I think this is an electrical problem. There'* a bushel of wires that plugs into the transmission, and mine cracked. I "fixed" it with some speaker wire, and it'* held up for over a year. When the wire was cracked, the car wouldn't shift into fourth, but it would go into third and then shake. "Fixing" the break made the car shift into fourth, but very strangely.

I have to use cruise control for the car to be in 4th gear. Even the slightest tap of the gas pedal shifts it straight into 3rd and will never shift up, not even with crazy/soft/no driving, unless I shut off the car and start over. Sometimes, if I'm using cruise control in 4th to go up a hill, it shifts down even then to 3rd. As far as I know, there is no overdrive in my car.

I've scanned this, and the scantool told me it'* a torque converter clutch failure. However, if I unplug the car'* batteries and capacitors for a few minutes and plug them back in, with the computer reset like this, the car shifts even better and with more easily maintained acceleration goes up to any speed before 45mph. Past this speed, it will also shift into fourth gear without cruise control, but if I let go of the gas and press it again, or if I slow down or stop, I can never get back into fourth gear unless I restart my car and accelerate with only cruise control.

However, I can run WOT to about 65 (from a ramp or something onto a highway), and if I in the midst of this I turn on cruise control and set it when I let go of the gas, most often the car will stay in fourth gear. 70mph in fourth gear is about 2800rpm, and if I screw up the cruise control, it goes up to 3500rpm. I don't believe I have an overdrive.

Lastly, if I've already gone through the process to get stuck in 3rd and I gun my car, it will go to about 87-90mph and hit a rev limit at 5500rpm. It will never shift up and will continue bouncing between 87 and 90. This is perhaps awful, and I've only done it once. I think this can be easily solved by replacing that entire wire thing that plugs into the transmission and then goes into a hive of wires around the windshield washer fluid reservoir. A transmission place gave me a $30 quote. Has anyone else experienced this problem? I figured it would be common because the wires that plug into the transmission are fully exposed to heat, the elements, and various crazy people who think they're mechanics. The sheaths suck, so I figured the wires would break more often.

I have the same problem as in #2 on this link, but mine consistently goes into 4th gear:
http://www.bonnevilleclub.com/forum/...ic.php?t=86914

Bump. I am having similar problems with a 93 Bonneville SE. Sometimes it works fine, but other rimes it will drop back into third to make a pass and will refuse to go back into overdrive for the duration of the drive. the next ime I drive it it works fine. Is there something ( hopefully external) on these transmisions that controls when it goes into overdrive?

I have dealt with the same or a similar problem for over a year. I knew that it only happened once the trans got up to a certain temperature and could even run through most of the winter without problems. A couple of days ago I ran it until the symptoms returned and took it straight to a transmission shop where they ran the diagnostics. It showed a PWM solenoid failure. It was losing fourth gear and overdrive after the trans temp reached 60 degrees C. They are installing the solenoid and a few other upgrades as we speak. Hated to part with the cash but can't wait to put it on the road again.

this thread is 4 years old start a new one guys