Transmission Squeak on Acceleration After Shifting *Video Update*

[MJ6]

I've started getting a light "squeaking" sound that appears to be emanating from the shifter area (6spd), but only under increased acceleration (above 4k RPM) while shifting from 1st to 2nd, and 2nd to 3rd. If I'm just driving around and shifting normally, there's no issue.

Driveline modifications are Auto Solutions SSK w/70a bushings and bronze inserts, Rogue Transmission Mounts, CDV Delete, Ultimate Clutch Pedal and ClutchMasters FX250 clutch (stock DM Flywheel).

It's not so much a squeal, but an elongated and deeper sounding squeak that lasts for about a half second when releasing the clutch pedal in second gear and applying the throttle. My first guess was clutch slippage, but I can drop the clutch in 1st from 4k with no slipping and no "squeak".

I'm wondering if it could be bushing related, either in the bushings themselves are binding or perhaps the transmission mounts aren't up to the task. I plan on reapplying some lithium grease to the shifter bushings to see if might be the cause, but if someone has experienced something similar or has any suggestions I'm all ears.

[MJ6]

On the off chance that someone else experiences this same issue, I'm going to document my findings and steps taken towards a solution; I'm also going to try and get a decent video depicting the noise if I can as well.

Checked the transmission mounts to see if they were loose or failing; they weren't broken or really "loose", but I retighten them anyways. I also sprayed down the the shifter linkage with white lithium grease to mitigate any potential binding.

The next step will be to change the transmission fluid.

[MJ6]

No change after checking the transmission mounts and greasing up the shifter linkage, so next up will be transmission fluid.

I did notice that it only presents itself after the car has warmed up however.
Also, I was able to capture the sound on video: once from the drivers seat and once from the front console.

If anyone has any ideas, please chime in as I'd prefer to avoid the stealership.

[mapster37]

i doubt changing the fluid will eliminate that noise. does the noise only happen on a particular shift ie: 1-2 or any shift?

[MJ6]

Originally Posted by mapster37

i doubt changing the fluid will eliminate that noise. does the noise only happen on a particular shift ie: 1-2 or any shift?

Currently only 1st to 2nd and 2nd to 3rd, and only after the transmission has been brought up to operating temp.

Of note, there is no burning clutch smell and I don't experience any power loss or clutch slippage.

[mapster37]

sounds like there is something rubbing/touching. can the noise be felt in the shifter?

[MJ6]

Originally Posted by mapster37

sounds like there is something rubbing/touching. can the noise be felt in the shifter?

It does sound like something rubbing, which is why my first inclination was the shifter linkage or a loose mount. Feel wise, it's difficult to tell; there's no real discernible change in feedback when the noise presents itself, but as the tolerances are tighter there's always a little vibration through the shifter regardless.

Another possibility could l be the throw out bearing rubbing on the shift arm or output shaft on engagement, but to me that wouldn't explain why it's only present under shift load and only between the first three gears (unless it's torque dependent in some way). It's honestly driving me nuts trying to figure this one out as I can't find anyone that's had a similar issue.

[TopJimmy]

Bro, I hesitate to say it might be the sound of a synchro buzzing as it's trying to sync a gear. I had a similar buzz trying to shift 1-2 at the drags after the trans oil got hot.

I switched out the MT6 oil to Motul DCTF-HT and it stopped. Not sure if this is your fix but it didn't cost much.

[MJ6]

Originally Posted by TopJimmy

Bro, I hesitate to say it might be the sound of a synchro buzzing as it's trying to sync a gear. I had a similar buzz trying to shift 1-2 at the drags after the trans oil got hot.

I switched out the MT6 oil to Motul DCTF-HT and it stopped. Not sure if this is your fix but it didn't cost much.

Honestly, that would be best case scenario at this point. I changed the transmission fluid about a year and a half and 13k ago with the standard 75W90 BMW fluid, but since that time I've also had three extended sessions of back to back dyno runs which I'm sure heat up the fluid in there pretty substantially. In the back of my mind I'm hoping it just wore out the transmission fluid and it needs a flush.

I do have Motul DCTF on the way (couldn't find HT), but I'll be flushing it on Saturday and will report back with the results.

[Phatazz7]

are you able to replicate the noise with the car in idle by pushing the clutch pedal in and out or is it only when shifting?

