Engine/Transmission (1994 - 1998) Transmisson not going into 1st gear when I down shift!

[edgeman]

I just recently put a ats diesel transmission in my truck and I absolutly love it. I have a problem with the transmission not wanting to shift into first when it gets hot! Does any body know what the problem could be also I am running right around 80 psi in the lines at idle!

 

[Vaughn MacKenzie]

Are you saying it doesn't downshift when you manually select 1st, or is it taking off in 2nd gear because it doesn't shift into 1st on its own?

 

[edgeman]

it shifts into first when I manually do it but it won't on its own.

 

[Ahopper]

when i got my DTT trannie i noticed something simmaler when i was down shfting. if i manually selected 2nd it wouldnt shift there till about 30-35mph. and 1st gear till 15mph i belive. if i put it in OD Off then 2nd it would shift into second and then 1st it would also. but OD off has to be selected.