WS jerks real bad when put in gear

It's been a while, but I'm back for more good advice. My 98 windstar has been giving me a few problems. At times it would simply shut off and not want to start. I had to soak a rag with some gas and place it between the air flow mass and air cleaner to get it started. I've already determined that the fuel filter or fuel pump are not the culprits here. Today I drove my WS to work and as I was coming home this evening, I suddenly heard a loud thumping noise coming from below the hood while I was doing about 60 mph. I had a heck of a time getting to the slow lane because of the congested traffic. I then decided to get off the freeway and put the WS in neutral but it seemed to be in drive and moving slowly. I managed to get to a parking lot at an auto zone.I looked under the hood and checked the transmission fluid, it seemed very light in color and had an unusual smell to it. Anyone have any idea what I may be looking at to get it fixed? I've had this WS for almost ten years and has been a great vehicle for us, so I'd really hate to get rid of it.thanks for any and all help and ideas you all may have. I noticed yesterday that when I start it and try to put in gear, it will not move and then suddenly jerks real hard. When I first started to heve the problem with the jering it would go for just a bit and start making a loud noise and act like it had no fluid in the transmission and start slipping.

Thanks to all

The best advice would be to get it to a good shop to have the transmission evaluated.
If you do not know of one....ask around.
They will be best able to get right down to the problem.

Thanks Wiswind. As of last night it simply would not go froward or backward. I am going to take a close look at what it involves to eitjer replace the transaxle or fix the one in it. I had a really bad experience with a transmission shop some years back. I was charged about 1200 to rebuild my transmission and it started messing up real bad after about a month, I took it back and they tolfd me that the problem with the transmission ws not covered by the warranty. I've heard some similar stories over the years from people I know. If it's more than I can handle, I may not have a choice. I am just wondering if I can pull the transaxle out without pulling the engine out.

I honestly think that getting a quality re-manufactured transmission is the way to go......as rebuilds often only replace what is broken....and a few guesses at what might fail....and you still have a stressed rest of the transmission.
I know personally that a reman unit hurts.....I paid over $2800 for a Genuine FORD reman (including installation) unit in 2001.......and have put 83K on it.....and it is still shifting "perfectly" as the mechanic who went over my vehicle for me told me just 3 days ago.
When I was faced with the problem, I read up on the internet about a number of people who tried the rebuilt units that were 1/2 the price....and a year later were faced with another failed transmission.
So.....it hurt.....as it did not fit into my financial plans at the time....but I am very happy with the results.

Even having a dealership do a diagnostic......yes it will cost.....would be a good idea.....versus putting parts in that "might" fix it.
A competent mechanic with the right tools and diagnostic equipment will be able to give you a accurate picture of the situation......and with a clear understanding of the situation....you can decide what the best course of action will be.

I concur with WISWIND....I have had 2 reman xmissions installed at dealerships. one a Chrysler ($2600.00 in 2000) and one a Mercury....($3000 in 2005). Both came with 3 year 36K warranty and both are still running strong long after that. OEM is still really the way to go.