1994 Grand Prix SE Transmission Help

[Godofwarmike]

Ok so i bought a 94 grand prix SE a few days ago and it is in good condition. I checked the fluid levels and the tran. fluid was low and had a burnt smell so i changed it and the filter. I took it out for a drive after and it won't shift into 4th gear it just sits in 3rd and runs at about 3,000 RPM at 55. Sometimes if i manually shift from 1st to 2nd to 3rd to D It will shift into 4th but only for like 10 secs then it goes back into 3rd. i tried adding Lucas Transmission fix but it didn't help any. This car also sat for a few years without being driven/started.

[tblake]

Did you install a new filter seal? Just wondering.

What type of fluid did you use?

When it shifts into 4th, does it slip, or is it a good clean shift?

[Godofwarmike]

Yes i replaced the filter seal.

I used Valvoline ATF Dexron III / Mercon Transmission fluid.

When it shifts into 4th gear it rides smooth just like all the other gears but goes back to 3rd. It also seems like the gear shift isnt quite right cause when i put it in 1 it will shift into 2nd too but when i place it in 2 it doesn't shift up and when i put it in 3 it goes to 3rd but sometimes goes back to 2nd then when i put it in D it will go to 3rd but sometimes it will go to 4th for like 10 seconds or so. But when i put it in R and N and P it seems to be right on. I checked some of the connections that run over top of the transmission and they don't have any corrosion either. Also it had this same problem before i changed the fluid/filter.

[tblake]

With your key on, engine off, put the gearshift in neutral and attempt to start the car. if should start.

Also you could try ohming out the TPS sensor, look for a good clean sweep as you push the pedal down further. Any sharp drop offs (dead spots) and its toast. Do this with the engine off. Although I doubt this is your problem.

You didnt overfill the tranny did you?

[Godofwarmike]

Ok ill try starting it in Neutral tomorrow and see how it goes.

How would i check the TPS since there are 3 wires?

I added tran fluid till it was in the hatched marks at idle then took it for a drive let it sit for about 10 mins and checked it again at idle still in hatched marks.

[Godofwarmike]

sorry forgot some extra details. The car as 117188 miles on it. when i put it in R it sometimes doesn't turn on the Back up lights. When i tried to start it in N it wouldn't start but when i changed the gears a few times it started.

[tblake]

Yeah, it wouldn't start in neutral? Sounds like it could be a bad PRNDL switch. The "no backup lights in reverse" problem also points to a flaky PRNDL switch.

Problem is I'm not sure how its possible for a bad PRNDL switch can affect a car not going into 4th.

I'm not sure the price on them, but if they are cheap, I'd replace it just to fix one problem before overdiagnosing another. (who knows it might clear up your 4th problem)

The PRNDL switch is located on the driverside of the trans. Its connected to the gearshift cable and is held in by two (13mm?) bolts. should easily be able to get at it from under the hood.

BTW if you do decide to get a new one, remember, it has to be adjusted.

(or you could try adjusting your current one)

-Start with the car off and set the parking brake
-Place the car in Neutral
-Find the PRNDL switch and loosen (dont remove) the two bolts holding it to the trans
-Have an assistant jump in the car and attempt to start it
-if no start have the assistant hold the key in the start position
-you go grasp the PRNDL switch and adjust it one way or another untill the car starts
-Tighten the bolts down
-Attempt to start the car in both Park and Neutral, and verify your backup lights function
-repeat process untill everything works, test drive.

[Christ]

If it's not the switch (likely isn't) then the shift linkage is loose/worn. My wife's '94 has the same problem, with almost the same mileage...

If you shift it into D by just pushing the shifter down, it will sit the indicator in D, but will not shift into "overdrive" (4th gear), whereas, if you just pull the lever forward and pull down one click from neutral, it's fine..

She's gotten used to it, so I don't plan on fixing it... also because it wouldn't be worth my time since I'm putting GT seats, center console, and floor shifter in her car.

[Godofwarmike]

Ok so i adjusted the PRNDL switch and it starts in N and the back up lights work all the time now. Still didn't help with the 4th Gear problem. so i looked at the shift cable and it seems to be putting it in the correct gears and doesn't seem to be loose. Took it for a drive and if i can get it in 4th gear it will stay for like 10 secs then pop out into third sometimes i think it pops out into second. I really need help cause this is costing me a fortune in gas. ($60 for 100 miles!!!)

[tblake]

That is excessive gas.

Is 4th gear slipping when it engages by chance?

[Godofwarmike]

it engages into 4th and drives like a new transmission and runs a tad under 2k rpms but then acts like it locks the converter up and bogs down to like 1400 rpms which makes it downshift into 2nd then back to third. to get it into forth i have to get to 55 then let off the accelerator shift into 3rd then put it back in D

[Christ]

something isn't right inside the tranny... probably a blocked fluid passage or something... get some tranny flush, (more) new tranny fluid and another new filter, and a can of Lucas transmission oil treatment, go ahead and change your fluid again... worst thing that will happen is the tranny is actually bad, and you've just wasted a lil money on new fluid and filter and lucas.

Honestly, the way you're sounding tho, you've got something wrong in the tranny, and it's probably something that doesn't require a complete rebuild... plugged/partially blocked passages will do exactly what you're describing.

[Godofwarmike]

Ok so i finally fixed my Transmission. The PRNDL was still a little shady sometimes if i wiggled the shift lever a bit the reverse lights would come on. and it wouldn't always start in Neutral. SO i looked around and found one for $30 (Great Deal at NAPA, Autozone $75, Advanced Auto Parts $170, Dealer $200) so i just put it on and adjusted it took it for a test drive and it finally shifts into all gears perfectly. Turns out the old ones seal split open on the bottom and was allowing water and crap in there screwing it up. The Automatic door locks work better too. It auto locks when its placed in any gear where as before it only locked when i was going 10 mph or faster.

[Christ]

sweet deal, glad to hear you got it fixed.

[tblake]

Good Job!