Can any one help me with what adjustment i can do to make it stay in 1st & 2nd longer

Check to see what gears you are running. You might have very low gears. Maybe 4.10s or something.

The car is a 70 Mustang i have onlt jsut got this car and in the notes it says 351W and an FMX transmission with 3.00 gears

What is this in?
Engine etc.

The FMX is in a 70 mustang with a 351W not sure what diff is in it but is doing 2800 rev's at 60mph

What speed does the 1-2 come in?

What happens when you downshift from D (high gear) to 2nd, then Low?

Can you kick it down into passing gear?

It kicks down everything works ok its just when i take off at a normal speed it is in 3rd gear by 20mph or less.
When i floor it in drive it will only get up to about 35mph then it shift in to 3rd unless i hold it in 2nd

Ok, by the sound of that either the governor or shift valves are hanging up.
My money is on the governor.

Remove the extension housing to have at it.

Thanks Stuart i will try that

Problem usually crops up with a shift kit. Then it's not the governor. Unless you know the history of the transmission anything's possible. My bet? It's the valve body.

In the notes i got with the car is said the transmission rebuilt with a B&M shift kit

You did not mention a shift kit.

That makes a huge difference.

B&M, yick.

Valve body it is.

what shift kit should i put in it?

The stock valve body works great. After going through the same symptoms you have I decided not to do any more valve body kits until my customer was satisfied. Then I would service it again with the kit and I told you so.

However, me? I raced my FMX for years and loved it and it needed the kit (I have both TransGo and B&M kit prepped v/bodies). I was shifting at 7500 on the giggle gas...

So, what to do? I would contact our sponsor (Broader) and talk to him about the issues. Mention the kit of course! Servicing a VB in an FMX is not for the first-timer unless you're good. Are you ? Seriously, it takes patience and good skills. It is NOT difficult.

HTH.

Computer stutter.

FMX's worked good right out of the box.

In fact they will take a licking and keep on ticking.

If a shift kit is needed Transgo is about the best.