TRANS FAILSAFE PROG message at higher speeds only

[andy406]

hi guys, hope you can help me on this topic. I recently got the dreaded TRANS FAILSAFE PROG message. but i only get this if i am driving over 50mph,
arround town it drives perfectly, but as soon as i get on a open road and do 50-60mph it will go into TRANS FAILSAFE PROG.

thanks in advance if you can help at all


regards andy

[Steamyrotter]

You will need to see what codes are in there to tell properly...

Is it the 5 or 6 speed version??

Do you get it in manual mode?  If so what gear...

It could be an issue with slip in certain gears which the ECU sees a speed difference it wasn't expecting, or torque convertor lock up clutch not engaging properly...(can you feel it locking up?)

Or it could be as simple as low fluid level or requiring a filter change...

Long distance diagnosis is hard.
Go to a reputable indy / gearbox place and get the codes read then go from there..
also, as i keep harping on about it,  you need to know what the fluid pressure is doing to be able to know what's going on...

[Spartanx5]

Silly question how do u monitor the fluid pressure? Only want to know because I have had this trans fail safe message for 2 months now, I have spent £3500 trying to fix it and got nowhere

[Steamyrotter]

There should be a tapping on the side of the gearbox for a pressure gauge.
(There is on the GM one, and is M10 Fine thread)

Not sure where or what it is on teh ZF but you should be able to google it, r get an exploded diagram for it..

I have a pressure transmitter permenantly fitted to mine and linked to an LCD matrix display via a PIC microcontroller.
It displays Gearbox pressure and both battery voltages.

It is really the only way you can tell what is actually happening in there
Couple it with the drive current for the pressure regulator solenoid (Measured through something like INPA)
you can tell what's up.

Last Trans Fail Safe I had showed loss of pressure which transpired to be a split cooler hose.
Showed up as loss of pressure on my display so parked it and got it uplifted home.

[Spartanx5]

Cheers for that info chap, I have it booked into bmw Peterborough Tuesday for a code read, I love the idea of being able to monitor pressures as I drive. I am very interested in sorting that out I will bug you for more info on how I do that when the main stealer gives me my car back after Tuesday

[Steamyrotter]

No Prob.
I'll draw up a little diagram and post it on here as I am sure others may be interested.
Will try to get a photo up as well to show the bits n bobs..

[Steamyrotter]

Spartan

Please see here:-

http://xdrivers.co.uk/forum/index.php?t ... 36.new#new

regards

[andy406]

sorry for the late reply to your message, I have been away on my holidays.
it is the 5 gear model  when I do drive it in manual in 5th gear it still goes in to trans failsafe mode, but if I leave in in 4th all is ok, kinda strange 
im not sure what you mean by lock up tho ?

hope you can help

kind regards andy

[X5Sport]

Lock up is where the drive effectively goes straight through rather than losing energy in the torque converter.  The TC is 'locked' to act similarly to a conventional clutch.  It uses a 'lock up clutch' at that point as long as the engine rpm is in the right range for that gear.

Richard

[Steamyrotter]

As Richard said..

According to the 'Manual' the lock up clutch will engage in 4th and 5th only.
and then after a certain speed and if torque demand is low.

What you will see (and more likey hear) is the engine revs drop slightly as it engages. you may feel a slight judder depending on the state of the torque convertor, but that is not normal.
When you lightly accelerate the engine speed shouldnt 'race away' as it is locked to the input shaft of the gearbox.
the biggest visible sign is the consumption meter drops but engine revs don't rise... if you see what i mean..

It is sounding to me that it could be a solenoid issue, or a clutch pack slipping. Having said that there are only 3 shift solenoids in the 5spd and the combination of those select all gears.
I need to look at the truth table for them to see what is engaged at that time.

There are 9 clutch packs in the box and the different selection of them cause the ravenaux (planetary) gears to effectively give you the required response...

If you search for my posts there is a link to the rebuild manual which has a good cutaway drawing of the box as well as the usual exploded diagrams (or mormal for the gearbox diagrams in my case!)
the EGS should store the failt if ther is one. most likely is slip in 5th.

There is also a know weakness with the valve bodies on these where they wear slightly and let fluid go whee it shouldn't. These can be sleeved but requires the bottom end of the gearbox to be stripped (box can be left in the car)

When i had my refurbed it cost just shy of £350 with one valve replaced and fully tested with 12 month warranty.

All the above just goes to show what a sad sod i am that i have researhed (and remembered) all that..