Hi All.
I have an 03 club cab, done 80,000 had a problem for the last 3weeks engine runs fine for 20 mins or so drives well and then when slowing down in traffic there is a strange noise, almost sounds like another engine along side and then when I stop at lights or a junction there is a loud clunk , and the 4wheel drive light comes on and flashes,and when I pull away the noise has gone the light flashes for approx 10to15 mins drives well again untill it repeats itself all over again at various intervals.
Took it too a garage they say I might need a new gear box!!!! But there has been no clunking in and out of gear and there is no problem when going through the gears.
They took it for a test drive ,I wasn't with them and of course the noise didn't happen, I don't think they drove it long enough ?
Many thanks for any comments or suggestions on what the problem could be.?
Mike.

Losing vacuum from the system when revs are low, need to give the vac system a once over but you'll naad a vac guage, ( about £20 from the Bay of E's)... very likely a pipe with a split in, that needs replacing..
Whereabouts are you..?