1st X5, 1st problem - Gearbox slipping

[stuartwaite]

I have recently purchased my 1st BMW X5 4.4i Sport (E53) with the 5 Speed ZF5HP24 transmission. It has developed a fault similar to those others have documented on this and other forums. The primary symptom is loosing drive in 1st gear if anything other than light throttle is applied. It goes into neutral then either bangs into 2nd or throws a TRANS FAILURE error and goes into limp mode. The box seems to shift sweet enough between all ratios once on the move with the exeption of occasional hard downshift between 3rd and 2nd whilst braking downhill. I have pulled the codes from the EGS and get a 31/A1 - Symptom gear check.
The poblem appears worse when the box is cold

In your experience is this likely to be a sensor error or a physical fault in the heart of the beast?


Thanks in advance
Stuart Waite
Ludlow
Shropshire

[RRPhil]

One thing you could try: Is the problem still there if you select 1st gear in manual mode before you accelerate away from rest? This would identify if you have an issue with the one-way clutch. Your transmission will engage the F brake in manual mode which bypasses the OWC.





Phil

[stuartwaite]

Hi RRPhil
First let me say how massively impressed I am with your posts on here and the rover forums. The depth of your knowledge is fantastic and your clarity of thought and logical approach to fault diagnosis is a rare and precious skill.
I am both honoured and delighted that you have replied to my plea for help

I have tried sport mode and manual and it is better but not perfect. Starting in manual 1st and 2nd still causes a false nuetral if giving it too much gass. The best is manual 3rd but then it struggles with slow takeoff particularly on an incline with the torque converter working very hard. If it was TC slipping causing the mismatch between input and output speeds I would have expected it to show up here too! When taking off in Auto you can feel when it is about to happen - you can feel a slight reduction in acceleration and the revs rise rapidly. If you lift off at this point it engages 2nd and then you can gradually feed the power in and proceed as normal. If you ignore the telltale signs and keep your right foot down then you either get a box of neutrals or it slams into 2nd with a bang. 50% of the time I then get a TRANS FAILURE error which can be cleared by stopping, cycling the ignition, restarting and then starting again VERY SLOWLY. Because I am experimenting with unusual gear selections it seems the software can get easily confused and it has suddenly swapped to 3rd, 5th, 1st and then TRANS FAILURE all when doing less than 20mph!
Is there any tests I can do without removing the gearbox?
I thank you in advance for your precious time
Regards
Stuart Waite

[RRPhil]

I must admit, what you’ve described doesn’t sound like any of the ‘usual’ 5HP24 issues.

Your statement that the problem appears worse when cold immediately flags low fluid level as a possible cause. Have you noticed any leaks at all? May be worth checking the level - this is the procedure:



In case it needs it, only use Mobil ATF LT71141 for topping up (ZF Lifeguard Fluid 5 and Pentosin ATF 1 are difficult/expensive to source here in the UK).



Because there are so many potential faults (mechanical, hydraulic, electrical, electronic) we’re heavily reliant on the diagnostics to give us a clue as to what’s going on inside the transmission and transmission-specific DTCs are usually in the format ‘P0735’. What piece of kit are you using to read the codes? Is it just a generic code reader?

Phil

[stuartwaite]

Hi Phil
The car is loosing oil as fast as the Torrey Canyon but is appears to be engine oil not ATF. I will check the fluid levels following your kind instructions.
I have a generic OBDII reader but that would only pick up the engine DME codes. I acquired a BMW Scanner 1.4.0 with software but the codes are in HEX or Decimal.
I have also downloaded all the BMW diagnostic and coding software INPA DIS EDIABAS from the BMW Coders forum but don't have a suitable interface cable yet and it looks a bit scary.
I'll report back when I've been underneath
Thanks again for your help
Regards
Stuart

[stuartwaite]

Quick status update - no oil from filler plug in gearbox even when hot
I think that may explain a lot!
Have ordered some LT71141 a delivery pump and an IR temp monitor so will try to top it up as soon as it all arives.
If it fixes it I will just have to find and repair the source of the fluid loss. I will also do a full flush and filter change for good measure.
I'll report back ASAP
Regards
Stuart

[stuartwaite]

Hi Phil
Well spotted :-) I have introduced 2 litres of clean oil into the system but still no oil from filler plug even at 50 deg C. The gear shifts are perfect and all error codes have gone. Oil was overflowing at 35 deg C with the engine off but nothing with the engine running and the tranmission in park. It just shows that you have to follow the oil level check procedure to the letter. With regard to the faults I can only assume that the low oil level was causing the pump to suck air. This condition was worse under heavy acceleration or on a hill start or when turning out of a junction where the sump oil was forced either to the rear or the side of the sump. As soon as air reached the pump the pressure would drop in which ever circuit was active causing immediate release of that gear followed by lots of software alarms. It all makes perfect sense. I will top off the system when more oil arrives. In the meantime I just have to diagnose where the fluid is escaping from. The box itself is dry with no obvious sign of leakage however the alluminium plate under the engine is wet with fresh oil with the occasional drip from the anti-rolll bar. My bet is the front seal unless there is a leak in the cooler circuit. I will report back after further investigation.
Well done again RRPhil for a spot on diagnosis from the described symptoms.
Thanks from a very relieved X5 newbie
Stuart