As some of you know my 2001 SSEi with 90k on it has been surging lately. 40 mph + under a slight acceleration will produce a surging that can be felt and seen in the RPM gauge.

I have replaced:

Spark plugs
Spark plug wires
EGR valve
Fuel filter
Trans fluid at 65k

I have also tightened every vacuum hose that I thought may be loose. Then it was suggested to me that when the surging started up again to press on the brake just enough to get the brake lights to come on which would "kick out" the torque converter to see if the surging stopped and yes it does. I can reproduce this at will.

So my questions are if I am looking at a new torque converter where do I go, what do I look for, what do I buy, and how much should I spend?

Thanks.

On the way for the Yeller M&M post

Paul... check this out.

http://www.bonnevilleclub.com/forum/...t=ground+strap

It'* a bit of a read, but this is directly from the GM FSM for the Bonneville:

Torque Converter Clutch Shudder

The key to diagnosing Torque Converter Clutch (TCC) shudder is to note when it happens and under what conditions.

TCC shudder which is caused by the transmission should only occur during the apply or the release of the converter clutch. Shudder should never occur after the TCC plate is fully applied.

If the shudder occurs while the TCC is applying, the problem can be within the transmission or the torque converter. Something is causing one of the following conditions to occur:

* Something is not allowing the clutch to become fully engaged.
* Something is not allowing the clutch to release.
* The clutch is releasing and applying at the same time.

One of the following conditions may be causing the problem to occur:

* Leaking turbine shaft seals
* A restricted release orifice
* A distorted clutch or housing surface due to long converter bolts
* Defective friction material on the TCC plate

If Shudder Occurs After TCC has Applied

If shudder occurs after the TCC has applied, most of the time there is nothing wrong with the transmission.

As mentioned above, the TCC is not likely to slip after the TCC has been applied. Engine problems may go unnoticed under light throttle and load, but they become noticeable after the TCC apply when going up a hill or accelerating. This is due to the mechanical coupling between the engine and the transmission.

Once TCC is applied, there is no torque converter (fluid coupling) assistance. Engine or driveline vibrations could be unnoticeable before TCC engagement.

Inspect the following components in order to avoid misdiagnosis of TCC shudder. An inspection will also avoid the unnecessary disassembly of a transmission or the unnecessary replacement of a torque converter.

* Spark plugs - Inspect for cracks, high resistance or a broken insulator.
* Plug wires - Look in each end. If there is red dust (ozone) or a black substance (carbon) present, then the wires are bad. Also look for a white discoloration of the wire. This indicates arcing during hard acceleration.
* Coil - Look for a black discoloration on the bottom of the coil. This indicates arcing while the engine is misfiring.
* Fuel injector - The filter may be plugged.
* Vacuum leak - The engine will not get a correct amount of fuel. The mixture may run rich or lean depending on where the leak occurs.
* EGR valve - The valve may let in too much or too little unburnable exhaust gas and could cause the engine to run rich or lean.
* MAP/MAF sensor - Like a vacuum leak, the engine will not get the correct amount of fuel for proper engine operation.
* Carbon on the intake valves - Carbon restricts the proper flow of air/fuel mixture into the cylinders.
* Flat cam - Valves do not open enough to let the proper fuel/air mixture into the cylinders.
* Oxygen sensor - This sensor may command the engine too rich or too lean for too long.
* Fuel pressure - This may be too low.
* Engine mounts - Vibration of the mounts can be multiplied by TCC engagement.
* Axle joints - Check for vibration.
* TP Sensor - The TCC apply and release depends on the TP Sensor in many engines. If the TP Sensor is out of specification, TCC may remain applied during initial engine loading.
* Cylinder balance - Bad piston rings or poorly sealing valves can cause low power in a cylinder.
* Fuel contamination - This causes poor engine performance.

Torque Converter Evaluation and Diagnosis

Replace the torque converter if any of the following conditions exist:

* External leaks appear in the hub weld area.
* The converter hub is scored or damaged.
* The converter pilot is broken, damaged, or fits poorly into the crankshaft.
* You discover steel particles after flushing the cooler and the cooler lines.
* The pump is damaged, or you discover steel particles in the converter.
* The vehicle has TCC shudder and/or no TCC apply. Replace the torque converter only after all hydraulic and electrical diagnoses have been made. The converter clutch material may be glazed.
* The converter has an imbalance which cannot be corrected. Refer to Flexplate/Torque Converter Vibration Test .
* The converter is contaminated with engine coolant which contains antifreeze.
* An internal failure occurs in the stator roller clutch.
* You notice excessive end play.
* Overheating produces heavy debris in the clutch.
* You discover steel particles or clutch lining material in the fluid filter or on the magnet, when no internal parts in the unit are worn or damaged. This condition indicates that lining material came from the converter.

Do not replace the torque converter if you discover any of the following symptoms:

* The oil has an odor or the oil is discolored, even though metal or clutch facing particles are not present.
* The threads in one or more of the converter bolt holds are damaged. Correct the condition with a new thread inset.
* Transmission failure did not display evidence of damaged or worn internal parts, steel particles or clutch plate lining material in the unit and inside the fluid filter. *The vehicle has been exposed to high mileage only. An exception may exist where the lining of the torque converter clutch dampener plate has seen excess wear by vehicles operated in heavy and/or constant traffic, such as taxi, delivery, or police use.

Sorry...the yellow M&M was out for a memory upgrade.

Before signing the torque converter'* death warrant, if you have symtoms like this (pulled out of the other post), it could very well "just" be the grounding strap.

Prior to that, either as a result of preventative maintenance, or tracking down a "check gas cap" warning, or this problem, I had replaced or swapped out, plugs, wires, O2 sensor, TB MAF IAC, cleaning (during LIM gasketwork), TPS sensor, coils, ICM, fuel filter, evap system, vacuum lines and checked fuel pressure. Nothing eliminated it. The problem still has not returned after cleaning up that ground.

Edit - FWIW, I too was starting to fear a problem with the torque converter. I forgot that it also had the fluid flushed in tranny.

Mine did that once.
I found it was a rear spark plug wire that was touching the O2 sensor. I moved it so it wasn't touching and the surging went away.

my surging was reduced when I checked the plug and play TPS and modified it to be adjustable. Reset to the center of the factory spec., and surging has been reduced to only hot summer days climbing hills at 40mph. Fluid temp has a lot to do with it. I think the fluid breaks down and becomes too thin IMO.
Other inexpensive things you could try:
* Change the fliter, the fluid pressure could be too low due to clogging.
* Add a conditioner, most trans shops do to eliminate shudder.
If you are seeing rpm changes you no doubt are experiencing clutch slippage.

If I drop to third gear from OD and I no longer get the surging under the same conditions I was while driving in OD does that tell us anything?

Exactly the symptom I posted ^^^^, that cleaning the grounding strap cured.

I've been trying to get to that, but it'* too cold. I'm a wussy.