What are the signs of a manual transmission going bad?

My car makes a weird noise after engaging the clutch in first gear between 1000 and 2000 RPM. It only does it in first gear, between 1K and 2K. It's a slight noise, but it's noticable. It's almost like a grinding noise, but it isn't loud or obtrusive, I just notice little things like this. It sounds like the AC compressor does when you first turn it on. Is this just the way first gear sounds or am I in trouble? My car only has 64k miles on it and I havent really ragged the tranny out. If it is the tranny going bad then my confidence in Nissan reliablility is going down the drain. If you need more info, let me know and I'll do what I can. Thanks!

 

First gear should be smooth and quiet, with perhaps a low volume "singing". No grinding.

The typical symptoms of impending 5-speed transmission failure include ...
- consistent ugly grinding when shifting into a particular gear
- the stick "fights you" when shifting
- a loud humming droning sound
- a tendency to pop out of gear on its own

I'm not convinced the sound which has you worried is even coming from inside the tranny. The heat shields on the exhaust system sometimes become loose and make a variety of humming, buzzing, rattling sounds. Please check those shields.

You could change the transaxle gear lube. This would be done as a diagnostic measure, not a remedial one. Watch the lube as it drains out. If it is brown or black, that is okay. If it is shiny and silvery, that is a bad sign because the silver color comes from thousands of tiny metal fragments. You can do this in your own driveway for less than $10.

 

First of all, thank you for you expertise. You just saved me a "diagnostic fee" at the dealership. I just had my car serviced for 60K a few months ago, so I'm sure the fluid is fine. I will go check the heat shields, however I do not think that is it because it only makes this noise in first gear from 1k to 2kRPM. Also, my car doesn't experience any of the symptoms you listed for impending transmission failure, with the exception of the shifter feeling a bit notchy when engine is cold, which I'm told is normal. And when you say first gear should "sing", could you elaborate a little if possible; that may very well be what I'm hearing. I'm not talking about the normal first gear "whine". Also, I only hear this noise between 1 and 2K, if that makes any difference. Thank you for your information!

 

If there really was a defect the sound would probably increase in intensity as RPM increases, not go away at 2K RPM.

Notchy when cold is normal. Some Maxima owners report that synthetic gear lube eliminates that behavior. My Maxima is still running on the factory fill.

I'm referring to "whine". It's difficult to describe mechanical sounds in words. Normal 5-speed gear whine is (to my ears, anyway) barely noticeable. The sound is pleasant rather than disturbing.

Mechanical sounds which are heard only at a specific RPM or RPM range are often sympathetic vibrations. This is true of all vehicle sounds, not only transmission sounds. You might check your shifter and linkage for looseness.

A low-volume sound may seem to go away above a certain RPM when, in fact, it is simply drowned out by other normal sounds. It is difficult to distinguish between these two situations. Here's an experiment you could make, if you can find a safe place to do it. You need a gentle downgrade in a quiet area. Drive at 10 mph in 1st gear, roll down the windows, step on the clutch, and switch the ignition OFF. This eliminates engine sounds and allows you to hear all other vehicle sounds more clearly. Keeping the clutch pedal "floored" you can shift through all forward speeds and compare the sounds. This experiment might confirm your fears about transmission noise, or it might reveal that your unwanted noise is actually coming from a brake or wheel bearing.

 

Tommorow I have an appointment at the dealership. You mentioned that it could be a wheel bearing. What exactly is that? MY dad rode in the car with me and thinks it is something along those lines, possibly a CV boot. I really do not think it is the transmission, as the car is only 4 years old, and the tranny performs fine. But if it were the transmission failing, about how much would that cost to replace? Thanks.

 

From that SH!Thole that I took my 92 to it cost me $1500 for a rebuild, I would say that you will be looking at about $4000 for a brandnew one from the dealer, my 92 tranny new from the dealer was $2000.

 

It is time for you to make a sincere effort to educate yourself. I must suggest, tactfully, that you read a repair manual. Chilton is good, Haynes is better. You can buy these books in any large bookstore or auto parts store. They may be available at your public library.

There is no crisp answer to this kind of question. In many instances a damaged transmission can be repaired for less money than installing a replacement.

If a replacement were truly necessary you would probably choose a used unit from an auto recycler. The cost of used parts is dictated by supply and demand and will vary quite a bit from place to place and season to season. If it is important for you to know the price, open your Yellow Pages and get on the phone. Figure the replacement cost would be the cost of the used tranny plus $200-$300 labor.