Sound upon engaging into 2nd gear (manual transmission)

[xybaby]

It is 2002 Saturn SL manual transmission, 91K miles. The car drives OK with no issue. The wheels are not well balanced. There are noise and vibration if you brake the car.

My main question is the transmission. This issue has been around for 4-5 months. If you go slightly high RPM in the first gear then switch to the 2nd, you can hear an unusual metal-to-metal sound. It is not loud, but this does not happen on other gears as well as the reverse. If you are gentle in the 1st gear, you can avoid this sound. There is no issue or resistance on the gear switching. The 2nd gear is as easy as others.

I am curious what can cause this clunk sound. Does it sound like transmission?

[toggenburg]

Most likely the second gear synchro is bad.
And if so, then everytime you hear that noise, some small metal chip is shearing off.

What about the brakes, have you have looked at them yet?

If it is the front pads, sounds like they are shot and you are hitting metal on metal> plus you need the wheels balanced to keep correct steering control on most any type of roadway.

[Walkop]

If you want to protect the gear while you investigate, I'd suggest shifting from 1st-3rd. Just rev a bit higher. It's doable, and won't damage anything. Just hold your clutch longer before releasing so your RPMs drop before shifting into 3rd.

However, question. Are you rev-matching when you downshift? You should hold the clutch until your engine RPM lines up with the RPM it will settle at when you release the clutch. The same thing goes for downshifting, except you press the throttle when you engage the clutch to raise RPM.

The sound may be caused by damage to internals exaggerated by slightly improper shifting.

[xybaby]

To me, it sounds not like synchro. But I am no expert. The engagement in 2nd gear is always smooth with no resistance. Maybe I should describe the sound better. It is not really a metal to metal high tone. It is more like a low pitch sound. You can feel there is a slight vibration or component movement underneath your foot.

Originally Posted by toggenburg

Most likely the second gear synchro is bad.
And if so, then everytime you hear that noise, some small metal chip is shearing off.

What about the brakes, have you have looked at them yet?

If it is the front pads, sounds like they are shot and you are hitting metal on metal> plus you need the wheels balanced to keep correct steering control on most any type of roadway.

[xybaby]

Now I guess I know how to best describe the sound. I played with the shift a lot yesterday. In the 1st gear, when the car is at 2500+ RPM, a quick shift to 2nd gear gives a clunk sound. However, if the car is below 2000RPM in the 1st gear, there is no sound. Other than the sound in 2nd gear, the car shifts smoothly with no issue.

Could this be Synchro, or transmission mount, or others? Thank you for the help!

[OldNuc]

I would be checking all your mounts. One is probably shot. There are 4 of them.

[xybaby]

I checked 3 mounts: top motor mount, transmission mount, transmission side dog bone. I do not see anything obviously wrong with those mounts. Please see the pictures of the transmission mount and transmission side dog bone below. I did not see cracks on the rubber. They all look good. I need to check motor side dog bone. I just did not have time to take the other wheel off today.

I have another weird observation. If I do the same gear shift while turning the car, I do not hear the clunking sound from the car. It only happens when car is moving straight.

Originally Posted by OldNuc

I would be checking all your mounts. One is probably shot. There are 4 of them.

[xybaby]

Can anyone tell me how to identify a bad tranny mount, dog bone mount or motor mount? I am no expert on it.

I also found I can stop that clunk by slowly release the clutch or slightly giving gas while releasing the clutch.

Many thanks!

Originally Posted by xybaby

I checked 3 mounts: top motor mount, transmission mount, transmission side dog bone. I do not see anything obviously wrong with those mounts. Please see the pictures of the transmission mount and transmission side dog bone below. I did not see cracks on the rubber. They all look good. I need to check motor side dog bone. I just did not have time to take the other wheel off today.

I have another weird observation. If I do the same gear shift while turning the car, I do not hear the clunking sound from the car. It only happens when car is moving straight.

[trottida]

Typically inspecting the rubber condition is what you're looking at. For the top mount you should not be able to place a pencil between the top of the rubber and the metal above and there should be no cracks. The lower trans mount is more subjective; if it's OEM and over 10 years old it's likely lost its effectiveness. The 2 dogbones will show signs of damage either in the rubber or the metal breaks.

If you're confident in the condition of your engine/trans mounts you may want to check the fasteners that hold them in place.

Check that the 3 nuts on the top motor mount are tight. I chased a clunk noise in my SL1 MT for a while until I noticed that the nuts had lost their torque (or were not torqued properly) and the mount was moving when releasing the clutch. This approach could be applied to the other 3 mounts too.

[xybaby]

Thanks a lot. I will definitely check. Sometimes, it is so annoying to have those sounds when the car feels so nicely when driving.

Originally Posted by trottida

Typically inspecting the rubber condition is what you're looking at. For the top mount you should not be able to place a pencil between the top of the rubber and the metal above and there should be no cracks. The lower trans mount is more subjective; if it's OEM and over 10 years old it's likely lost its effectiveness. The 2 dogbones will show signs of damage either in the rubber or the metal breaks.

If you're confident in the condition of your engine/trans mounts you may want to check the fasteners that hold them in place.

Check that the 3 nuts on the top motor mount are tight. I chased a clunk noise in my SL1 MT for a while until I noticed that the nuts had lost their torque (or were not torqued properly) and the mount was moving when releasing the clutch. This approach could be applied to the other 3 mounts too.

[xybaby]

I will replace the transmission side dog bone mount and transaxle mount.

Can anyone verify the following torque spec is correct?

Two bolts on dog bone mount: 52 ft-lb
Two bolts on transaxle mount to transmission: 24 ft-lb
One nut underneath the transaxle mount: 37 ft-lb.

[OldNuc]

The 2 bolts on dogbone are both 52ft-lb on the gen 3. The others are also correct.

[xybaby]

I replaced transmission mount with aftermarket Duralast brand. The car starts to show vibration. Is it because the new mount has bad quality? The outdoor temperature is below freezing here.

My motor mount was replaced 3 years ago also with an aftermarket version Westar. It passes pen test. Should I also replace this one again?

Originally Posted by OldNuc

The 2 bolts on dogbone are both 52ft-lb on the gen 3. The others are also correct.

[OldNuc]

Aftermarket top and trans mounts are crap to varying degrees. They have a very short service life as well. Try and find a top mount that looks like the solid face OEM mount. New properly installed dogbones tend to prolong the service life of the trans and top mount.