Case 621 loader

I’ve just bought a 621 loader. According to the guy I purchased it from, he just had the transmission rebuilt but it doesn’t have fourth gear. He told me it was a solenoid but I’ve done an ohm’s test on all of them and they seem to be working. My next step is the check the pressures. Anyone have any thoughts

Hi Jeeper,

which kind of transmission is fitted?
ZF 4 WG150 or 4 WG 180 or something else?
Type plate should be located around bottom of trasmission housing.

Yes, early 621's ran a Clark Transmission - so we do need to know what you have fitted to give specific help.
A machine serial number might also be of assistance.

ZF. Serial number is after the cut off number. I will post ASAP.

I also noticed when I shift from first to second, no change in gear. From second to third it shifts I’m thinking into third because of the high gear. From third to fourth nothing. No shift and as if you put it in neutral. In reverse it goes into first, shift to second and no change. Shift to third and it shifts. To fourth, stays in the same gear as third. I assume reverse only works in first and second as the writing on the shifter states?

So I'd rather assume the issue is from signals from gear selector.
Guess, the loader runs without TCU (electroic box), just a gear selector firing solenoids directly.
4 solenoid control valve?
Is AD1 (B1) wire broken? And transmission only skips between 2 and 3?
Clear in German, blurry in English.
Sorry.

Jeeper welcome to HEF, as you ask for thoughts, here is mine with the disclaimer I am not experienced on a 621 with ZF transmission.

From the problem description it sounds one of the shift rails in the transmission is not moving. Specifically the transmission is stuck in the 1/3 position, so you can select 1st or 3rd, but the other shift rail that selects 2/4 is not moving.

While you have checked solenoids ohms, that does not prove the wiring harness is powering the shift solenoids, nor does it prove that one of the solenoids is stuck physically.

If both solenoids are the same p/n, then I would suggest swapping them and see if the problem moves. (move the entire solenoid valve assemblies, not just unscrewing/moving the solenoid coils) If problem moves, you probably got a physically stuck solenoid valve.

If no change, then confirm that the wiring harness is good between the transmission controller and the solenoids and the controller is electrically commanding both solenoids.

If electrically everything is ok, then start digging into why the transmission shift rail is not moving. Others on this forum have much more knowledge of 621s and ZF transmissions than I do, and can hopefully advise further.

You need to test your shifter contact switches, I'm assuming you have the Clark shifter. Also sense you have the ZF transmission check the speed solenoids in the transmission. And oh by the way you will not have 4th gear in reverse.