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Author Topic: 2003 WJ 2.7 CRD Transmission Not Engaging Gears in 4 All Time  (Read 3018 times)

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matt81

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2003 WJ 2.7 CRD Transmission Not Engaging Gears in 4 All Time
« on: November 02, 2017, 11:18:51 PM »

Hi,

I'm having a bit of a headache with the transmission on my 2003 WJ CRD and haven't managed to find any post which seem to describe the same problem. The car's done about 144,000 miles and the gearbox hasn't ever been serviced and the transfer case fluid should have been changed about 15,000 miles ago or even longer if it hadn't been changed for a while before I bought the car.

The first sign of a problem I had was that after a longish drive (over about 70k miles) the engine warning light would come on and put the car into limp mode. The light would only appear intermittently for a few days and then wouldn't come on again until I did another long drive. I checked the fault codes and got P0702 and P0836. I read that this usually meant there was an issue with the transfer case position sensor and decided to take the car into the Jeep main dealer to investigate as I wanted to get the gearbox and transfer case serviced too.

The Jeep garage plugged in their diagnostics, but couldn't get it to connect to the car properly as they needed a different diagnostic machine for a car of this age. They checked the gearbox fluid level too and said it was a little low, but the colour of the oil was ok and there was no indication of any mechanical faults.

When I went to drive away from the garage though I found that I now had no gears at all. If I moved the shifter into drive or reverse the gear wouldn't engage at all and if I revved the engine it would only go to maximum of 1,000 RPM, as if it was being limited. The mechanic came and had a look and found that if you put the shifter into gear immediately after starting the engine the gear would engage, but then if you shifted from drive into park or reverse none of the gears would work and you had to turn the engine of and on again. Once moving though the gearbox works fine as long as you don't take it out of drive. You can engage 4Lo though and both reverse and drive work fine, but then if you switch back to 4 All Time the gears don't engage again.

They got the right diagnostics tool the next time I went in, but it didn't really tell them much. Apparently the shifter module PCB seems fine as it's sending the correct signals though about the gear selected, so they think it might be the transmission control module that's faulty, which is about £750 to replace and they can't even be sure that will solve the problem.

Has anyone else had similar transmission problems on a CRD WJ? I've read lots of posts on boards about the shifter module PCB failing and the transfer case position sensor casing faults, but nothing really about the transmission control module failing.

Would a problem with the transfer case itself or the sensor caused 4 All Time to stop working, but allow 4Lo to work still? I've tried reading upon how the Quadra Trac 2 system works, but can't see an obvious reason for 4 All Time not working when 4 Lo does.

Matt

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carljh

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Re: 2003 WJ 2.7 CRD Transmission Not Engaging Gears in 4 All Time
« Reply #1 on: November 03, 2017, 02:39:31 PM »

At that mileage even tho its supposed to be a sealed for life gearbox I would do a filter and fluid change and see if it helps.
The problem is the dealership probably don't have a mechanic who remembers working on something made 15 years ago, so are just guessing whats wrong.
You could try going to your local Merc dealership and asking them for an idea what could be wrong as its their engine and transmission in the car.
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daggie

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Re: 2003 WJ 2.7 CRD Transmission Not Engaging Gears in 4 All Time
« Reply #2 on: November 03, 2017, 07:30:11 PM »

we had this on my parents 2.7.
I re-wired the transfecase switch, from the ecu, it been fine for 2yrs or more
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matt81

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Re: 2003 WJ 2.7 CRD Transmission Not Engaging Gears in 4 All Time
« Reply #3 on: November 06, 2017, 03:33:45 PM »

Thanks for the replies.

I removed the centre console today to have a bit of a poke around myself and noticed oil on one of the cables going into the TCM. I have read that the gearbox plug adapters can leak over time and the oil travels up the wiring loom and into the TCM, which causes various issues. The actual connectors on the TCM look fine, but I wonder if the connector that plugs into it is causing a problem as there was quite a bit of oil over the wires where they go into the connection plug.

Jeep are going to try changing the TCM first to see if that solves it, but I've also asked them to do a full gearbox and transfer case service and order in a transfer case position sensor so wecan try changing that if the TCM isn't the cause of the fault.

I'm taking it into them this week so will post an update afterwards.

Matt
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Mike Pavelin

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Re: 2003 WJ 2.7 CRD Transmission Not Engaging Gears in 4 All Time
« Reply #4 on: November 07, 2017, 08:23:13 AM »

If there's oil in the wiring harness, it's usually caused by the electrical 'plate' in the transmission that includes the connector the harness plugs into weeping oil. A very common Mercedes-Benz problem inherited by Jeep in the 2.7 WG.
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