Secon Gear runs to 48mph before shifting. NEED HELP

I just bought my 97 gtp and for some reason it only will hift into 3rd gear at 48 mph or above. i have a 2000 gtp and never experienced this problem at all, i want to get this fixed but do not want to pay shop rates to have it done. if anyone has had the same or similar problem let me know. i dont know when the filter was changed, i thought it might be that the filter is stopped up and has to build more pressure by getting to a higher rpm to shift but i could be completely wrong. thanks

or a bad 1-2 shift solenoid.

thats what i was thinking, but wanted a few opinions on it first. is that a drop the pan job?

If you have a bad soleniod you will lose two gears because of the configuration of hwo they are used.

This is an example..I doubt it's right

.... Sol1.. Sol 2
1st Off....Off
2nd On....Off
3rd On.....On
4th Off....On

Most likely you lost the 3rd gear sprag or 3rd clutches. Our transmissions are known for both.

no that isnt it, i have all gears, and tcc locks up through 3rd and 4rth, just takes a higher rpm to get third. im still leaning toward a stopped up line, or bad filter causing loss of pressure and therefore not allowing a shift until enough pressure is built. it may be it but may not, but im definately getting all 4 gears and lockup.

I guess a leaking channel plate gasket could be at fault. Only one gear though, right?

yea, just going into third. no fluid leaks that i can tell besides a leaky valve cover, i mean i only paid 2400 for the car and other than that its in mint condition, but it bugs the piss out of me through in town driving when i dont get to 45-50 mph and its like driving in second at high rpm. wasting fuel is my main issue. just need to fix it. and also how the hell do you remove the governor? i can only do 100, i get there fast as hell but once im there it cuts down on me. i dont want to buy a flashed pcm, is there a way to get around that? please help