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Grinding noise coming from manual transmission in 3-5 gears?

edited September 2011 in Repair and Maintenance
Hello all, I have a 2007 Dodge Caliber manual transmission. When I shift the car (while driving) from 2nd into 3rd/4th/5th gear, I suddenly notice what sounds like a "grinding" noise that stays with the car while in those gears. It's clearly an abnormal noise and noticeable but not obnoxious. It does not occur in 1st or 2nd (although it seems that maybe at higher rpms in 2nd gear I begin to notice it coming, though maybe it's my imagination), but the second I shift to 3rd gear and give it gas, the noise shows up instantly. Now when I let my foot off the gas, the noise goes away 100%. The second I give it gas again, it comes back. Also I don't believe the noise increases or decreases in relation to the speed of the vehicle. It seems to stay constant no matter what speed I'm at, as long as I'm actively giving it gas.

It occurs every time I drive, but I don't notice any other weird noises or problems with the car and the clutch feels good. I haven't been able to find any leaking anywhere underneath the car. It has approx. 92,000 miles and is a 1.8 liter 4-cylinder. I've spoken with a few folks and I've been given the following ideas:

1) bad clutch/assembly (replace clutch kit)
2) bad throwout bearing
3) bad bearing inside transmission associated with 3rd,4th,5th gear rod (?)
4) low transmission oil, 3-5 gears not oiled enough and causing noise
5) maybe nothing to do with transmission at all?

Could some folks offer advice on those above options or any others? I plan on taking the transmission apart this week with a mechanically-inclined friend of mine and if I have a good idea of what it could be, that may save us a lot of time by not having to take unnecessary things apart (ie. tranny vs bellhousing). Thanks!
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Comments

  • Has the transmission fluid ever been changed? This SUV should have the transmission fluid changed every 48,000 miles according to Schedule B of the Owner's Manual, and requires ATF+4 fluid.

    I agree with all of those ideas except 5), and the simplest and cheapest to check is the fluid/lube level. Low fluid will cause gear noise, which is accelerating transmission wear.
  • Start with gear oil change with the factory recommended fluid. It could be clutch noise but a bad throwout bearing will show some change in the sound when you put some light pressure on the clutch petal.

    If the noise is coming from inside the transmission, things will deteriorate pretty fast. Gears are "hardened" which is on the outside of the teeth. Once you wear through the hardened material the gear will wear out quickly. Meaning more noise and eventually a total failure. Bearings can last a bit longer, but once badly worn the noise will get louder and the shaft the bearing supports can move and take out more parts of the transmission.

    I really don't know your mechanical skill, but I hope you have a lot of skill, a very good manual, or a knowledgeable friend it you break apart the transmission. Taking it apart is easy, putting it back together is a whole different story.
  • Does you mechanically inclined friend have experience taking apart and putting together modern manual transmissions? Do you have a nice clean shop with plenty of space?

    I disagree with Uncle Turbo on one point. He says they are easy to take apart. They are hard to take apart and a whole lot harder to put back together. When you take it apart, there are a lot of little pins and stuff that tends to fall out before you can catch them so you need a nice, clean, well lit shop so that you can find them. A sweep magnet might come in handy too.
  • Check for heat shield rattles on the exhaust system. This can be erratic in nature and may come across as a rattle, buzzing, or even be construed as a grinding sound. This is often mistaken for a transmission problem too.
    Wrap a rag around the end of the tailpipe and whale on the rag with a balled up fist or rubber mallet. If you hear a rattling sound then there's a strong possibility you are hearing a heat shield rattle.

    I think it's a big mistake to consider taking the transmission apart at this point in time.
    There's a lot more to disassembling and reassembling (knowing what to look for, special techniques or tools involved, etc) a manual transmission than you might think.
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