Transmission not shifting 1-2

I have a 1995 4WD S10 Blazer with a 4.3 engine and an automatic transmission. For information, I swapped engines about 3000 miles ago replacing the original with another S10 4.3 liter. The transmission will not shift out of first unless I back off the throttle. This just started to happen all of a sudden. It does not appear to slip in any of the gears, and seems to downshift well, including going back into first. The transmission fluid is burnt - light brown for now. I bought the vehicle used, so I do not know when the fluid was last changed. I am going to start with a new filter and fluid, plus Lucas additive (unless this is not a good idea). Any suggestions on other items to look into while I have the pan down and any other comments would be appreciated. Thank you.

I would hold on the Lucas for.

Get a good filter in it and see what is in the bottom of the pan.
Need to be put on a transmission capable scanner to see if shifting is electrical problem or other.
Post back any codes.
MT

Thanks for the info MT. I pulled the pan down tonight, and it was clean - no metal, not much residue in the pan either. The magnet was clean. I just closed it up and will put oil in it, but I will hold on the Lucas as you suggest and then get codes.

Checked it out at a transmission shop - 2-4 bands are gone, and so is second gear - trans is out for rebuilding.

burnt and dark fluid is the first dead giveaway of a toasted tranny

:(

I was hoping it was not a toasted tranny and was "willing" it to be something else. My "willing" powers are not too good.

Jeff

I have a 1995 blazer that wont drive right. I have to constantly ease off the gas and then gun it to get into different gears. It makes a loud whistling noise whenever i press the gas pedal when driving. And when i ease off the gas the noise eases up and its quiet if im cruising down a hill or something. Also along with the whistle is another noise, maybe a "vibrating hum". this noise acts the same, hear it when i hit the gas and goes away when i ease up. Almost stalled going up a hill today, sputtered but jammed on the gas and it made it up. Another thing is pressing the gas harder doesnt really make me go faster, taking a long time to build up any speed. Im new to this, so hopefully im posting it in the right place. If anyone can help i'd sure appreciate it.

I have a 1995 blazer that wont drive right. I have to constantly ease off the gas and then gun it to get into different gears. It makes a loud whistling noise whenever i press the gas pedal when driving. And when i ease off the gas the noise eases up and its quiet if im cruising down a hill or something. Also along with the whistle is another noise, maybe a "vibrating hum". this noise acts the same, hear it when i hit the gas and goes away when i ease up. Almost stalled going up a hill today, sputtered but jammed on the gas and it made it up. Another thing is pressing the gas harder doesnt really make me go faster, taking a long time to build up any speed. Im new to this, so hopefully im posting it in the right place. If anyone can help i'd sure appreciate it.

Welcome to AF
On your problem you need to start your own Thread/post.
On right side right above post hit the New thread button and give all of the info on it.
MT

I cant find anywhere that it says new or new thread anywhere.

Go to the forum and look at left side right over the poston left side.
MT