Originally Posted by tonyg
My 92SSE does the same thing. It kind of feels like it slips into overdrive and then hits a "dead zone" and yes it does feel as though you are driving over rippled pavement..kind of a low groaning sound. It seems to smooth out if you accelerate. I sure hope mine is not a tranny prob...hope yours isn't either. I had a problem where the car would actually buck at about 50-55mph and would not stop until you hit the gas harder. My mechanic changed my wires, plugs, pcv and that problem went away. The low groaning in overdrive is still there though....and so is my crappy airflow from the vents even after cleaning my evap core. I've come to appreciate the car and to overlook certain flaws as it is an overall good vehicle.
My first post!
I was browsing the forums and found this discussion interesting. I own a 1992 SE purchased used in 2000. About a month later, I began to experience this problem. Too late to complain about it to the seller. Oh well...
The symptom was exactly as described. A low 'groaning' vibration while cruising in overdrive. I could feel it through everything; the pedals, steering wheel, floor board, etc. My rear-view mirror would even vibrate so much I couldn't see anything in it.
If I backed off the accelerator, it disappeared, but would return again as soon as I resumed speed. If I gave it just a little more gas, the engine seemed very sluggish and the vibration worsened. If I pushed the accelerator down further, it would kick-down and power returned to the engine. It only happened while cruising in OD at 60MPH and above.
So I finally became annoyed enough after about 7K miles to take it into a local repair shop, who test drove it while connected to one of those OBD computer thingies and detected something going on with the TCC, converter, and transmission. They referred me to a transmission shop, who did much the same but performed a more extensive road test.
$1470.00 and a week later, I had a completely rebuilt transmission.
The vibration I experienced was converter 'shudder' at TC lockup. The converter was also slipping, fluctuating between 50~150RPM of slip according to the diagnostic computer. If I recall correctly, acceptable slip is supposed to be 20RPM or less. In addition to a bad TCC assembly, the rebuilder also found a few other internals with extreme wear, due in part to the vibration transmitting through these parts + increased heat.
I planned to drive the car from Michigan to California the following month with the car loaded to the max (I was moving to CA), so I wanted the transmission rebuilt for peace of mind instead of 'patched up'.
Anyway, it ran like a champ through the mountains at 75MPH+. It also runs 250RPM lower at any given cruising speed than it did before and fuel economy improved 4~5MPG.
If you haven't already, you might try replacing your trans fluid with the recommended Dextron III/IIe fluid. As the thread creator discovered, replacing the trans fluid will solve many cases of converter shudder caused by trans fluid that is 'expended' or adulterated by a transmission additive (Duralube, Slick50, Prolong, etc.).
Of course, it won't cure any excessive wear or damage that has already occurred, in which case your trans certainly has an overhaul in its future at some point, but if you could get another 25,000 miles with a $60 'fix' before requiring an overhaul, better later than sooner.