240D very sluggish in first & second gear...

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I bought a '78 240D (auto trans.) the other day for about $700, and it seems to be even slower than usual in first and second gear. It's not an overall lack of power, because it gets up to about 75 mph on the interstate, and doesn't slow down on hills much once it gets going. It seems to take forever to get going, especially if the road's less than 180 degrees. I drove a 240D years ago, so I know they're almost like a Geo metro in regards to power, but I wonder if there's anything that could be causing this.