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.
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.
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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
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.
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.
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.
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?
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.
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?
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.
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.
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.
In my opinion it is stuck in 2nd gear when I select 1st or 2and position on the shifter.
It sounds like you have a stuck spool in the control valve. But you need to check shifter signals and control module first.
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.
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?
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?
Mike, to check shifter dismantle cover of steering column. There should be a plug with signals from shifter. Signals from TCU is basically the plug at control valve. Internal crack is very very unlikely. Never heard about this. Possibly one of these steel plates fallen out. However these are only fitted in bottom spools for KV, KR, K4. No blockage of t/m to output possible. Mixing up spool 2 and 4 is not possible. Blowholes in cast unlikely. Rather broken gasket.
Thanks Bigbert. I'll give testing the output from shifter and control module a try. When I unplug the electrical plug from the control valve will the control module detect that and shut down the circuit?
Hi Mike, the "old" EST 25 (TCU box) did not shut down outputs, as far as I recall. ). Else remove sheet metall cover at control valve and check at solenoids. Box could be located under cover behind seat, again, as far as I recall.
Hi. The tcu is behind the drivers seat and relays on the right hand side under the instrument cover. I have had the metal cover off the solenoid on the control valve but when you unclip even 1 of the wires from a solenoid there is no signal from the tcu. I think it shuts the circuit off when it detects a loss of connection. Starting the machine with that cover off is a non starter as oil spews out everywhere. The wires onto the solenoid have insulating plastic clips which prevent testing the solenoid in circuit. The tcu has a special connector which has to be completely removed to expose anything.
Hmm..it is long time ago I worked with EST 25. The TCU should power the solenoids also without engine running. Anyway, please focus on pressure measurements. Neither TCU nor control valve hardware would allow blockage of t/m. And the baby was working before repair, isn't it? I'm still convinced we have an issue in or around control valve.
The TCU is behind the seat under the cover.
Morning. I have done pressure tests and will attempt to post the results .
Hi Mike, you have an issue either on K1 and K2 clutch or M2 spool or gasket around M2 spool. Are you able to block the hoses to the clutches or the plugs to the hoses? With a ball and a nut. So you'd be able to find out were you have the troublemaker, clutches or hydraulic block. Pressures of clutches need to be around 16 +2 bar in all gears. Still strange to me why t/m is locking up in 3rd and 4th. If you'd keep K1, K2, KV, KR hoses blocked, only connect K4 and K3, what would happen? Still locked? Going back the entire story: What was the reason to clean the control valve before you ran into the troubles?
Hi Bigbert, The reason I dismantled the control valve in the beginning was because previously when pushing a load in 1st gear the machine would jump/hop rapidly when revving up to get power. On dismantling the control valve I found broken and cracked gaskets and a small piece of metal about 6mm long (slightly curved) which looked like it came from a filter or bearing cage. I am doing a circuit isolation test on k1 and k2, ie block off the hoses to the trans shafts to see if the pressure comes up. I will also block k1 k2 kv kr and see if the trans still locks in 3rd or 4th. The manual does suggest that if the pressure comes up when doing the circuit isolation test that indicates worn seals on the shafts. But doesn't explain the trans lock up in 3rd and 4th. Mike
Hi Bigbert. Posted above are some findings from circuit isolation test. Bit confusing. Dont know what to make of it. Does this reveal any clues to you?
I have just blocked (circuit isolation) k1,k2, kv and kr hoses and found that 3rd and 4th are not locking up.
Hi Mike, the pressures from control valve look nice. So, bad news, there is a mechnaical issue in the clutches. Does oil smell somehow burnt? Guess, KV; KR, K3 and K4 are fine. There is some leakage or blockage or extreme dragging in K2 (or K1), I assume. Already your first picture showed low oil pressure in 1st and 2nd, FWD and REV. I'm afraid the transmission has to come out of the machine. Will you do the repair or give it to a workshop? Could provide a repair manual via email. regards Bigbert
Hi Bigbert. I will check the condition of the oil but as far as I know not smelling burnt. I am making preparations to remove the engine and transmission, I will do it myself. I would much appreciate it if you could provide a repair manual via email as I am not sure how thourough the one I have is. My email address is [email protected] Thanks for your advice. I have had the fear that the transmission would have to come out all along. Do you have any helpful tips to make the task easier. Should I remove the engine and transmission together or separately? Thanks Mike