i have a leak that seems to be coming from the area where the trans bolts on to the engine, and a friend of mine who works on these vans said it is probably the front main seal of the trans leaking, and that the best thing to do is have it rebuilt. Even though it works fine, it would have to be taken apart to fix the seal and he knows someone that can rebuild this transmission, which i believe is called the 400 turbo HD, for $450 - and that is the best deal i will find.
Has anyone else had a problem like this? Is it even worth trying some of the products like Lucas transmission stop-leak or whatever it is called, or will that just do more harm than good?
thanks,
Paul

Don't waste your time or money with stop leaks, they don't work. If you have a leak, it is most likely a bad seal or o-ring or leaking converter. Find a reputable trans shop and have them fix what is broken, unless they find something else that needs attention.;)

The transmission front seal is not that hard to change out. I have changed out the 350 front seal and the 400 is probably similar. You should be able to do the job on a Saturday morning if you have the mechanical skills and jacks or wood blocks. You can rent a auto trans. jack. (makes it a lot easier).

I would start by removing the flywheel cover, washing the whole area off with brake-clean, running it at idle while looking up underneath, flashlight in hand! I've seen convertors leak under pressure at the lug welds. They will spray little droplets of fluid out and all over your safety glasses!

The front pump seal is not on the flywheel end, it's between the front pump and the convertor. If it leaks, the oil will run down between them and drip on the front edge of the pan.

There's no seal to leak where the convertor meets the flywheel/engine. If the leak is coming from that area, it's likely the convertor and would need a replacement.

If the trans operates normally, there is no need for a rebuild. Just replace the leaking parts and go for it! The front pump seal is easy to replace on a 400. Not so with the 700. They require a retainer and careful installation procedure or they will build pressure behind the new seal and blow it out. There are several bulletins on different procedures to help prevent this problem, including drilling a relief in the pump housing behind the seal. Not a job for the first-timer. It's a PITA!