Finally on the road....trans problems
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Joined: Mar 2012
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From: Elkridge MD
Will do, sir. I am in Elkridge not far from you. I'll keep you posted on my issue and please let me know if you solve it.
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From: Atlanta, Ga
Based on what you describe, I would be thinking converter. Fundamentally a torque converter is nothing more than a hydraulic clutch device. The fluid in the converter acts as the friction surface in a clutch disc. The impellers are the flywheel and pressure plate. Fluid "shears" to the stall point, then becomes static creating converter stall or lockup.
The more expensive converters hold tighter tolerances accounting for more precise stall ratings. Back in the old days some of the lesser converters were tuned with vise grips bending the impeller fins. The better units currently use stamped or even billet impellers manufactured for a specific purpose.
Converter stall is best expressed as the point which forward motion overcomes fluid shear. From a light float on flat ground, say 5-10 MPH with no throttle applied, mat the throttle and note the tach. The RPM at which you feel the forward surge is the converter stall. This will vary from car to car with the same converter based on vehicle weight, gearing, tire size and engine output. Rule of thumb, the more torque an engine produces, the higher a given converter will stall.
The next step would be to test fluid pressures at the pressure ports on the trans. That will give you a good idea of whether or not the pump is up to spec.
The more expensive converters hold tighter tolerances accounting for more precise stall ratings. Back in the old days some of the lesser converters were tuned with vise grips bending the impeller fins. The better units currently use stamped or even billet impellers manufactured for a specific purpose.
Converter stall is best expressed as the point which forward motion overcomes fluid shear. From a light float on flat ground, say 5-10 MPH with no throttle applied, mat the throttle and note the tach. The RPM at which you feel the forward surge is the converter stall. This will vary from car to car with the same converter based on vehicle weight, gearing, tire size and engine output. Rule of thumb, the more torque an engine produces, the higher a given converter will stall.
The next step would be to test fluid pressures at the pressure ports on the trans. That will give you a good idea of whether or not the pump is up to spec.
Something as simple as a cam (or gear) change can make a sloppy converter feel great or a great feeling converter drive terribly.
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From: Atlanta, Ga
Good point! The real lesson is that there is no magic silver bullet. In the past I have run everything from stock to switch pitch converters and full on race converters with a trans brake all on the street. The race converter was built by Hughes to flash stall at 4800 on the brake. It still was streetable enough to drive anywhere I wanted. The trade off was cost. That unit was $750.00 at cost with a very friendly buddy deal. I had them freshen it once each year just to be safe. In any case think about cooling, this is very important.
Ls lemans, the answer is not that simple and everyone has an opinion and the actual combination will guide you on the path. Rear gear ratio, engine output, tire size, cam specs, and your expectations. For a daily driver I am all about a stock 12" converter, flash stall about 1200 RPM. Economy, driveability and no worries about overheating, but this is just my opinion.
Ls lemans, the answer is not that simple and everyone has an opinion and the actual combination will guide you on the path. Rear gear ratio, engine output, tire size, cam specs, and your expectations. For a daily driver I am all about a stock 12" converter, flash stall about 1200 RPM. Economy, driveability and no worries about overheating, but this is just my opinion.
I don't know if you saw it, but Hackster is having some trans problems. There was some discussion about VSS and ISS sensors and maybe some plugs being switched up. Not sure if it's the same thing you are dealing with, but might be worth checking out.
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From: Elkridge MD
I found the thread and gave it a read. It seems like his issues are/were more extreme than mine, as mine drives "ok". he also switched over to a 4L80, which I think is the main issue for him. I don't believe the 4L60e has a separate ISS sensor, just the VSS at the rear passenger side of the trans....is the correct or no?
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From: Elkridge MD
Ok I discovered I had a very sneaky little leak at the dipstick tube. It wasn't coming out of the vent like I originally thought. I fixed the leak and then filled the transmission to the proper level (while hot, level and idling). I took the car around the neighborhood and there was definitely an improvement as far as getting power to the wheels. Hills still felt a little funny in my opinion but I could have been imagining it. It was CLEARLY much better though.
But now I notice a vibration/shudder under acceleration. It MAY be there when not accelerating, but if it's there I can't feel it (I have solid motor mounts, by the way).
While experiencing the vibration, I tried to tap the brakes a tiny bit to see if the TCC doodad would shut off or whatever. It did not affect the vibration at all. I tried this several times.
Driving the car at neighborhood speed, it seems fine, but it still feels like I should have more power than I am feeling.
So? Torque converter? TCC solenoid? Something else?
But now I notice a vibration/shudder under acceleration. It MAY be there when not accelerating, but if it's there I can't feel it (I have solid motor mounts, by the way).
While experiencing the vibration, I tried to tap the brakes a tiny bit to see if the TCC doodad would shut off or whatever. It did not affect the vibration at all. I tried this several times.
