Overdrive the transmission will shift fine through 1st second and third but it wont go into over drive unless I let off the gas completely but if I try to matain speed then it goes right into third again

Solenoids inside the transmission or the control module.

Check the fluid level. You may want to consider having the transmission flushed. (I recommend BG Products flush system.) Properly flushing the trans removes any varnish the may have built up causing erratic behavior.

I have a 92 Crown Vic first and second works fine reverse works fine when it shifts in the third gear it goes to slipping and overdraft can you help me fix this problem thank you

This is a computer shifted transmission, if there is a problem with the electrical shift solenoids the system will set a code. Aamco does this code testing from free, I suggest you have them hook it up and see what shows up in the computers memory.

The "overdrive unit" is ready for an overhaul,or the transmission needs a fluid and filter service.

If it won't go into overdrive a speed sensor within the transmission may not be sending the shift signal to the transmission. Check fluid levels to make sure that's not causing the problem. Also, check that the fluid is red color and clean.

Transmission probably needs to be serviced at a reputable shop if you want this problem fixed.

be 1988 and Im sure it has high miles, sound like worn transmission, transmission flush and replace it with new fluid might help some. get use tranny from a junk yard better and cost lot less than rebuilt. being GM mechanic for many years i see transmission on a truck with 100k tend to have leaks or need rebuilding. again i see some have better luck but rear.

this could be relative to many things, however you should check a few things before asessing the possibilities. When you put the truck in gear from park, Drive (overdrive) Should be the third notch you come to. so your in park, pull down clunk you're in reverse, clunk you're in neutral, clunk, now you are in drive. If you dont feel/ hear four notches/ clunks, you should be in overdrive. If you take off and it over revs 1st ( you shouldn't see more than 15 mph before it shifts on a stock transmission unless your flooring it and taking off fast) and then hard shifts to second gear, progresses to third gear normally, but wont progress into overdrive, it may be related to your vaccum advance, your shift linkage, or even possibly your timing. From the sounds of it, I would say vaccum advance is the likely cause, if it is otherwise in stock condition. If this is the case it could be as simple as reconnecting a vacum hose to the distributor. Should be to the left hand side of the cap, between the cap and intake manifold as you are looking at the firewall.

You are going to need the transmission rebuilt.

Test the transmission module. It controls everything the transmission does, the timing of shift points, gear selection, overdrive, etc