[MJ6]

Originally Posted by Phatazz7

are you able to replicate the noise with the car in idle by pushing the clutch pedal in and out or is it only when shifting?

Negative, so I know it's not a worn throwout bearing, only right after the shift.

I'm changing the transmission fluid tomorrow though with Motul DCT-HT so I'll report back with what I find out.

[MJ6]

Well, I changed the transmission fluid and unfortunately it doesn't seem to have affected the issue: the squeak is still present.

I hesitate to take it in to have it looked at though, not only because chasing down a "squeak" is generally and effort in futility, but also because it's not effecting performance. That and I've already had this transmission torn apart twice already finding a clutch that works, and really loath the idea of having to pay for that again.

This car really is a love hate relationship.

[MJ6]

More digging.

I found a post over on an M5 forum which sounds like it's very similar to what I'm currently experiencing: no clutch slippage, still shifts crisply, only happens after the shift coming off the clutch pedal.

https://www.m5board.com/threads/stra...sively.250586/

"Yes, it could be the throwout bearing. When you let up the clutch pedal, the bearing goes from loaded and spinning at the clutch speed to suddenly unloaded but still spinning fast. That can allow the balls in the bearing to lock up and skid instead of roll if the grease has dried out. Skidding causes a high pitched screech."

I'll be taking it into my mechanic who performed the clutch install hopefully next week, and will report back with what we find.

[MJ6]

So my mechanic and I have it narrowed down to either the clutch/flywheel interface slipping, or the pilot bearing starting to crap out.

But here's my conundrum:
- If it's the clutch slipping, it means at the very least a new, higher rated clutch.
- If it's the pilot bearing, I'll need an entirely new flywheel as the bearings are apparently integrated and not sold separately.

So what did I decide to do? I bit the bullet and purchase a tried and tested setup: the Spec Twin Disk SB55PT P-Trim. I also have some time off coming over the next few weeks, so I might attempt to install it myself as I've already paid to have two clutches installed already.

That being said, anyone have access to a decent DIY on this platform?

[Vertix]

Did this fix your issue?

Also I'd really love to hear your thoughts in the clutches youve tried. Youve tried the 2 im looking at currently (fx250 with stock DM flywheel or the SB55PT P-Trim).

Which one have you prefered the most from simply a street driving point of view?

How does each compare to stock?

[MJ6]

Originally Posted by Vertix

Did this fix your issue?

Also I'd really love to hear your thoughts in the clutches youve tried. Youve tried the 2 im looking at currently (fx250 with stock DM flywheel or the SB55PT P-Trim).

Which one have you prefered the most from simply a street driving point of view?

How does each compare to stock?

Comparison wise between the two, the FX250 with DM flywheel had the best street manners, likely due to keeping the OEM flywheel. One thing I did notice was that the catch point was really high on the pedal, like within the first 2-3 inches of travel it would disengage the clutch. Truth be told I kind of liked it for quick shifting, but it took some getting used to. The sound I was hearing between low gear shifts I believe was a result of re-using the flywheel instead of mating the clutch to a new one or attempting to have it resurfaced; my theory after looking at the clutch and flywheel mating surface was that it wasn't making full contact. I'm pretty sure it would have been able to hold the power I was making easily enough (707WHP/687WTQ) but I was constantly questioning if it could hold up in longevity as ClutchMasters doesn't really specify what it's rated for.

The Spec SB55PT P-Trim is a different beast, but so far I like it. Street manners are excellent for a twin disk and single mass, which I attribute to a heavier flywheel and the carbon-graphite disks. The clutch pedal is a bit firmer due to the plates ability to hold more power, but it's nothing extreme. The catch point for the clutch pedal is more close to stock as well (closer to the end stroke) which makes modulation easier. The one aspect I'm waiting to see if it improves though is lower gears entering the shift gate. 1st - 2nd and 2nd - 3rd can be a bit harder to get into, again though this may be due to the heavier duty pressure plates. Mind you, it's still in the break-in stage right now so that may change as it gets some more miles under its belt.

As a caveat though, I'm also running an Ultimate Clutch Pedal with the helper springs removed, CDV delete, and AutoSolutions SSK with upgraded shifter bushings, so your mileage may very depending on your supporting mods.

[Vertix]

Really appreciate that man! I think youve helped me puleld the trigger on the FX250 + stock DM flywheel. Thanks for the solid info!