Gearbox Pulling Problems

We have a 1993 (K Reg) Volvo 850 GLT 2.5 Petrol Automatic Estate which has done 150000 miles. Over the past couple of months it has developed a strange problem with the gearbox If we stop at traffic lights (or another hold-up) when the engine has warmed up, then go to pull away again, the engine looses most of its pulling power resulting in a very slow take off, then after a few second there is usually a bang, the car lurches forward and all the power is resumed. Could this be a gearbox fault or could it be something else? We have also discovered, it's only when the car is warm that the problem occurs, it doesn't happen when the car is cold. Thanks

Check the colour and level of the gearbox oil.

Sounds more like a sensor problem of some sort but I'm not that clued up on autos, I'm sure someone will be along to help you out shortly.

Anyone else got any suggestions? Thanks.

change the oil!!! i think the gearbox has a filter aswell change that!!

The cheapest thng you can do is change and flush the gearbox fluid. I would expect that at 150k it's going to need it. Use Dexron III fluid. Search this site or look in Haynes for for the correct method. Doing anything else is going to cost much more than the car is worth to fix.