621B trans problem.

[Mike Fryer]

Hi. I have a 621B. In 1st and 2nd gear the machine will move forward and backwards. But in 3rd and 4th the transmission actually locks up and the machine stops moving immediately as if you have applied emergency brakes. I have switched around the m1 m2 m3 m4 and m5 solenoids and makes no difference. Would the declutch relay or brake system have anything to do with this? I realise that 3rd and 4th gear are on the same shaft in the transmission, could it be a mechanical issue on that shaft?
Any suggestions would be appreciated.

 

[Nige]

What that sounds like to me is that whichever of the transmission clutches is common to 1st and 2nd speed (low range clutch maybe.? not sure) is mechanically locked up for some reason. So then when it is required to disengage (i.e. when you select 3rd or 4th) there is then an additional clutch engaged where there shouldn't be and the whole shooting match locks up.

Note: I don't have any personal knowledge of your particular transmission.

 

[seatwarmer]

Please read this:
https://www.heavyequipmentforums.com/threads/help-case-621b-trans-problem.15344/

Are you related to General Mike Fryer SA Police Special Task Force Commander ?

 

[Bigbert]

Hi Mike,your findings do not look like the clutch cut off device. The clutch cut is usually active only in 1st and 2nd, disengages forward/reverse clutch KV/KR. 3rd gear is KV (upper shaft)/K3 (lower shaft), 4th gear is K4/K3, both lower shaft.
Are you able to check the pressures on control valve or simpler way, feel pressure on hoses from control valve to shafts?
Did someone modifications on hoses? Mixed up somehow?
Guess, the transmission is a 4WG180 or 200.
Could get you a manual via email.
regards
Bigbert

 

[Mike Fryer]

Please read this:
https://www.heavyequipmentforums.com/threads/help-case-621b-trans-problem.15344/

Are you related to General Mike Fryer SA Police Special Task Force Commander ?

Hi. As far as I know I am not related to the general. I have already read through the posts on the link you provided. Since this is 3rd and 4th gear I have a problem with I didnt find anything there to be relevant. Thanks all the same.

 

[Mike Fryer]

Hi Mike,your findings do not look like the clutch cut off device. The clutch cut is usually active only in 1st and 2nd, disengages forward/reverse clutch KV/KR. 3rd gear is KV (upper shaft)/K3 (lower shaft), 4th gear is K4/K3, both lower shaft.
Are you able to check the pressures on control valve or simpler way, feel pressure on hoses from control valve to shafts?
Did someone modifications on hoses? Mixed up somehow?
Guess, the transmission is a 4WG180 or 200.
Could get you a manual via email.
regards
Bigbert

Morning. I have changed some of the hoses from control valve to shafts and my first thought was that I had connected them back wrong. I have a service manual and have checked the routing 3 times. This 621B has a ZF 4WG-150/4 transmission. According to the manual top shaft is forward and 1st gear, middle shaft is reverse and 2nd gear and bottom shaft is 3rd and 4th gear.

I did have the control valve off because initially all gears were there but in 1st gear pushing a load the machine would jump rapidly when revving up to get full power. On removing the control valve i not only found two of the gaskets had tears and missing bits but i discovered a piece of metal about 5 -6mm long lodged in the M4 spool chamber. Looked like it may have come from the filter possibly. I flushed out the transmission and control valve, replaced all the gaskets and reassembled. This is when 3rd and 4th years stopped working. The problem i was having with 1st gear has gone. It was also at this time when 2 of the pipes from the control valve to the shafts started leaking. In disassembly and assembly of the control valve I followed the manual exactly. I'm starting to think (as nige suggested) that there is a problem on the 3/4 gear shaft, in that it is engaging both gears simultaneously. When I select 3rd or 4th gear the transmission literally locks up and machine skids to a halt.

 

[Mike Fryer]

Hi Mike,your findings do not look like the clutch cut off device. The clutch cut is usually active only in 1st and 2nd, disengages forward/reverse clutch KV/KR. 3rd gear is KV (upper shaft)/K3 (lower shaft), 4th gear is K4/K3, both lower shaft.
Are you able to check the pressures on control valve or simpler way, feel pressure on hoses from control valve to shafts?
Did someone modifications on hoses? Mixed up somehow?
Guess, the transmission is a 4WG180 or 200.
Could get you a manual via email.
regards
Bigbert

I have tried to do pressure checks on the control valve but the adaptors I have are too long and the space between the control valve and the chassis/brake pipes restricts this. Of course holding the pipes while someone engages the gears to feel for pressure is a possibility since I have a work pit. I will give that a try.

