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Intermittent Transmission fault

2919 Views 6 Replies 2 Participants Last post by  RRPhil
Hi all, I have been following this forum for a while but this is my first post. I was lucky enough to get a 2002 L322 from a family member just over a year ago. It is in fantastic condition and has only done 60k miles or so. (Two mechanics who have seen it for various minor things have wanted to buy it for themselves because it is in such good nick). I use it for towing horses every other weekend or so and it has done wonderfully for me so far. Whilst I was towing a couple months back I got a transmission overheat message. Pulled over and waited to cool down and then finished my journey. Took the car to my mechanic the next day who found that the transmission cooler was leaking. Fluid was burned, so we replaced the cooler and the fluid. Have been towing again since and the car has worked great, no more overheat notifications. Prior to changing the fluid I had also noticed a slight rumble under the car at about 40-50mph from time to time but that went away as well after the fluid change (I understand this can sometimes be a torque converter symptom).

In the past week or so I have had the trans go into failsafe mode. Each time it is when I am leaving work. I stop at the parking barrier which is on a steep uphill. When I move off the car initially moves forward for a moment but then seems to slip and go into failsafe mode. The only time it has happened is when I'm on this steep uphill. I am wondering what could be causing this. Could it be simply that the fluid needs topping up? That's what I'm hoping but I don't know enough about transmissions to know whether this could be something more serious.

I have read several posts on the forum to try and work it out but I can't find a thread that answers it, so apologies if this has been answered before and I have missed it. I don't have much experience with mechanics/working on cars but am fairly practical and willing to give things a go.
Many thanks in advance for any advice.
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Hi Alex, and welcome to the forum :D.

Land Rover fitted five different transmissions to the L322, and each has its own faults and peculiarities, so it’s important to let us know which model you have (i.e. 4.4 V8 petrol or a 3.0 TD6 diesel).

Hi Phil, it is the 4.4 V8 petrol, one of the early BMW engines I believe. Thanks,
You have the ZF 5HP24 transmission. So your transmission fluid will still be cold when it goes into failsafe? Your failure symptoms aren’t the usual ones that you see for this transmission. Certainly it’s worth checking that the fluid level is correct :

  • Vehicle must be level
  • Engine must be running
  • Fluid must be at 40°C
  • Only use Mobil ATF LT71141 fluid
  • Fill until a thin thread of fluid pours from the filler/level plug

but you really need to get the diagnostic codes read as the failsafe code will be stored in the controller, which will tell us the cause. Note that the transmission fault codes are Land Rover specific so you must use a piece of diagnostics kit capable of reading these codes. A standard OBD code reader will not work.

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Thank you Phil for the above information. I know my mechanic has some more of the fluid from when he changed it last time and I am sure it is the right stuff because we had a conversation about it and I remember how expensive it was. I have to go pick up my other halfs car so will top up the fluid whilst I'm there. I have a code reader so was able to pull the codes. The fault showing for the gearbox is P0730 which is showing as incorrect gear ratio. Does that help?
Thanks again for taking the time to help!
And sorry yes, car is still cold when the fault is happening.
Unfortunately, P0730 is a generic “the speeds measured by the two speed sensors don’t tie up” error, though it’s often accompanied by P0731, 2, 3, 4 or 5 - depending upon which gear is slipping (1[SUP]st[/SUP] to 5[SUP]th[/SUP] respectively). Because the issue happens when the fluid is cold, and the vehicle is on a steep slope, it’s quite possible that low fluid level is the culprit.

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