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Anyone a transmission guru?


Buck531

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I have a few questions. Lately, when the converter locks up in my POS, the car vibrates. Sometimes a lot, sometimes a little. It kind of varies.

 

The trans was JUST rebuild probaby 2-4k miles ago back in October. New converter, (2500 stall), solenoids, etc.

 

It only does it when the converter locks up. In either 3rd, or 4th it does it.

 

Just wondering if anyone could give up a few minutes and take drive with me in the car and kind of get the feel for what it's doing since it's pretty hard to describe it over the net.

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Guest 78novaman

I know it sounds stupid, but just try this. We are talking about the lumina right?

 

The TC solenoid only locks up the torque converter in 3rd & OD. Whenver the brakes are pressed the computer automatically unlocks the converter. Get your car up to 45-55 mph and in 3rd gear or OD. When the vibration starts, keep on the gas to maintain a steady speed and lightly push on the brakes, dragging them on purpose. If the vibration goes away, then the TC lockup solenoid is fine. If it's still there, then I would take it back to the shop and complain until the problem is fixed. I seriously doubt its the converter or you would have major problems trying to accelerate in 1st.

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I know it sounds stupid, but just try this. We are talking about the lumina right?

 

The TC solenoid only locks up the torque converter in 3rd & OD. Whenver the brakes are pressed the computer automatically unlocks the converter. Get your car up to 45-55 mph and in 3rd gear or OD. When the vibration starts, keep on the gas to maintain a steady speed and lightly push on the brakes, dragging them on purpose. If the vibration goes away, then the TC lockup solenoid is fine. If it's still there, then I would take it back to the shop and complain until the problem is fixed. I seriously doubt its the converter or you would have major problems trying to accelerate in 1st.

 

Yep, it's in the Lumina.

 

Ok. I'll give the dragging the brake thing a try. If it stops doing it when dragging, any clue what it could be? Thing that sucks about the trans shop, it's 5 1/2 hours away from me. :(.

 

I've already ruled out an ignition/voltage issue. I've changed the plugs, wires, coil packs and it's still there. Changed the TPS sensor. Same.

 

What else could I check/change that's relatively cheap/easy to rule out things?

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Is it intermittent, at certain RPM's or constant in 3rd and 4th? Dampers are usually incorporated into the TCC, maybe the stall converters dont have dampers (save weight/cost/etc.). You might be hearing/feeling gear rattle in the drivetrain. The brake test is will give you a good indication if it is the TCC or not.
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It only started doing it under 2k rpm's. Within the past few months, it's gotten worse. Now it's doing it when the converter locks up in 3rd and in 4th between 1500 and 2200ish rpm's. Before, it would only do it when I put a slight load on the car when driving on the freeway (20% or so throttle). Now it's doing it when I set the cruise control anywhere between 60 and 70 mph.

 

I have a few auto tap scans if anyone wanted to look at it. TCC duty cycle, and every transmission part I can scan on it. If you want me to post them, let me know and I will. Not sure if it'll help anything out or not.

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Guest 78novaman

The quick fix is to pull the plug on the solenoid. It's usually a piece that screws in to the transmission on the front side of the car with a 2 prong connector attached to it. I don't know exactly where it is, but even a crappy haynes manual should have a pic of it. You can unplug this with no detrimental effect on the car or drivablity except about 5% reduction in fuel economy from higher RPM since the converter is not locked up on the highway.

 

I was drinking when I wrote my first response, re-reading it shows it's not as accurate as I hoped! I'm not drinking now so this should be better :)

 

A quick summery on the system: When you don't need the slipping of the converter to keep your engine from lugging or stalling, and to save some gas, a clutch was added to the torque converter that would lock it up in a 1:1 ratio so there is no parasitic losses. This clutch is activated by the ECM sending a signal to the Torque Converter Clutch (TCC) Solenoid. And as with any electro-mechanical device they go bad after time.

 

When you push on the brakes, or accelerate hard in 3rd or 4th, the TCC will be disengaged as to avoid lugging. Sometimes it even disengages the TCC when you let off the gas, as in luxury cars where you want a smooth ride. More sporty cars tend to leave the TCC engaged when you let off the gas, hence you decelerate faster, giving that stickshift sporty feeling.

 

If it's not too expensive, I would go ahead and replace the TCC solenoid first. Sometimes they get 'weak' (for lack of a better term) and cannot engage the clutch all the way to lock up the converter. This can create the vibrations that you are feeling. Also, the quality of replacement parts (especially electrical) is getting out of control. Get a good TCC solenoid from NAPA or a Chevy dealer and if it doesn't fix this then I'd go back to the trans shop. If they are reputable they should work with you to get it right.

 

Another option is a springs that would control the shift to 3rd & 4th have worn out/broken since the shop worked on the trans.

 

Also, does it feel like the transmission is slipping any at all?

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Nope. Trans doesn't slip at all, in any gear. It's solid and tight. It shifts perfect and crisp.

 

I'd rather not replaced the TCC solenoid. It's not fun to do (drop the cradle a little, pull the side cover off the trans, etc.). Something I'm not going to do.

 

I'm going ot be having another PCM coming my way here in a few days with the correct/added trans settings. A few people have already told me that it's a PCM related issue. We'll hope and see :). If it doesn't resolve it, I'll post back later this week.

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Nope. Trans doesn't slip at all, in any gear. It's solid and tight. It shifts perfect and crisp.

 

I'd rather not replaced the TCC solenoid. It's not fun to do (drop the cradle a little, pull the side cover off the trans, etc.). Something I'm not going to do.

 

I'm going ot be having another PCM coming my way here in a few days with the correct/added trans settings. A few people have already told me that it's a PCM related issue. We'll hope and see :). If it doesn't resolve it, I'll post back later this week.

 

If this doesn't work, try this. You'll have to trust me, although I'm pretty sure that Scott was going to offer the same suggestion. Automatic transmission seal conditioner.. GM # 12345837. Lord only knows what the hell is in this stuff, but it works. This stuff > * mechanic in a can.

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  • 2 weeks later...
If the PCM don't do it try the additve that was mentioned before it's a friction modifier, to make a long story short the fluid is to slick and the tcc clutch chatters, the additive takes care of this problem.

I told him this (his prob would have been solved by now)

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