 

[Bigbert]

Hi Mike,

I'm still convinced you have an issue with mixed hoses. Or spool(s) fitted the wrong way.
To block the loader you need to have K1, K2 or K3 combined with each other. Only these clutches can block transmission towards output. KV, KR, K4 towards input, (but would allow free travel of output).
You have the manual?
The speeds of 1st and 2nd gear are allright? Also reverse? What about 3rd reverse?
The spools in control valve are fitted in correct direction? Usually no chance to pressurize two gear clutches (K1, K2, K3) the same time with bad solenoids or sticking spools.
Good luck
Bigbert

 

[Mike Fryer]

Hi Mike,

I'm still convinced you have an issue with mixed hoses. Or spool(s) fitted the wrong way.
To block the loader you need to have K1, K2 or K3 combined with each other. Only these clutches can block transmission towards output. KV, KR, K4 towards input, (but would allow free travel of output).
You have the manual?
The speeds of 1st and 2nd gear are allright? Also reverse? What about 3rd reverse?
The spools in control valve are fitted in correct direction? Usually no chance to pressurize two gear clutches (K1, K2, K3) the same time with bad solenoids or sticking spools.
Good luck
Bigbert

1) I have a 621B/721B manual. Part no. 7-60064.
2) just rechecked hoses and are routed according to service manual diagram.
3) I assembled the control valve as per service manual. The spools in the direction shown in the diagrams.
4) the operating speed and power of 1st and 2nd appear to be about the same (no different to each other) in forward and reverse.
5) 3rd gear in reverse or forward locks up transmission as does 4th gear.
6) this transmission has the auto shift control valve and M6 solenoid. Could that play a part in all this?

 

[Bigbert]

Mike,

please prepare a pipe to become able to measure pressures at the ports on control valve.
item 4) Looks like M2 spool doesn't move.
item 6) M6 is the "fastfill" or "reset" valve to guarantee full modulations in any shift case. So, I doubt, has an impact on issue.

 

[Mike Fryer]

Mike,

please prepare a pipe to become able to measure pressures at the ports on control valve.
item 4) Looks like M2 spool doesn't move.
item 6) M6 is the "fastfill" or "reset" valve to guarantee full modulations in any shift case. So, I doubt, has an impact on issue.

Hi. I will do this. Might take a while as this country is still in partial shut down. If you think of anything else please let me know. Many thanks.

 

[Coy Lancaster]

Hey Mike have you checked your speed sensor in the side of the transmission housing and also your converter speed sensor?
Also have you tested your shifter?

 

[Mike Fryer]

Hi coy, no I have not checked any of those. Could any of the sensors cause 3rd and 4th to lock up the transmission. In addition 1st and second seem to be the same ie both positions are selecting 1st gear.

 

[Coy Lancaster]

Does the machine actually lock up or does the transmission just quit pulling all of a sudden. The speed sensors send a signal to the transmission control module to let it know what gear can be selected.

 

[Mike Fryer]

When I select 1st and second in forward or reverse I get movement but there seems to be no difference in power or speed between the two of them. When I select 3rd or 4th the transmission actually locks up. If the machine is moving at the time I select 3 or 4 the machine violently and immediately stops.

 

[Mike Fryer]

In my opinion it is stuck in 2nd gear when I select 1st or 2and position on the shifter.

 

[Coy Lancaster]

It sounds like you have a stuck spool in the control valve. But you need to check shifter signals and control module first.

 

[Bigbert]

A sticking spool or bad solenoid or wrong shifter signal or wrong signal out of TCU would explain 2nd gear revs like 1st. Blockage t/m output in 3rd and 4th is not possible from hardware of control valve. You'd need swapped hoses or incorrect position of spool(s).
Check pressures on valve body and come back.

 

[Mike Fryer]

It sounds like you have a stuck spool in the control valve. But you need to check shifter signals and control module first.

Hi. Thanks for your input. I dont have the test module shown in the manual. Where/how is the best way to check for signal from shifter and control module?

 

[Mike Fryer]

A sticking spool or bad solenoid or wrong shifter signal or wrong signal out of TCU would explain 2nd gear revs like 1st. Blockage t/m output in 3rd and 4th is not possible from hardware of control valve. You'd need swapped hoses or incorrect position of spool(s).
Check pressures on valve body and come back.

Thanks Bigbert. I am looking for an elbow to enable me to connect my gauge to the control valve. If electrical testing doesn't reveal anything I will have to remove the control valve again and recheck spools solenoid etc.

I had a thought, could an internal crack in the control valve cause this type of behaviour?