Driving the car at neighborhood speed, it seems fine, but it still feels like I should have more power than I am feeling.
So? Torque converter? TCC solenoid? Something else?
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From: Kansas City, MO
So you have a separate TCM on a 2000 4l60e? Is it a GM TCM or an aftermarket TCM? The 4l60e got its own ISS when they started using a separate TCM. Maybe your trans is shifting weird because it doesn't know the input speed since it's an older trans. The older trans used engine rpm as the ISS since it was the same module controlling the engine and trans. Also is it actually starting off in 1st? If there is no power to the trans connector it will default to 3rd gear since both shift solenoids are always off.
Thread Starter
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From: Elkridge MD
So you have a separate TCM on a 2000 4l60e? Is it a GM TCM or an aftermarket TCM? The 4l60e got its own ISS when they started using a separate TCM. Maybe your trans is shifting weird because it doesn't know the input speed since it's an older trans. The older trans used engine rpm as the ISS since it was the same module controlling the engine and trans. Also is it actually starting off in 1st? If there is no power to the trans connector it will default to 3rd gear since both shift solenoids are always off.
It's a separate TCM but it's the stock one from the GTO. So maybe I should look for a newer 4L60e? I will look under the car for an unused pigtail that should be going into an ISS sensor but I don't think I remember any begin there.
To be honest, I really can't tell if I am starting in 1st. I have never had this much horsepower under my foot so I can't really compare it to anything. Starting in 3rd though, that seems like it would bog down so hard that it would barely move.
Also, I don't think the older trans would be causing this vibration, so clearly there is something else not functioning properly
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From: Atlanta, Ga
Low fluid will cause sloppy shifts and a feeling of slippage. I don't think it is a TCC problem. Do you know if your trans has PWM lockup for the converter? Secondly do you know if your converter still has the lockup feature? Some builders delete the lockup clutch.
The transmission does not care which TMC or PCM you are using. The early red/blue or green/blue PCM contains the TCM. The later ECU(E40 style engine control unit) requires an separate TCM (trans controller) for the automatics. The 6L80/6L90 have a built in TCM. Mushy shifting or shifting too quickly is most likely a TCM issue. I can't see the trans starting out in 3rd. It could be starting in 2nd, if you see a DTC that throws it into limp home. The shudder you feel could be many things including the converter, drive shaft angle problem, headers hitting the trans cross member, loose mount or lots of other issues.
The transmission does not care which TMC or PCM you are using. The early red/blue or green/blue PCM contains the TCM. The later ECU(E40 style engine control unit) requires an separate TCM (trans controller) for the automatics. The 6L80/6L90 have a built in TCM. Mushy shifting or shifting too quickly is most likely a TCM issue. I can't see the trans starting out in 3rd. It could be starting in 2nd, if you see a DTC that throws it into limp home. The shudder you feel could be many things including the converter, drive shaft angle problem, headers hitting the trans cross member, loose mount or lots of other issues.
Thread Starter
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From: Elkridge MD
Low fluid will cause sloppy shifts and a feeling of slippage. I don't think it is a TCC problem. Do you know if your trans has PWM lockup for the converter? Secondly do you know if your converter still has the lockup feature? Some builders delete the lockup clutch.
The transmission does not care which TMC or PCM you are using. The early red/blue or green/blue PCM contains the TCM. The later ECU(E40 style engine control unit) requires an separate TCM (trans controller) for the automatics. The 6L80/6L90 have a built in TCM. Mushy shifting or shifting too quickly is most likely a TCM issue. I can't see the trans starting out in 3rd. It could be starting in 2nd, if you see a DTC that throws it into limp home. The shudder you feel could be many things including the converter, drive shaft angle problem, headers hitting the trans cross member, loose mount or lots of other issues.
The transmission does not care which TMC or PCM you are using. The early red/blue or green/blue PCM contains the TCM. The later ECU(E40 style engine control unit) requires an separate TCM (trans controller) for the automatics. The 6L80/6L90 have a built in TCM. Mushy shifting or shifting too quickly is most likely a TCM issue. I can't see the trans starting out in 3rd. It could be starting in 2nd, if you see a DTC that throws it into limp home. The shudder you feel could be many things including the converter, drive shaft angle problem, headers hitting the trans cross member, loose mount or lots of other issues.
I am also running the E40 computer and the separate TCM.
Headers/exhaust are definitely clear of the driveshaft and crossmember, and driveshaft is new and balanced. Everything seems to be bolted up tight too.
Driveshaft angle might be a problem, as I did raise the engine some and it is at a bit of an angle. Can this be corrected with adjustable upper control arms? Or is it something more elaborate to fix?
One thing I know for sure is that the shudder I am feeling was not present until the fluid level was corrected. I know it didn't do it before.