BMW M5 Forum and M6 Forums banner

61 - 74 of 74 Posts

·
Registered
Joined
·
708 Posts
Ok I didn’t understand the point of running the car on a lift to see what your max speed was. I still don’t see how that helps you diagnose whatever issue you might have. How does 330kph tell you anything about the ECU being stock? 7th is an overdrive gear so any top speed would not be in 7th. You have almost zero inertial load on the car, and zero aerodynamic or rolling friction loads. So I wouldn’t be surprised that you could see 360 kph in 6th, but this is a huge time waste and frankly dangerous.

That’s what I thought you did and why I consider it non-sense for troubleshooting 1/R gear engagement issues, but you’re free to do whatever you wish.

I have my extra trans stored away on a pallet rack, lots of effort to get to it. it seems you have found something wrong, so you should just repair that and see if it solves the problem.
 

·
Registered
Joined
·
95 Posts
Discussion Starter #62
Thank you for the reply, yeah no point of top speed , the main reason was to check the transmission is shifting normally and what gear it shifts and if the engine stall or get into safe mode, and if the someone played and got access to the engine ECU, and yeah it is dangerous, I don't have a history of the car so I trying to gather as much info as I could to understand what has happened to this car since or before it got the trouble it has now. .
I would fix the piston finding and test the car. I just need to research more on the installation of the slave cylinder.
Also I need to remove the pump motor to see why it stopped working since last time, possibly got overheated.
 

·
Registered
Joined
·
708 Posts
I read this thread again, and it seems to me that the PO bought an extra actuator block with the gear sensor strip. He likely did so because he tried to do a repair on the existing one and the issues remained. I’m thinking this is my situation since I did unsolder and replace the wires and repott the junction. That was a major PITA and very likely it’s not working correctly now for me. With yours, the frayed sensor is likely toast but it has to stay with that actuator block. The replacement one also has to stay with that block. The 1/R or whatever mis-matches are likely caused by swapping gear strip sensors with different actuators blocks (unclear if that’s what you did, but a reasonable move if you did). I did elude to that earlier here and mentioned that in the post on my thread, those sensors are married to the actuator blocks, which is why BMW doesn’t sell them separately.

So once you get your new motor, replace the actuator block that was in the trunk along with the correct sensor strip, bleed, then hope that you can do your adaptations.
 

·
Registered
Joined
·
95 Posts
Discussion Starter #64 (Edited)
I don't think he did change the wiring strip.
The scenario as I see it like this:
He got SMG failure ok, tried to troubleshoot couldn't figure it out,>dropped the box>removed the actuator block to repair the wiring harness and inspect the shifting fork> did the another huge mistake (not aligning the piston)>put everything back together>SMG still malfunctioning (can't even start the car)> remove M4 40 pin connector from SMG ECU to start the car to sell it at least with engine running (was in a limp mode though) with malfunctioned SMG>sold the car to a noob> the noob taken the car in every possible European cars' shop, couldn't figure it out>after 3 weeks the noob decided to sell the car again >I bought the car exactly in this state(SMG failure+M4 plug 40 pin unplugged for the engine to start for selling purpose, engine start in limp mode, shifter locked) (WITH BARLEY NO OIL IN THE SMG RESERVOIR).< the real main cause that if my scenario is true.
I started troubleshooting i can hear the pump but with 3 psi pressure, I have never thought there is no oil. My head followed basic hydraulic check the oil level, and sure enough I added 0.8L or more. Got enough pressure, started the adaptations, clutch bleeding passed, block failed, then passed eventually. Then I stumbled with the transmission-teach because the other HUGE MISTAKE, wrong block installation on R/1st piston.
What support my Scenario regarding the main cause of the failure was the low oil level is the PO's (who is not the original owner by the way) technician did think of oil problem but they dont know there is a separate oil system for the SMG, what they did is changing the transmission oil, because before I drop the transmission I drained the transmission oil to look for metal or any particles would indicate a broken gear for example, but what i found is brand new green differential oil !!!( I am glad they couldn't drive 1 inch with that oil in the box).
This car was sold because of a mistake being with people who are no capable to have it. Another thing it is very rare to have an expert repair shop around here for this type of cars and if there is any, they would charge a lot and I dont think a car this age and not maintained well would even visits them.
 

·
Registered
Joined
·
708 Posts
I removed the actuator block and tired to move the rods by hand. Basically I can’t get them engaged in gear by my thumbs with like 50 lbs of force. The whole trans starts to roll since it’s on the trans jack or the trans itself starts to slide a long the platform of the trans jack. I recall reading that the hydraulics generate up to 500 lbs of force to be able to shift the gears which makes sense. There’s significant effort on a “more conventional“ manual gearbox also which is why there’s the lever arm that has like a 10:1 advantage.
 

·
Registered
Joined
·
95 Posts
Discussion Starter #66
Mine was on the floor, I pull the rods with four fingers toward me and resist pulling the transmission with my feet, then pushing back to neutral is easy then switch to the opposite position to engage the other gear on the same rod then move to the next one. Then ones on the sides (R/1st and 2/4) relatively harder due to the side wall of the box, though R/1st is worse than 2/4. Then I move on to the ones in the center.
Wished If you could have been able to try that, I would have been relieved till I get the motor. I would say R/1st is something between 25%-35% harder.
 

