lt1redmonster

Hey y'all, I'm a very new user here, I literally just signed up, so forgive me if this is in the wrong section or if this problem has already been addressed.

Getting down to business, for a little history on this car, Iv'e had it for about a month now, it has 109k on it, has been taken very good care of, had regular fluid and filter changes, overall, the maintenance has been very good. and it shows. It has the 4-speed automatic 4l60e.

Recently though, when i was driving home, I decided to lay into it a bit from a light, and the transmission failed to shift into second until I let off the throttle, but I believe that it may have just skipped second and shifted into third. I've been driving it how it is for about a week now, just letting off the gas to get it to shift up into the next gear from first. It won't shift unless i take it up to 3k and hold it, then release the pedal a bit. Then it shifts smoothly into whatever gear its going into. Alongside this problem, the speedometer has been acting very strangely, about 80% of the time, it is functioning as it should, but occasionally it will either completely just stop working, or it will read much much too high, indicating very high speeds while going 30-40, overall just being very erratic. The check engine light is not on, but i believe the bulb is burnt out or something because even at startup when all the lights on the dash come on momentarily, it doesn't light up. I have not run the codes on it, but that is on the list to do shortly. How the car is now, I can't floor it without it shifting down into what seems to be first and redlining itself immediately.. i have to let up a bit to have it shift, then it will continue. There are no jolts, absolutely no slipping, reverse and all the gears don't slip at all.

I have a few theories, maybe a bad VSS, or TPS, or perhaps a 1-2 solenoid? worst case a bad clutch pack?

I checked the fluid and replaced the filter for good measure, they are fine, and had a clean pan, no chunks or debris to speak of.

Sorry if thats a long read, but I'm trying to be as informative as possible..

shoebox

First order of business: scan for codes.

12SCNDZ

As already mentioned... Have it scanned. A bad VSS will store a code. The VSS does control the upshifts in a 4L60E. Is it shifting through all the gears? Are you certain it's not making a 1-3 shift? What condition is the fluid in? The 4L60E doesn't use a "1-2" shift solenoid, eventhough the book lists it as such.. Both solenoids are ON for 1st gear. The A solenoid goes OFF for 2nd gear while the B solenoid stays ON. This rules out the likelyhood of it being a shift solenoid..

Frank

12SCNDZ

Does it have overdrive (4th gear) and lock up?

lt1redmonster

It does have overdrive I believe, it will run at about 17-1900rpm on the highway 55-60ish mph how do I tell if it has lock up? (Not familiar with that term)

12SCNDZ

If you move the shifter from the O/D position to the D position while at highway speed, does it downshift? Lock up is when the clutch in the torque converter engafes. It's not usually as firm as a shift, but you will notice an RPM recuction. The easiest method to test lock up is to get the car running around 60 MPH at a steady cruise. Keep your right foot steady on the gas pedal, but lightly tap the brake pedal with your left foot. Tapping the brake should unlock the converter and you should see the tach jump up a couple 100 RPMs.

Frank

lt1redmonster

I just took it out for a spin, and it downshifted to third when I shifted into drive, and also the lock up part seems to be right on. I went to go check for codes at autozone and the scanner kept saying to check the connection and try again, tried even another scanner and it still wouldn't work.. The obd2 plug fit like it was supposed to though.. I'm not sure what to do about that.. Can't pull codes

Injuneer

Problem is Auto Zone tech saw the 16-pin OBD-2 ALDL connector on your 95, and used an OBD-2 scanner. Since your 95 has an OBD-1 PCM, it requires an OBD-1 scanner and the correct cable or a 12-pin -> 16-pin adapter plug. Do not use an Innova... they seem to produce a standard list of about 8 codes whenever they connect to the LT! PCM. Not sure why they don't work.

lt1redmonster

Ok, I called them and asked if they had an obd-1 scanner, they said no.. Called Midas and they don't have it either.. I have an appointment set up with a transmission and electrical specialist tomorrow, Hopefully they have one? I didn't think they would be this rare..

lt1redmonster

Anybody know where I could find a diagram of the wiring for the transmission? I want to check the wires and the VSS with my meter, but I'm not sure where to start

Injuneer

Shoebox has all the 95 PCM wiring diagrams, which include the transmission wiring, on his website.

shbox.com

The is a link on the"Computer Diagnostics....." forum to a free download of OBD-1 scanning software written specifically for the 94/95 LT1.

lt1redmonster

[QUOTE=Injuneer;6959370]Shoebox has all the 95 PCM wiring diagrams, which include the transmission wiring, on his website.

shbox.com

Thank you!