Dogleg Gearbox Rattle

[Balame]

Hi guys,

I got an M535i with the dogleg gearbox. Currently experiencing a rattle noise from the transmission. When the clutch pedal is pressed, the noise disappears. When the car is in neutral or driving through the gears, it’s evident and sounds like synchronized noise as the revs increase.

My first thought it would be the throw out bearing in the clutch, got the clutch replaced and after the job, the noise was still there.

So this leaves me guessing it is something internal within the gearbox. Perhaps the internal shaft bearing, please correct me if I’m wrong.

Is there a risk of damaging the transmission if I’m driving the car with the input shaft bearing rattling?

Are there any temporary fixes the help reduce the rattle, perhaps a thicker transmission oil?

Does the gearbox need to be disassembled to replace the input shaft bearing?

Any help will be appreciated.

Thanks!!!

[LeiseyJr]

With doglegs it is much more likely it is a worn front layshaft/countershaft bearing. Thicker oil could help it, you don't lose anything trying it.

When the layshaft bearing goes it takes everything else out with it, it is nasty. I would replace the input and layshaft bearing.

Some transmissions can make noise for years depending on how they are driven. I ignored mine for a year and drove it hard and it did let go on me. The magnetic drain plug and the noise gave me plenty of warning. That is about the only way to monitor it.


My preferred fluid for the dogleg is Redline MT90, but more recently I only use:
https://www.amazon.com/dp/B004LF1U1S?ps ... ct_details

[Preyupy]

Have you had the oil changed recently? What did the drain plug look like? What oil did they put back in? A lot of modern manual transmissions are designed with thin oils in mind to help with fuel mileage (not necessarily for long gearbox life). The BMW 265 and 245 series gearboxes do have a tendency to "rattle" at idle when they are warm in neutral. Light weight flywheels make it worse (this is why most modern cars come with dual mass flywheels to help eliminate gearbox noise). Does your gearbox "whine" when in the lower gears under light to heavy loads? If it does make noise under load I agree it is likely you have a front counter shaft bearing that is starting to go. If it is just the "rattle" at idle in neutral try the Redline MT90 or the Motool and see if it makes any difference.

If the drain plug is "FUZZY" when you pull it out you need to get inside the gearbox and find out what is going wrong ASAP. There are no replacement gears or shafts and 265/5 gearboxes are getting rare and expensive.

[LeiseyJr]

viewtopic.php?p=1434787#p1434787

What could happen if you ignore the noise

[Balame]

Thanks for the in response.

Gearbox was replaced just over a year ago from a 265/6 box.

Bit hard to determine if it a whining soud or rattlle under heavy loads in lower gears, its more of a synchronised rattling/whine sound that becomes louder as the RPM's increase.

Can you please share the part numbers of the input shaft bearings and the bearing beneath the ISB for the 265/5 box?

I wont be doing any works to the synchro's or any further internal work to the box as the gears are fine and don't want to mess with them. Have heard multiple horror stories from forums here in the AU regarding issues after replacing synchros.

Is there anything else that should be replaced whilst replacing the ISB? If so, can you please share the part numbers, that will be greatly appreciated.

Looking forward to having this issue sorted to enjoy the car once again...

With doglegs it is much more likely it is a worn front layshaft/countershaft bearing. Thicker oil could help it, you don't lose anything trying it.

When the layshaft bearing goes it takes everything else out with it, it is nasty. I would replace the input and layshaft bearing.

Some transmissions can make noise for years depending on how they are driven. I ignored mine for a year and drove it hard and it did let go on me. The magnetic drain plug and the noise gave me plenty of warning. That is about the only way to monitor it.


My preferred fluid for the dogleg is Redline MT90, but more recently I only use:
https://www.amazon.com/dp/B004LF1U1S?ps ... ct_details

[Balame]

Thanks for the in response.

Gearbox was replaced just over a year ago from a 265/6 box.

Bit hard to determine if it a whining soud or rattlle under heavy loads in lower gears, its more of a synchronised rattling/whine sound that becomes louder as the RPM increase.

Can you please share the part numbers of the input shaft bearings and the bearing beneath the ISB for the 265/5 box?

I wont be doing any works to the synchro's or any further internal work to the box as the gears are fine and don't want to mess with them. Have heard multiple horror stories from forums here in the AU regarding issues after replacing synchros.

Is there anything else that should be replaced whilst replacing the ISB? If so, can you please share the part numbers, that will be greatly appreciated.

Looking forward to having this issue sorted to enjoy the car once again...

Have you had the oil changed recently? What did the drain plug look like? What oil did they put back in? A lot of modern manual transmissions are designed with thin oils in mind to help with fuel mileage (not necessarily for long gearbox life). The BMW 265 and 245 series gearboxes do have a tendency to "rattle" at idle when they are warm in neutral. Light weight flywheels make it worse (this is why most modern cars come with dual mass flywheels to help eliminate gearbox noise). Does your gearbox "whine" when in the lower gears under light to heavy loads? If it does make noise under load I agree it is likely you have a front counter shaft bearing that is starting to go. If it is just the "rattle" at idle in neutral try the Redline MT90 or the Motool and see if it makes any difference.

If the drain plug is "FUZZY" when you pull it out you need to get inside the gearbox and find out what is going wrong ASAP. There are no replacement gears or shafts and 265/5 gearboxes are getting rare and expensive.

[Preyupy]

The input shaft bearing is 23 12 1 204 580
front countershaft bearing is 07 11 9 981 432
you will need the front gasket 23 12 1 222 357
at least 1 case gasket 23 12 1 222 359
input shaft seal 23 11 1 228 314