05 Impala transmission

05 Impala LS 3.8; 85,000mi

My Impala transmission seems to slip on take off intermittently. It can go a month or two without doing it or several times over a couple weeks. It will happen whether hot or cold but most often after running for a few minutes. It happens after stopping at a light. The car starts moving a few feet then suddenly the transmission grabs. The harder the acceleration the more it feels like a neutral drop. I do not perceive that the transmission is slipping until the sudden engagement.

I changed the filter and fluid at around 60,000mi and the pan was very clean with tiny trace of material on the magnet. It has never run low on fluid. It has never thrown a code. It seems to shift fine through the gears without slipping. It only happens on take off after coming to a stop.

I would appreciate any thoughts. It has me stumped...

There is a TSB on this concern to replace the 2nd clutch plates and sealing rings. TSB #06-07-30-023E for the 4T65E trans.

Thank you GMTECH for your response. I looked at the TSB you suggested but do not think that it fits. The 1-2shift works well on this vehicle. The "slip occurs from idle as if the transmission is partially engaged then grabs a few feet after it starts moving. This occurs before the 1-2 shift.

Another thing I thought of that might be associated with this issue is that when the car comes to a stop there is an audible click as the transmission shifts down to 1st. The harder I brake the louder the click and under heavy braking I can feel it downshift. This might be normal for this transmission but it seems to me it should be smoother than it is. This click is consistent, not intermittent like the first issue I mentioned.

Thank you.

A internal trans problem will be very difficult to diagnose on this forum, my suggestion is to take the car to a qualified trans repair shop and have them take a look at it.

what could be occuring is you come to a stop but the transmission is stuck in 2nd gear. this may be just a solenoid replacement .

with these transmissions you must use the new dexron VI fluid do not use DEXRON III.

GM had many warrantee failures because of this. also owners of these vehicles had the fluid transfer done to remove all of the dexron III fluid.

not to be confused with the power flushing of the fluid which is not recommended.

Bad pressure control solenoid would do this.......you are slowing down as you approach a red light.....before a complete stop, the light goes green and you start to accelerate......the vehicle lurches/slips and then is normal driving....this is usually accompanied by a P1811 code...

UPDATE...

After driving the Impala for another 20,000 miles the problem became more regular and I could tell it was shifting slower than it used to. (still no code)

I decided to take the side cover off and replace the two shift solenoids, the TCC solenoid, EPC solenoid and the pressure manifold switch. (found the whole AC Delco set on Ebay for $95) While apart I changed the filter and flushed out the old Dexron III fluid and replaced it with Dexron IV.

I have been driving it for a few weeks now. It has not acted up and it shifts like a new one.

Thank you all for your advice....

What is the "EPC" solenoid I would have to agree with techll about the PCS solenoid.

UPDATE...

After driving the Impala for another 20,000 miles the problem became more regular and I could tell it was shifting slower than it used to. (still no code)

I decided to take the side cover off and replace the two shift solenoids, the TCC solenoid, EPC solenoid and the pressure manifold switch. (found the whole AC Delco set on Ebay for $95) While apart I changed the filter and flushed out the old Dexron III fluid and replaced it with Dexron IV.

I have been driving it for a few weeks now. It has not acted up and it shifts like a new one.

Thank you all for your advice....

it is a common problem this dexron III fluid. even with your low miles and the fluid changes you did prior to this issue it still did the damage on the valves. many have suffered from this bad fluid . dexron VI should continue to work but I would do the fluid change again just to be sure the old fluid is greatly reduced.

I have been researching like crazy to find a solution, I stumbled upon this and I hope someone can help. I have a 2005 chevy impala with the p1811 code. Driving uphill is a pain I will be cruising at 60 mph and once I start going uphill the mph goes down to about 40 and I have to really give it gas to make it go. I have changed the catalytic converter, new plugs, wires, fuel filter. All made a difference from when I first bought it. I have a shift kit in the garage but I'm not sure if installing it will help.