I have a 1997 SE with 86k miles on it (the last 3500 added just last week!), also no tranny cooler yet. I've only owned the car for about 2 months, so I took it in to get the oil changed and stuff at the dealership last friday before my roadtrip to Vegas. They inspected stuff and lubricated things. They said the serpitine belt was starting to crack and the tranny fluid was brown, both things listed as "may need to be serviced in the future" or something.
Next day, halfway across Nebraska the tranny starts to "surge" in and out of OD (rpms from 1800-3000, back and forth quickly) at about 80mph under light throttle. Put the tranny in "D", locking it in gear, so no trouble on the Interstate. Later, when driving around in towns, the car surged, rpms bouncing up and down about 500 rpm in the same gear. However, no check engine lights, so no codes. Stopped Monday morning in Colorado at a dealership, they flushed the tranny and dropped the pan to replace the filter and replaced the serpitine belt as well. Worked fine until on the way home again it began to do the small surging (500rpm) again.
Any ideas or help would be appreciated, thanks.

not sure if it covers '97, but i know there is a TSB for a surge when in lock-up [overdrive]. it usually causes a 500 rpm fluctuation at normal [45-60] cruising speeds. the repair is a new valve body. it has an updated tcc valve/bore configuration in the valve body. the original design valve/bore is 'loose', letting the valve drop fluid pressure/volume causing the valve to 'bounce' around in the bore, causing the converter to come on and off. i have replaced several valve bodies for this condition, but not sure if it started in 97 or 98.

hope this helps some

This is exactly what my 97 with just over 120k was doing. I sold the car last week but I'm going to let the new owner know if it acts up there may be a TSB out. Still means the customer has to pay for it though right..since its not a full fledged recall?

I have been fighting this problem for awhile. Everyones first suggestion is fuel filter, then plugs, wires, etc.
I have done all of these things, not to say it wont solve yours. I am going to a trany specialist that a friend recommended, hopefully next week. I will let you know the results.

I am under my wifes name on here so you dont think she is trying to answer your question. I had a similiar problem with a different GM car. Mine would not only surge and jump while driving but it got to the point where it started doing it when I would stop. It wound up being my torque convertor sensor that was located at the front of the transmission case. It'* only purpose is for fuel economy. I unplugged it and it ran great since. My brother in-law just had the same problem with his olds and did the same thing which also worked. Oh yeah the service lght doesn't come on since .

I've had the same problem since I turned about 70,000 miles. I recently had some work done to the engine [1.8 rockers larger TB and new underdrive pulleys]. The shop I used also does transmissions and confirmed the valve body diagnosis. He estimated the repair at approx. $300. But with the mods to the motor the hesitation/surge is much less noticeable. The trans. cooler will also help in that it lowers the operating temp. of the trans. which wil result in less slippage in and out of OD.

Also, will my gas mileage suffer from this OD slippage, or is bad mileage (with a 2 week old O2 sensor) an indicator of more, deeper problems (please, no ). Or I could just take that brick off my foot

AC Delco sensor bought from a GM dealership (had to buy it that day before roadtrip, ordered the wrong one from gmpartsdirect, oops). I'm round about 15 all in town all stopsigns, red lights every block, damn college town ... wait I go to college here so i guess thats not too bad. Again with the brick on the foot, too, probably.

I would have some answers for the fixes on this, but I'm unexpectedly poor at the moment, so I'm not going near the dealership for awhile. (I think they charge for the air I breathe :( )

Hi everyone,

I'm new to this forum...looks great so far!

I've been experiencing this 'surging' as well, ever since 90,000 km on the odo. I notice it between 70kmph and 110kmph and generally force the tranny to shift back to 3rd and then back to 4th to 'fix' the problem.

Has anyone found a permanent fix? or a closer view to the root cause?

TIA