Thank you in advance for the help.

I have a 97 Bonneville SSE. My trany went out a few months back and broke down and had the GM dealer install a new certified GM trany with the full warranty. After putting on 10,000 miles it started to surge when shifting and consistent surging at 70mph , almost like the lockout torque converter was slipping in and out. Brought it back in and they replaced the torque converter with a new one, and sent me on my way. Right away I notice the same surging issue. Brought it back in and they told me the 3rd gear seal was leaking, and that they put in a new seal kit.

Now, the surging is gone. But, now at 70mph cruising speed the engine is running aprox 500 rpm’* higher then what it normally did. Feels just like the torque converter is not locking out. Right now at 70mph it is running around 2400 rpm, were it use to run around 1900 rpm. At 70 mph with a light acceleration I don’t feel that “light down shift” were the torque converter would unlock. The only down shift I get is with a heavier acceleration and it drops down a gear and the rpm’* jump up 800/900 rpm. Plus, after lightly accelerating up to 70 mph I do not get the drop in rpm’* when the torque converter would lock in. The car started acting this way after they replaced the seals. I brought the car back to the dealer, and after they did there inspections they told me there is nothing wrong and that is running normal. Driving the car 160 mile per day I know for a fact that this is not “normal”, gas mileage has dropped.

I also notice that I now get a light down shift were the rpm’* jump up 300/400 rpm’* at around 40 mph when lightly accelerating from a dead stop 70 mph. Almost like the torque converter is unlocking at 40 mph and then never locks back in when reaching 70 mph.

My question is, what is the rpm range I should be at when cruising at 70 mph. I am kinda stuck between a rock and a hard place going up against the dealer, when I know this is not normal, but they say there is nothing wrong. I am not new to a wrench, and do all my own mechanical work, except rebuild tranys.

Any help is greatly appreciated.

Thanks
Bill

When driving on the expressway at a steady 60 MPH, touch the brake pedal lightly with your left foot. Enough to depress it but not enough to slow the car down. When you press on the brake the torque convertor should come out of lock up and the RPM'* should go up a little. If the RPM'* don't go up when you touch the brake the torque convertor is not going into lock up.

If the torque convertor is not locking up, take a look under the IP at the top of the brake pedal. There is a little plunger switch that contacts the brake pedal arm that detects when the brake pedal is switched. Is that plunger switch in good position to contact the pedal in the up position, and is it acuating when you push on the pedal?

Nope doesnt change when lightly pressing the brake at 60. And the switch on the brake pdl seams to be in good condition.

It is like driving a car without a lock-up torque conv.

Thanks

Tapping the brake at cruising speed should disengage torque converter lock up and cause an increase in RPM'* while maintaining the same road speed. Based on your observation I would agree the converter is not going into lock up. Need someone with more transmission knowledge than mine to determine next steps.

Thanks 2kg4u, that is what i was leaning towards. I think i will run it in to the local trans shop and get a writen estimate. The i will bring it back in to the dealer and get it worked out.

Thanks again.

Let us know what happens.

Thanks, I will do that.

Just a little update. Brought the car back to the dealer and they worked with GM on the issue. GM said it probebly was a bad trans casting with some porosity in the housing and shipped a brand new one out for replacement. Good news

Btw, I never got pissed off with the dealer over the coase of this hole deal. Something to be said when you work with someone in a professional way. The did a real good job with costomer service. And GM hands down has my respect.

Dealer, Thelin moters, park rapids, mn.