2003 Mach 1 Question

Automatic transmissions are no fun to deal with when issues arise. Unless you are an experienced mechanic I wouldn't recommend rebuilding one. A replacement will run you about 2200 bucks. KBB blue books it at around 10 grand and NADA Guides indicates blue book on it is $10,800, so it appears the seller did leave enough cushion in the price for the transmission replacement. It could just need a servicing as well.

Good Luck!

It doesn't look too bad, but I would be worried about the automatic. First, as I posted in your other thread, I am not a fan of Mach 1 automatics. They run the same rotating assembly with the 6 bolt crank as the GT, thus, limiting its redline to ~6000 RPMs. The manual has a forged 8 bolt crank, and forged pistons allowing it to spin to ~6800 RPMS.

There could be a number of reasons the transmission is slipping. You can have someone rebuild the 4r70, or you can do it yourself. There are several videos and manuals that walk you through the rebuild process, but it can be tricky. You can just pick up a new 4r70 in a few flavors from somewhere like transmissioncenter.com. They have from mild to wild, $1800 for a stock version to $3k for a fully tricked out transmission. This is just an example, I have no experience with them, but there are quite a few places like this to get a new one. The last place to look, is eBay. I just looked and there are 4r70s from $340 and up.

The biggest thing you need to do, is go look, and drive it. If it runs and drives like crap, it might just be crap. If everything is great, except the transmission.....offer him a little less because you have to get a new transmission. Use the money you saved in the purchase and put towards the transmission option of your choice.