Transmission Overdrive?

[SuperChargedJoe]

Well my 97 Bonneville SE 3800 has been great all the way up to 126000 miles. Starting to get a problem with the trans fluctuating in and out of over drive at higher speeds. When on the expressway doing about 65-70mph the rpms will bounce between 2200-2500. To me it seems like it will go into overdrive and then fall out. I checked trans fluid and it is not burned and is a nice red color. Not sure if there is a sensor for it or not. Scanned the ECM had no fault codes. Any help would be great.

[SuperChargedJoe]

So now i'm thinking it may not be just a problem with overdrive, cause it seems to surge in 3rd gear also. Anyone else have this problem???

[myfirstbonnie]

Sounds ignition related, how old are the plugs and wires? Any SES light or codes?

[RJolly87]

It may also be the torque converter unlocking. When it is surging, does the cruise control work, or does it shut off? If you drag the brakes ever so slightly, does it stop surging?

[Archon]

I'm not sure when the switch was made to the '65E, but if you have it in your car, it could be the problem explained here:
http://tripleedgeperformance.com/TCC-rp ... ation.html

[dangrus4060]

My daughter's 97 SE has been doing the exact same thing since i bought it in 2006. Fine when cold, starts fluctuating when warmed up....eventually the ECM cancels the TCC lockup sets code and then it runs normal...just a few RPM's above what it should be when locked up...tranny fluid is still red...no other issues. Going on 60,000 miles this way.

[RJolly87]

I wonder if perhaps the brake switch is getting funky, or the TPS is getting weird too.