Funny burning smell!

Hi,

My dads having a problem that hes slightly concerned about.

Basically the quick version of the story is:

My dad tried to create a pully system using his G wagen(being the puller), my g wagen being the sort of pivot(think thats the right word!) and then the other G wagen that was being towed(engine doesnt start!)

He tried to pull the G wagen in using this pully system but wasn't at the right angle as it was in a tight space lol. Basically Loads of smoke poured out from under the g wagen and as soon as he stopped pulling the smoke dissapeared. We took it to the garage near us to make sure the clutch wasn't messed up etc etc(Full check over) and he said there didn't seem to be a problem and the only way to find out if there is is to drive it :)

Now we haven't had any problems with the merc or any burning smells since then (That was about 4 months ago) until last night. We were towing water bowsers around a Venue that needed a "big" car and we started noticing the smell again.

So does anyone have any ideas please
Many thanks
Joe