GM Ecotec idle and clunky F23 Getrag

Synchros shot? Weird noises while shifting? Not sure what needs to be replaced?
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trail rated
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GM Ecotec idle and clunky F23 Getrag

Post by trail rated »

Hello, I have a 2006 Saturn Ion 2.2L I4 equipped with a Getrag F23 M86/M94 manual gearbox.

There are a few issues that I am experiencing with my car and I want to know whether these things are normal or not.

1) It seems like there is excess gear lash which is causing a normally quiet clunk while shifting, operating the clutch while in neutral, or when engine power is removed and reapplied while in gear.

Once scenario where the clunks are prominent is when I accelerate out of a turn. If there is a lot of traffic, I would usually heal-toe into 3rd gear at 20-25 MPH, slow down to 12-17 MPH during the turn, and then accelerate out of the turn with the engine speed at 900-1300 RPM. If I push on the accelerator gently trying to preload the gears, there would be either two or three quiet clunks accompanied with a very small amount of bucking. If I am more aggressive with the accelerator I would get a loud single clunk. This doesn't happen at higher engine speeds.

2) While accelerating or decelerating at 1500-1800 RPM, there seems to be gear rattle. This car does not have a DMF so this may be normal.

3a) Usually I get rev hang (which I prefer), but if the temperature outside is high and the air con is set to outside air on a high fan speed, the engine speed drops very quickly between shifts. I have to tap the accelerator once or twice between up shifts in order to properly rev match. This car has a variable displacement compressor, so the higher the sensible and latent load on the system, the more power the compressor will pull.

3b) If conditions are the same as 3a, if I clutch in while stopping in 1st or 2nd gear, the engine speed will momentarily drop down to 500 RPM. At this point, the compressor will shut off and the engine speed will instantly jump up to the normal 800 RPM idle. Two or three seconds later the compressor will turn back on and everything will be normal until the same situation repeats.

4) If I try to make a fast start or try to engage the clutch aggressively, there seems to be some clutch shudder. Normally while starting from a stop, I would release the clutch pedal to the bite point and then do the see-saw to maintain 800 RPM. For moderate starts, I would release the clutch to bite point and do the same as on a normal start, but I would keep the engine speed at 1200 RPM. For fast starts (50%-60% into the accelerator), I would do the same as normal, but would keep the engine speed at 1500 RPM.

Fast starts make the car shake a bit while the clutch is slipping, but the same thing happens if I have to make a fast shift and end up slipping the clutch into the next gear instead of rev matching.

The dealer showed me TSBs saying that issues 1,2,3a, and 3b are normal for all GM cars, but I want to know if this really is typical of these cars. I purchased this car used 3 years back with only 34K miles and it was in very good shape. The car has 74K miles now and does not have a CEL or anything obviously wrong. I am a mechanical engineer and I like things to be smooth and consistent, so I am just a little annoyed by my cars behaviour. :lol: The gearboxes in my grandfather's 2000 UAZ 469 and 1976 ZIL-130 are both smoother running, though they are a pain to shift.

It is midnight where I am so I am sorry for any wording mistakes.
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Re: GM Ecotec idle and clunky F23 Getrag

Post by AHTOXA »

On ty first issue. Try second gear at those speeds rather than third. Clunk during bucking is normal.
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trail rated
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Re: GM Ecotec idle and clunky F23 Getrag

Post by trail rated »

AHTOXA wrote:On ty first issue. Try second gear at those speeds rather than third. Clunk during bucking is normal.
I do shift down to second gear if I have to accelerate faster than usual, and it is smooth, but 2nd is too low of a gear for normal (slow) acceleration.

This seems to have something to do with the DBW system. If I slow down to a stop, the engine will provide little engine braking above 1300 RPM. At 900-1300 RPM, my OBD2 scanner shows the throttle body fully closing and at that point I get serious engine braking. Once I tip slightly into the accelerator, the throttle body instantly goes from 0% to 18% IIRC. The fact that the ECM causes such a fast throttle increase is what seems to be causing the clunking.

This type of operation isn't going to cause damage, is it?
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Re: GM Ecotec idle and clunky F23 Getrag

Post by theholycow »

TPS readings through OBDII don't usually behave the way you expect them to, due to differences in the way it is measured, calculated, and reported. Going from 0% to 18% might be just 1% of the throttle's actual available travel. When it's at 0% you may be in DFCO; see if 0% correlates with open loop operation (the reporting latency of open/closed loop is usually quicker than most other data, so don't expect perfect correlation).

