engine and drivetrain sot: help me diagnose the sound into my transmission

[PatAllen]

I need to diagnose the sound before taking it off, to the best i can.

Its into my E36.

How can i differentiate the sound of bad gear versus bad bearings ?

Dont tell me its the pilot bearing. Its not. The transmission makes noise when the car is at rest or in movement, so the input shaft is coupled to the engine and the pilot bearing dont turn. It just hold the shaft, the clutch is holding it too.

Noise disapear when i press the clutch so the input shaft stop to rotate. Its at this moment that the pilot bearing "works". No noise then.

I know the input shaft has some play in it. I dont want to assume it is only the bearings that causes the noise.

My question would be if the layshaft is always coupled to the input shaft, if yes that means the gears could be worn as well and the noise could come from this set too.

The overall noise when i accelerated is quite high pitch. It is a function of engine speed, not car speed. It disapear at around 3krpm.

When i shift at low speed i can hear the input shaft reaching the new gear speed before engaging the clutch.

Id prefer to be able to rebuild this transmission rather than installing an suposedely good one. Every one knows that guys into scap yards says they had them verified, just like if they were able to do something magic that we cannot do, do they open them to measure clearances,... ??

surely not.

Input shaft for this transmission is around 500$ and the layshaft too...

thanks for any inputs

[jgerry2002]

Im not sure I've ever had a bad gear in a tranny that did not pop out of gear or make horrible crunching sounds.

Bearings can hum/rattle a little at idle, but I've never heard of anything in gear except the occasional "grumbling" sound when lifting off the throttle.

This can be from worn engine mounts (have these been replaced ever?), bad guibo, or worn tranny mounts (I assume you've replaced these?) throwing everything out of alignment.

[PatAllen]

Im not sure I've ever had a bad gear in a tranny that did not pop out of gear or make horrible crunching sounds.

Bearings can hum/rattle a little at idle, but I've never heard of anything in gear except the occasional "grumbling" sound when lifting off the throttle.

This can be from worn engine mounts (have these been replaced ever?), bad guibo, or worn tranny mounts (I assume you've replaced these?) throwing everything out of alignment.

no no, the sound is realy into the transmission, nowhere else. alignement of what, it makes it when the car is at rest and idling. i could in fact disconnect the entire driveline and it will still make it.

the input shaft always make rotate the layshaft per my understanding of this transmission, but i cannot confirm. if that is true then this gear set is not associated to a "speed" gear, just a transfer motion to the layshaft.

the picture shows the input shaft and the layshaft gear set. theses two presumably always rotate no matter the selected gear.

[TobyB]

yes, the coutnershaft is always coupled to the input shaft.

From what you describe, it's most likely the countershaft bearing, and they

usually go on the input side, nearest 1st, since that has the most stress on it.

But given that it's so much labor to get everything apart, I always replace

the main bearings and c-shaft bearings together. And usually 2nd and 3rd sychros,

just because, after all that work, I want the trans to actually feel better!

Like I got something for my time and money!

hth,

t

[PatAllen]

yes, the coutnershaft is always coupled to the input shaft.

From what you describe, it's most likely the countershaft bearing, and they

usually go on the input side, nearest 1st, since that has the most stress on it.

But given that it's so much labor to get everything apart, I always replace

the main bearings and c-shaft bearings together. And usually 2nd and 3rd sychros,

just because, after all that work, I want the trans to actually feel better!

Like I got something for my time and money!

hth,

t

would you pretend that i could get away by just changing the bearings ?

my fear is that the gear set that couple the countershaft to the input shaft are toast as well, hence my question how in the hell can i differentiate bearing noise from gear noise...it could be both as well, ohh, yeah...

i am looking at the bmw tiscenternet diagrams right now...it dont look that bad to open a s5d250. I opened several other transmission in the past, 4 speed from 02 and my 5 speed overdrive to mention two bmw ones.

argh.

[Arshloch]

input shaft bearing makes noise all the time, especially pronounced at idle. The layshaft bearing may not even be noticeable in overdrive, hence, tendency for it to go away.

don't think you can get away with replacement of the suspected bearing only.

[allbim]

If you are going to pull the tranny apart, you might as well replace all the bearings in it. They are not that expensive. And while you're at it, replace the synchro rings.

It has been my experience that worn (pitted) gears make a loud knocking or clicking noise when you are on the throttle. It is usually one tooth that gets pitted first. I think your bearings are bad, not your gears. The most reasonable price for synchro rings(about $50.00 a piece)I have found so far is at this link.

http://www.wallothnesch.com/index.htm

[PatAllen]

If you are going to pull the tranny apart, you might as well replace all the bearings in it. They are not that expensive. And while you're at it, replace the synchro rings.

It has been my experience that worn (pitted) gears make a loud knocking or clicking noise when you are on the throttle. It is usually one tooth that gets pitted first. I think your bearings are bad, not you gears. The most reasonable price for synchro rings(about $50.00 a piece)I have found so far is at this link.

http://www.wallothnesch.com/index.htm

thanks, i am still trying to source a good used trans that at least i can check before, ie, input shaft play, i can still put a drill on it and make it rotate so i can hear if there is any suspicious noises...

anyway...i am so unlucky with that car, i wouldnt be surprised to get another trany and it would be worst...