1995 XLT 3.0L

No warning signs.
From one day to the next, no OD.
When selecting OD, it feels like it is staying in 3rd and refuses to upshift, even at highway speeds.

Gears 1-3 & R are solid.

What should I be checking?

 

OD is engaged electronically, so the main things to look for is either that the computer is not seeing the signals needed to engage OD, or that the solenoids involved are not functioning correctly.

Possible culprits include the vehicle speed sensors, a computer fault that triggers open loop mode, or several other similar problems.

 

Check OD shift solenoid resistance, wiering, pull codes to be sure it is ok.

If you are sure OD solenoid is good, try to ajust OD band.

 

Are you getting any warning lights on the instrument panel? Are all the brake light bulbs working? A failed bulb will cause all sorts of things to stop working, including the rear ABS, transmission lock up, and cruise control. (and 4wd if you have that)

 

Hi Bax2008,

Welcome to our FTE forum

There are only 2 solenoids on the 95 A4LD. One is for the 3-4 shift and one is for the Torque Converter lockup. I don't know if the Overdrive is controlled by any of these. I'd have to check the manual after I get home to be sure.

From a complete stop you should feel the following 4 slight jolts:

1-2
2-3
3-4
T/C lockup (about 40-45 mph)

If you are missing the last jolt, it could be either one of the solenoids.

Come to think of it, you should feel all 4 jolts regardless of whether you are in D or OD, so what you are describing may not have anything to do with O/D.

 

I'll check the wiring this afternoon. Thnx.
I read somewhere that the TPS is often the culprit. Opinions?

 

No warning lights.
I'll check the bulbs later today. (that's a weird one)

On that note, just recently, my radio lights flash when my left turn signal is on (without the headlights being on).

Thnx.

 

Check all the fuses - even the ones that don't seem related.

I recently had the speedo quit on my 95 3.0 XLT, and at the same time it stopped shifting into OD. Turned out to be a blown fuse for the interior lights...

The VSS system was powered off the same fuse as the interior lights (which I believe includes the instrument panel & radio lamps). A broken wire on the front passenger door light switch blew the fuse, which killed power to the VSS & the speedo.

The flashing radio light with turn signal sounds like a dead circuit being back-fed through a bulb.

Good luck with your troubleshooting.

Cheers,
Eric

 

any codes?
pull your own click
many ECU error codes prevent OD and TC lockup.

TPS problems usually show up as an intermittent due to the type of sensor it is. is your problem intermittent? TPS can cause OD or TC shift problems but look for more obvious higher percentage problems first

the stop lights provide a switched ground to the speed control unit logic which can effect OD and TC LU shifting
from Serv Manual

Pressing OFF turns off the system [grounds 151 (LB/BK) wire]. The system is also turned off when the brake pedal is depressed [removing the ground provided by the Stop Lamps through the 810 (R/LG) wire] or the Ignition Switch is turned OFF. The Vacuum Dump Valve also operates when the brake pedal is depressed. This is a backup device to release the servo.

operating an A4LD with no TC lockup will kill the tranny in a couple hundred miles from overheating

the guys have gave you a good list above

 

Thnx for the reply.

I checked all fuses in the fuse panel and they all seem fine.
Are there any fuses OUTSIDE the panel that should be checked?

I'll be trying to find the time tomorrow to climb underneath and check the OD wiring harness and connection at the transmission.

 

Thnx for the reply.

I'll check for the codes ASAP.

No, the problem does not appear to be intermittent. She does not want to shift into 4th. Period. Revs/engine noise at highway speeds are annoyingly high.

Forgot to check the brake lights today. Will check first thing tomorrow.

No OFF switch on this one. OD is on the column.

Good bunch on this forum. I'm lucky I found it.

 

I checked the brake lights just now. They are fine.


Thnx

 

PCM will prevent OD and TC LU if the thermostat fails open, is your temp gauge reading where it usually does?

if ECT or IAT fail, can also prevent OD and LU

 

Thnx for the response.

Temp is reading fine.
T-stat and both temp sensors have been replaced within the last year.

 

A Few Ideas...

You're having electrical probs with that wierd turn signal/ radio light deal (& switch wire blowing fuse prob).

I'd guess that was separate from your OD prob since signals on '95 use separate bulbs from brake lights. Otherwise they'd be connected. May still be connected especially if they began about the same time.

I think Copper mis-spoke because 3-4 shift IS the same as 3-OD. 4th gear is an overdrive ratio I believe. After that the torque converter should lock up.

Of course there's the possibility of mechanical failure.