If you're not happy with your DBW's programming you may want to get a custom tune. Describe how you'd like it to behave and a good tuner should be able to program it for you.

To know if your issues are truly typical of your car, your best bet is to ask on a Saturn forum. There are few GM drivers here, I think there are zero Saturn drivers here, and I don't think anybody here has a GM from around 2006. My GMs are 1980 and 2002, both cable throttle, and both came with automatics (though the 1980 now has a manual).

My vague opinions on your specific issues, as un-helpful as these may be:

1. If your clunk is more severe than it should be just from going in and out of DFCO, check for broken motor mounts, clutch hub springs, CV joints, front-end suspension, and steering stuff.

2. Sorry, no idea.

3a and 3b. Rev hang vs. no rev hang is purely a matter of DBW programming (I guess unless it's acting on a faulty sensor reading somewhere). Instead of tapping the accelerator pedal, try just feathering it - slightly holding it down as if you wanted to hold a steady <however many RPM> in neutral in your driveway. Or, even better, drive the way people did before computers: Instead of consciously rev-matching halfway through the shift, just get on the accelerator pedal earlier during the shift - slightly before completing the shift instead of just after; like, around the time your left foot is about to come up, your right foot starts to go down.

4. Could be the clutch slipping (from wear, contamination, pressure plate spring failure, etc), could be common clutch chatter, could be wheel hop, could also be most of the things I suggested in my ideas for 1.

I was really expecting people who know more than I do to have responded by now, but there's my thoughts for now.
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Re: GM Ecotec idle and clunky F23 Getrag

Post by trail rated »

An interesting thing happened today. I service my own cars, and my neighbour asked me to look at his 2009 Honda Civic because of an idle issue. I drove the car around the block and even though the car was an automatic, if I would lift my foot quickly off of the accelerator while driving slowly with the A/C fan set to high, the engine speed would drop down to about 500 RPM before rising back to 800 RPM. This is exactly the same thing my car does. To resolve the issue, I cleaned the throttle body in the Honda and reset the ECM. This is the first thing I did to my car after I bought it, but it didn't make any difference in my case.

For a while I thought that the noise was caused by the way I was driving, but unless I was perfectly smooth with my shifts there would always be at least a quiet clunk. I did some searching around a while back and apparently there are people who do have similar issues as I have but there are also those that say everything is perfectly quiet and smooth.

To minimize noise and to provide smooth shifts, I bring the engine speed to within 200 RPM of where they should be in the gear that I selected, then for a split second I would press on the accelerator slightly while simultaneously holding the clutch at the upper part of the friction zone. After this, I would release the clutch completely while depressing the accelerator as normal.

I don't remember any of the MT cars that I drove making any noise, even if the shift was completely botched. Of course, all of those cars were 4WD/RWD.

People that ride with me don't notice any clunks and say that my shifting is as smooth as an automatic, perhaps my expectations for quietness and smoothness are set too high :?:
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Re: GM Ecotec idle and clunky F23 Getrag

Post by theholycow »

trail rated wrote:People that ride with me don't notice any clunks and say that my shifting is as smooth as an automatic, perhaps my expectations for quietness and smoothness are set too high :?:
This may be the most commonly posted statement on Standardshift.com.
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Re: GM Ecotec idle and clunky F23 Getrag

Post by six »

trail rated wrote:People that ride with me don't notice any clunks and say that my shifting is as smooth as an automatic, perhaps my expectations for quietness and smoothness are set too high
You only notice the clunks because you're looking for them and know exactly when to expect them. Your passengers don't, so they don't really notice because they aren't paying attention.
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Re: GM Ecotec idle and clunky F23 Getrag

Post by Squint »

theholycow wrote:
trail rated wrote:People that ride with me don't notice any clunks and say that my shifting is as smooth as an automatic, perhaps my expectations for quietness and smoothness are set too high :?:
This may be the most commonly posted statement on Standardshift.com.
Yeah. Next time you are in an automatic vehicle, watch people's heads bobble as the car shifts. It happens in almost every vehicle, except maybe CVTs. People don't notice because they are so used to having some movement when a shift happens, regardless of whether it's the car or a person.

Though you can always make it worse with a stick if you want to wake up your passengers. :lol: :lol:
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