Transmission/ Speedo problems

[MG's VH Wag]

Hi guys, i recently put another transmission in my car because my previous one was stuffed. Anyway I have been having some trouble with the speedo which seems to be effecting the transmission. On some days, most of the time cold days when i leave home my speedo doesn't work and my car won't shift out of 1st unless i give it a bit then take my foot of the accelerator then it shifts into 2nd but then the light comes on and it won't shift back to first. Also i have been driving along and then my speedo will drop to 0 and the revs to about 700 and i think it goes into "Limp Mode" or whatever but if i pull over and wait for a couple of mins, start it back up then its fine.

Could there be a problem with the wires that go from my speedo to my transmission or a problem with the thing that sits in the side of the transmission which the wires from the speedo go in to (sorry i forgot the name of it)?

Any help would be appreciated, i just want to get it all running fine.

Cheers!

[MG's VH Wag]

Could there be a problem with the wires that go from my speedo to my transmission or a problem with the thing that sits in the side of the transmission which the wires from the speedo go in to (sorry i forgot the name of it)?

I think its called the transducer or something.

[hako]

What codes are you getting? - that should point you in the right direction hopefully.

[MG's VH Wag]

How do i check for codes? Sorry i don't know much about the computer side of cars.

[hako]

Check out this "how to"
Checking error codes VR/VS (Revised)