Transmission whine at low speed?

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Ethanh100
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Joined: Mon Apr 27, 2020 3:56 pm
Location: New Canaan, CT

Transmission whine at low speed?

Post by Ethanh100 »

Ive recently started to notice a whining coming from what sounds like the 5 speed transmission on my '87 M6 but I'm not too sure, so I was looking for some help to diagnose it.

I only notice it when im moving at low speeds (5-20mph) and it sounds like its coming from behind/under the middle of the dashboard (the trans tunnel). It doesn't sound like its coming from one of the corners up front like a wheel bearing. The whine isn't loud but its noticeable, and maybe has gradually been getting louder over the course of 50 miles. It happens when the car is in gear or in neutral rolling, so it would be something on the output side of the trans, or maybe a driveshaft bearing? my thought was low fluid in the transmission, that hasn't been checked in a number of years, but thats just my guess. The transmission is also hard to shift sometimes (like when sitting at a stop and shifting to 1st, but it has always been like that so I wasn't sure if thats unusual).

If anyone thinks it is the transmission, should I just open the fill port and pump some more fluid into there and see if it takes any? Or should I change the fluid entirely (are there any filters ect. that need to be changed as well)? Thanks
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sideshowbob
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Location: Hampshire UK

Re: Transmission whine at low speed?

Post by sideshowbob »

Hi, does the noise increase or decrease when you depress the clutch...if it does it could be the thrust bearing.
Ethanh100
Posts: 23
Joined: Mon Apr 27, 2020 3:56 pm
Location: New Canaan, CT

Re: Transmission whine at low speed?

Post by Ethanh100 »

sideshowbob wrote: Sun Aug 15, 2021 5:11 pm Hi, does the noise increase or decrease when you depress the clutch...if it does it could be the thrust bearing.
Forgot to mention, no change when pressing the clutch in.
wfwright2 wrote: Sun Aug 15, 2021 5:29 pm I am not a transmission expert, but my 2 cents.

If there is no history of changed fluid, or if it has been a while, just drain and refill the transmission. US models called for Dexron ATF, thinking since is too use Red Line MTF or MTF-90 or a 50/50 blend of ATF and either MTF. Others will have their own ideas of best fluid choice.
Original BMW maintenance schedule is to replce fluid every 15000 miles.

There is no filter, s just get transmission warm, drain and refill.
There have been discussions that the location of the filler fitting is a bit low to allow enough fluid, but if used and changed often enough, should be adequate.

I have heard of input bearing and first internal input shaft roller bearing failure due to improper/inadequate lubrication.

Metric Mechanic has a discussion of weakness in the G680 transmission.
Thanks for the input. Sounds easy enough that I should just change the fluid and see if theres any change. Its probably due by now anyway.
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Ralph in Socal
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Re: Transmission whine at low speed?

Post by Ralph in Socal »

Word of caution. Make sure you can open the fill port before draining!!

If you fill cold, operating level will be a little higher due to thermal expansion. Not really critical though and you really can’t fill at operating temp anyway

Ralph
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Ethanh100
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Joined: Mon Apr 27, 2020 3:56 pm
Location: New Canaan, CT

Re: Transmission whine at low speed?

Post by Ethanh100 »

Ralph in Socal wrote: Mon Aug 16, 2021 7:12 pm Word of caution. Make sure you can open the fill port before draining!!

If you fill cold, operating level will be a little higher due to thermal expansion. Not really critical though and you really can’t fill at operating temp anyway

Ralph
Yep Will be sure to crack that loose before opening the drain plug. Thanks for the input.
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