between the two highest gears (high 2nd and 3rd) without using the clutch, just the right rpm and medium throttle.

 

[Renze]

I think my 1976 model 5745 has a gear brake, but not shure if it works perfect, the rubber is old and hard. It would have been useful with a detailed description of how to adjust this gear brake.

Its just a steel latch pushed against 4th gear.

 

[Joachim]

New stuff:

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