gearbox problem?

hi i have just came back from a caravan holiday with my 4.4 03 lpg converted rangerover towing a large 4 wheel caravan 2 tonnes hardly new it was there my car went into 3rd gear lock arount 20 miles into journey would not change up did not get trans overheat message and had to drive 80 miles in 3rd gear kept her to 50 /3000 revs no rise in temp no funny noises just realy annoying and used more fuel after unhitching caravan transmission returned to normal changed gear no probs she seems to just do this when towing started when going uphill changing from 4th to 3rd up and down until trans lock anyone any ideas

If your ZF 5HP24 transmission controller had detected an internal fault it would normally failsafe to 4th gear and not 3rd (and also display the TRANS. FAILSAFE PROG message on the message centre), so that doesn’t sound like the issue.

If the transmission fluid is overheating the transmission ECU will inhibit upshifts, even if the fluid hasn’t exceeded the threshold necessary to trigger the overheat message. So that’s a possibility.

Another possibility - The transmission controller has a Hill Mode adaption which it automatically selects if the engine torque and throttle angle are higher than it would normally expect for a given engine speed (e.g. when towing) and it then adopts a different shift map (one of three, depending on the severity) which holds the transmission in its lower gears. Sounds unlikely for a continuous 80 miles though?

hi thanks for that not had the car long 3months found a pinhole in the expansion bottle today looks like previous owner had some pipework relaced to try and stop leak radiator looks fairly new as well is ther a way of finding out if its a hill mode causing prob without going to landrover of course thanks again

Mine has gone into cooling stratergy previously only came out of it once i parked up and switched off for ten minutes.

were you towing at the time or pushing it a bit ?

richard1 said:

were you towing at the time or pushing it a bit ?

Click to expand...

Hot day, been in town centre traffic on a saturday, long long steady hill of moderate incline for about 3 miles after that, and plenty of stop starting into and out of shops etc!

which gear did she lock in ? if you wre in traffic was she changing up and down repeadly? mine only did it whilst towing uphill i think all these gearboxes have a mind of there own mine is running perfect since taking caravan off must get diagnostic done before next trip

richard1 said:

which gear did she lock in ? if you wre in traffic was she changing up and down repeadly? mine only did it whilst towing uphill i think all these gearboxes have a mind of there own mine is running perfect since taking caravan off must get diagnostic done before next trip

Click to expand...

Change the oil and filter.

richard1 said:

which gear did she lock in ? if you wre in traffic was she changing up and down repeadly? mine only did it whilst towing uphill i think all these gearboxes have a mind of there own mine is running perfect since taking caravan off must get diagnostic done before next trip

Click to expand...

Wouldn't change above 3rd....

No repeat, but as preventative maintenance I changed the GB Cooler, Thermostat valve and base plate just to be sure!