·
Registered
Joined
·
708 Posts
I didn’t realize how hard they were to move but I can only get my 2 thumbs against the surface. I could push harder then I can pull, but pushing just moves the trans or the whole jack. Pulling I can’t generate that much force but at least my body can support the trans from moving abit. I don’t think I’d be able to observe a 25-35% difference if I could. All this makes sense on why the hydraulics need to generate 60+ bar of pressure to operate the box and clutch.
 

·
Registered
Joined
·
95 Posts
Discussion Starter #68
It is not necessary to measure the force differences, any differences will be sufficient to me. Also while you are there check for longitudinal clearance for each shift rod in it's neutral position for each side. I am not sure what does that mean but I have seen examples for failure to shift in certain gears, may be for worn out synchro's?.
 

·
Registered
Joined
·
708 Posts
I bolted the actuator back up after trying this for abit. Maybe I have weak baby thumbs. I can get some slight initial travel like 1-3 mm but it springs back or the whole trans starts moving. I then cleaned up the area and resealed it with locitite 518. That tube style dispenser is a PITA. It was a 50ml tube but I’m not sure there was really 50ml in there, it’s barely enough to run a thin bead around the perimeter. You can probably just use any RTV gasket sealant, this stuff is not RTV.
 

·
Registered
Joined
·
708 Posts
You seemed to have pressure issues, That can cause failure to engage and based on the sounds I can definitely hear and feel the differences when the pressure is at standard or when it is at max (during Adaptations). The synchros are supposed to be made of carbon fiber, but that says nothing about longevity. It doesn’t seem the gearbox itself fails based on the limited info we have on this board.
 

·
Registered
Joined
·
95 Posts
Discussion Starter #71
Pump pressure was fine, accumulator test passed, if it was pressure it would have failed other shift rod, the transmission only failed to engage R and 1st gear. you can hear the pump is having a resistance and that what overheated the motor and eventually died after almost 2 weeks of abusing, usually when I try to command those 2 gears the test stop after short trials, but the night before the motor give up, for some reason the engaging trial extended for a quite sometime and didn't cut, I was desperate and I kept it tries it's best, I should have stopped it, but I thought it is designed to do that or the system would stop it, it was obvious that it exceeded the normal engaging trial time. Notice that the gears that failed are on the same shift rod and both of them failed, which indicate that there is high resistance down there. I have never seen the letter R on the display during all the testing with different configuration i have used, nor even flashing on the dash, I only seen 1st flashing when it is commanded only.
 

·
Registered
Joined
·
708 Posts
The pump will shut off at 85 bar if you are allowing the system to trigger it. Otherwise the diagram says there is a pressure relief valve. The way to 100% manually trigger the pump is to disconnect the big 2 pin wire connector to the motor and power that directly via 12v, which I've done before but that was to test the motor after cleaning the housing from all the carbon dust. Not sure if you tried to clean out and inspect your current motor, it is very simple. Again some people here have talked about it but no real step by step directions, I can see why though it's pretty simple. open up the two ends, remove the commutator shaft, see if the brushes are intact or worn down. The whole thing will have a ton of black carbon dust, so wear gloves. Before you open it up, just make sure you mark the aluminum end caps indexed to the steel body with paint marks or scratches since any solvent you use to clean the stuff will dissolve away a sharpie or light paint mark. When you reassemble just hook up the pigtail manually to 12V and see if it spins.

1 and R use the same exact gear set, they are the same ratio, it's just that in R there is an idler gear that is engaged that allows the output shaft to then spin in the opposite direction, thus giving us R.

Are you going to just replace the gearbox or try to fix it? Seems cheaper to get another gearbox that already has the hydraulics all stripped off. I have the guts to an SMG gearbox, but that's something that most people won't get into (tearing down a gearbox and replacing stuff) there is no documentation on how to do that AFAIK.

I'd be less concern about what you see on the display and more concerned about whether the box is in gear. Other than the sound, the way to find that out is let it shift and then spin the input shaft by hand and look at the tailshaft. Once the mechanical state is validated, then you can determine better what is going on with the controls system. It's generally the sensors and wiring that become flaky and unreliable.
 

·
Registered
Joined
·
95 Posts
Discussion Starter #73
The motor is burned I already confirmed that, I applied direct 12V it didn't move, that was the time when i decided to drop the transmission, I tried every possible way to make it shift, also used that time to learn more about the theory of operation to set a plan on what I am going to do when I drop it. The main reason for dropping the transmission is to test the gears manually and check if they are possible to engage each one and to check if the output shaft turn according to that
941860
. I was excited when found that the travel piston for shift rod R/1st is not correctly installed because I hoped that this the reason of the malfunction, but to be honest I still not confident if that would be the cause. In TIS there is a big note to position all travel piston in the correct position before installing the shifting block on the transmission. That was one of the steps I included in my plan to check before dropping the box.
The higher resistance to engage R and 1st gear could be because their larger size gear and synchro. ( I wish this is the reason) if not anything else internally.
I have no intention to disassemble or repair the gearbox to fix the malfunction(zero experience, tools, and parts), I would find another gearbox.
My plan is to correct the position of R/1st shift rod travel piston, replace the pump motor service and install the transmission temporary and test.
 
61 - 74 of 74 Posts
Top