99 Lumina LTZ Transmission Shifts Rough

Just purchased car. Seems when cool, everthing is fine. After warms up, the car shakes hard when it shifts... sometimes. Kinda like a wheel hop. It is really bad if I accelerate hard. Sometimes is does it when accelerating normal. Sometimes it is fine. A light comes on dashboard when I start the car. Say "low trac", and then goes off. I do not know if that has anything to do with it. Light doesnt come on when the problem occurs. Where should I start?

The 1999 Lumina LTZ uses the GM 4T65E Hydramatic transmission.
Your problem is probably the Pressure Control Solenoid not working to its design standard.
You need to have a technician pull the Data Codes to see just what the problem is. The Transmission has its own Micropressor and works with the Engine Computer to do its thing.
If you have 2 or more drivers in the family, the learning curve will never set up and remain standard.
My LTZ does the same thing occasionally but it doesn`t shudder or slip.
I just pull over, shut off the engine for 3 minutes and restart- it works fine for months . It has occured on my car about 6 times in 5 years and I baby my car. If you experience hard shifting -do not mash the gas and go thru the gears like a maniac or you will create additional problems.
Get your codes pulled and fluid/ filter changed and you shpuld be OK.
The cause of the hard shifting is too much line pressure relative to the throttle position. This is an ongoing problem with GM transmissions- they never seem to get it right. The transmissions are built by Union workers and the parts are bought by Bean Counters. The Lumina is great car (for me) My 2nd one and this has 98,000 miles now. No breakdowns yet.
Bob

I have a 2001 Chevrolet Lumina Sedan, not LTZ, or LS, and when i first purchased it, it had 39,000 miles on it, and it was going that same thing for me. The tranny would kinda jump, or jerk before it locked into 2nd, mainly under hard acceleration, and sometimes normal. I just rode it out. I said, damnit if the tranny is going in this new car, I cant believe it, and wouldnt you know it, a month later, it shifts as smoothly as any new car should. As for the LOW TRAC light, thats just normal to come on too. Its just your ECM going through its startup diagnostics. Good luck with it. I would however have the tranny fluid flushed. Or maybe just check it. Drive your car normally for about a hour, and stop, leave it running in park, and pull the tranny dipstick, and check it much like you check your oil. If its red, your in the clear. If its black, and has a funky smell to it, say goodbye to your beloved car, and sell it before a new tranny is needed. And FYI, average milage between tranny flushes is about 40,000 miles.

I have had previous experience with Lumina Tanny's. If you have any warranty from where you bought it, then by all means take it back. If you don't and you are on a tight budget like me, do a tranny filter and fluid change and go from there. YOur tranny will also shoot a code to your computer and your engine service light will illuminate. This filter and fluid change is inexpensive and a good place to start, escpeacially if you don't know the history on the car. Good luck:)

I get a wierd kinda double thud harsh shift every now and then from mine, as if it decided in mid-shift to change its' mind. Its been like that since it was new. I ignore it. When it happens, it feels like the older ones felt when the roll-restrictors were broken. Like the drivetrain is pitching back and forth rapidly, rebounding from the shift. But it is not. The mounts are all solid. I'm not worried. Did the first tranny service at 112,000, all was good. Minor fluid discoloration and minimal debris in pan.

I don't know if this is related but...

I have a 3.8L Lumina that occasionally shudders when I step on the gas, after putting it in gear. It doesn't happen regularly -- just out of the blue, for no reason, when I'm doing a lot of delivery driving.

What happens is I'll start the car, shift into drive, step on the gas and the car won't move forward much, but instead the engine shudder violently and make some ungodly noises. The only thing I can compare the shudder to is when I once accidentally put spark plug wires in the on the wrong plugs, screwing up the firing sequence(on a different car though). This shudder lasts 1-2 seconds and then the car runs fine.

I think the car may have done this once before I shifted into drive, which makes me believe it may not be the tranny. It may be just wishful thinking though.

I have a constant service engine light on because of some gas fume evaporation system malfunction that I don't really care enough about to fix right now(yes, I've changed the gas cap and it is tight), so I don't know if there were any new codes sent.

Could this be the crankshaft position sensor or an intermittently bad injector? Or is it a solenoid not putting the car into gear in time before I accelerate(I've been waiting a few seconds after shifting into drive and it hasn't happened since)?

It could be you have a bad mount, and when you try to drive away before the motor has "torqued over" against the slop, It pitches the motor suddenly, and you feel the shudder and hear the impact. Try putting it in gear with the hood up, and watch what happens when you hold the brake firmly and give it gas in gear. If a mount is broken, you will see the motor pitch over hard, and may hear a thud along with it.

All these trans concerns are very common and sound like a falty pcs. The pcs is macanicly binding causeing a decrease in psi and causeing the trans to shudder on accel. I would take it to the dealer for proper dia........

New Problem:

Car runs fine for about five minutes, then when the tranny shifts, I feel a bit of a thud. Kinda like when you're driving stick and you pop the clutch too fast. When it goes into second gear, there's a buzzing sound.

If I let the car sit for a few minutes, the problem goes away, then starts up again after five minutes.

I'm not getting a service engine light either. Are certain tranny fault codes stored even though they don't illuminate the service light?

I should also add that there are metal filings in my fluid, but the fluid is the good red colour.

New Problem:

Car runs fine for about five minutes, then when the tranny shifts, I feel a bit of a thud. Kinda like when you're driving stick and you pop the clutch too fast. When it goes into second gear, there's a buzzing sound.

If I let the car sit for a few minutes, the problem goes away, then starts up again after five minutes.

I'm not getting a service engine light either. Are certain tranny fault codes stored even though they don't illuminate the service light?

You have a very common transmission problem with your Lumina.
The hard shifting and buzzing noise is caused by the PCS or Pressure Control Solenoid inside the transmission calling for maximum line pressure to the hydraulic circuit. The buzzing noise is the pump itself working very hard to reach maximum pressure.
The high pressure within the transmission is harmful if allowed to continue day after day. The DTC data code for a bad PCS is P 01811.
If you get this code- you are in deep doodoo. The transmission repair shop will pull the code for 69.00 and change the fluid.
The Big Dogs at General Motors do not admit a design failure with the 4T65E Hydramatic transmission and they claim the problem to be the PCS in 6 out of 10 times. The other 4 times are caused by the clutch discs being worn out.
The PCS must be changed with the transmission OUT of the car- this is big bucks to have it done. A new or rebuilt transmission is the only way to go at the tune of iover 2,000.00 greenbacks.
My suggestion is to dump the Lumina and Buy ANY foreign car.
I had 2 different brand new Luminas and both of them done the same thing as yours early on in their life. NO more GM cars for me.

Ouch, looks like you Lumina owners are no better off than us Century owners. I was browsing the forums with vehicles which I knew had the 4T65E transmission to see if other vehicles had the same problem. Sure enough.

Yes, you most likely have a bad PC Solenoid Valve. I had mine replaced to the tune of $615.00 (fortunately I bought an extended warranty), HOWEVER the problem persists. The car no longer goes into limp-home mode, but it still shifts harshly and shudders, especially once the engine has warmed up. I've now heard several possibilities -- clutch discs, bad PCM, bad grounds. I'm taking the car to my mechanic (NOT the dealer which performed the work, they still refuse to work on the car since it is not "throwing" any codes) to see what he thinks.

If you want more specific info about mine and other Century owners, head over to the Century forums -- we are all experiencing the EXACT same problems.