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240 Ideas? Loud Transmission in every gear except 4 (5spd manual)

boxing_day

New member
Joined
Mar 12, 2016
Location
Maryland
I'm a proud new owner of a 91' 240 wagon with 5 speed manual. I noticed that all the gears seem to have a relatively loud mechanical noise, sort of like the louder humming that comes from the reverse gear in many manual cars- just like loud gearbox noise. I might not have noticed or thought much about it since the sound doesn't sound bad or wrong, just a bit loud. The reason I noticed though is that all the gears seem to have this louder sound, except 4th which is relatively quiet in comparison. Thinking back to the 78' 242 with 4speed manual I sold a few years ago, I'm thinking my current gearbox is quite a bit louder than that one was. In that car, I remember engine noise being louder than transmission, but in this car it's the reverse.

Any thoughts on this- is it normal or is it something to be concerned about? Anything I should do or check? It's a relatively small annoyance, but if its a simple fix or a big problem, I want to know about it.
 
It probably has some wear going on from being low on oil. Might be a good idea to do the overfill trick. Put the left side of the car up on ramps and fill the trans with two quarts of oil. That will raise the level a bit over the standard fill but not so much that it leaks out of the vent. Maybe a bit of something like moly slip to help compensate from the wear.

When the trans wore out in my 93 wagon it started with just third being noisy. But after another 50k miles or so it had worn to making a gravely noise in all gears except fourth. But that was with about 325k miles when third got loud and then by 286k I had complete failure happening.
 
The reason it is quieter in 4th gear is the power is not being transmitted through the cluster gear. 4th gear just locks the input shaft to the output shaft, direct drive. No load on the cluster gear. It is just going along for the ride. That may indicate worn cluster gear bearings.
 
Helpful. Would adding more oil help quiet it down, or is that going to be something I have to live with now that it's worn down?

This car has a little over 150k miles so far lower miles than what you're talking about. With regards to changing those bearings, is that a doable job or not worth it? I've been doing some reading and many say its often cheaper/easier to just outright replace the trans (even though they can be hard to find...
 
Overfilling the transmission will probably muffle the noise a bit. It isn't going to help lubrication properties in any way.

I'm reading that some say to use 10-30 motor oil in the transmission because it's a bit thicker and can help out worn gears. Good idea or should I use something else?
 
It will eventually fail, but with more frequent oil changes, it could still live for years. Its maybe a good idea to fill each drained old oil into clean plastic bottles, so you can see how its condition getting worse. Overfilling won't cure the worn bearings, won't really make it last longer, but you won't do anything bad with adding a few deciliters more. My vote is 75W, GL4 manual transmission oil.
 
It will eventually fail, but with more frequent oil changes, it could still live for years. Its maybe a good idea to fill each drained old oil into clean plastic bottles, so you can see how its condition getting worse. Overfilling won't cure the worn bearings, won't really make it last longer, but you won't do anything bad with adding a few deciliters more. My vote is 75W, GL4 manual transmission oil.

Makes sense. Can the bearings be replaced? I assume if it's possible, its a big job...
 
If you are going to take apart the trans to replace bearings. It's the time to rebuild the trans. Since it's still working. It may be less to rebuild than one that has failed. It won't be cheap as parts for these trannys are expensive but it is nice if you plan on keeping the car for a long time. Then you will get your value back by putting your miles on it.
 
It can be rebuilt, but it needs a few special bits... I'm about to put together my second M47, now with proper shimming and glued in bearings.
There are two bearings of the six which you cant buy anywhere as i experienced. Input shaft 6306NR C4 and counter shaft front RNU205 special snapringed bearing. Fortunately you may only need the last one, and with a skillful lathe guy it can be converted to accept the snapring. Countershaft two tapered rollers are standard inch sized bearings. Output shaft 6306ZNR C3 is more or less a standard one, output shaft roller bearing can be bought from volvo on 3 different part numbers. You also need a special bearing puller for the output shaft 6306...
 
The input shaft bearing is still available from Volvo.

https://www.tascaparts.com/oem-parts/volvo-ball-bearing-1377098

I have most of the parts to rebuild an M47 in stock. I ordered the NLA cluster (countershaft) bearing from Russia last month and I'm still waiting for it to arrive.

JP4I5oCE4t73VADZ
 
The input shaft bearing is still available from Volvo.

https://www.tascaparts.com/oem-parts/volvo-ball-bearing-1377098

I have most of the parts to rebuild an M47 in stock. I ordered the NLA cluster (countershaft) bearing from Russia last month and I'm still waiting for it to arrive.

JP4I5oCE4t73VADZ

Oh sorry, i was wrong! It was a year ago when I ordered one piece of 183827 bearing for the output shaft (because the input shaft bearing looked fresh, but the output shaft bearing... now i remember clearly), and got a plain cheap chinese crap in a fancy and expensive volvo box:
<a data-flickr-embed="true" href="https://www.flickr.com/photos/97357313@N06/49909915853/in/photostream/" title="20190508_094056"><img src="https://live.staticflickr.com/65535/49909915853_134ee0fb04_b.jpg" width="1024" height="576" alt="20190508_094056"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>

I'd like to see a picture of that input shaft bearing, is it really a big balled ZNR C4 with plastic ball cage...

Anyway, at that time i asked a buddy to machine a groove in my new skf NU205 bearing, so its definitely doable:
<a data-flickr-embed="true" href="https://www.flickr.com/photos/97357313@N06/33712566318/in/dateposted/" title="received_561315230943843"><img src="https://live.staticflickr.com/7825/33712566318_617041d71e_b.jpg" width="562" height="1000" alt="received_561315230943843"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>
 
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