Transmission Compression Springs

[dukeofchen]

For months now I've been chasing down an issue with my 6MT – it gets stuck in gear or won't enter the next gear when the revs are above ~3-4k, and is particularly bad when dealing with gears 1 / 3 / 5. Pedal feel is fine, doesn't pop out of gear, no weird noises, clutch fully engages / disengages just fine. Changed fluids, mounts, refreshed shifting mechanism, etc.

Based on some searches it seems like SMGs have an issue with compression spring #9, where it will refuse to shift at higher RPMs, or will wait until the RPMs drop. I've basically been forced to drive my car in that fashion as well so I'm wondering if the same issue could be presenting itself in a 6MT.

I'd give replacing #9 a go, but the diagram seems to be different than the pictures of SMGs I've seen of a press fit plug with the spring behind it.

How does one actually access this spring on a 6MT? Also could #15 / #17 have anything to do with this issue? My understanding is that #2 / #6 are replaced for centering slop which isn't an issue for me.

Thanks guys, my baby hasn't seen 5k RPM in months and it's an absolute travesty.

[Lukem3]

Start with basics, these transmission being getrag dont have much internal issues if taken care of. Besides the occasional synchro failure or leaking seals.

You took care of tranny mounts, what about motor mounts. This can cause the no shift issue although it would be more speed related rather than rpm.

It seems like clutch is still partially dragging, not allowing u to change gears at higher rpm. Try rebleeding the slave cylinder, if that doesn't help swap in a brand new slave. Make sure you're bleeding it properly. That most likely will take care of the issue. If it doesn't you have a burnt clutch or pressure plate. These clutches are self adjusting, so even if it feels fine it could be worn out or burnt up. If the slave cylinder was the culprit and you drove like that for a long period of time, there is a possibility it started damaging or prematurely wearing the clutch aswell since it wasn't applying adequate pressure to fully disengage before gear changes.

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[Gt4]

You need to change the #9 spring, it will be broken for sure. I opened 3 transmissions lately, 2 SMG and 1 6mt and all 3 had broken springs. Even on a 53k miles transmission...

That spring is located behind the #11 sensor. You will need a 22mm wrench to remove the sensor.

This diagram seems wrong btw. #9 is in the same hole as #11

[sapote]

It seems like clutch is still partially dragging, not allowing u to change gears at higher rpm.

This can be checked easy on a slope driveway or road: engage 1st or R then press down clutch pedal slowly until car starts rolling, then notice how much more the pedal can go down before hitting stopper. It should have enough free travel.
But I wonder why he has more issue with the odd gears (1,3,5) which are engaged with the shift rod moving rearward (shift knob moves forward)

[Lukem3]

Any update?

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[sapote]

it gets stuck in gear or won't enter the next gear when the revs are above ~3-4k, and is particularly bad when dealing with gears 1 / 3 / 5.

When it's hard to shift into 1/3/5 then it means the main shift rod jammed by a broken pin with roller #8, or something jammed the pin from moving in/out such as broken spring #9 bind inside the bushing. All other springs are for detent on the internal shift rod, and if your car is an older model, then it's better to swap out the 3 balls under the springs #17 with the updated sleeves, but don't touch the two fat pins in between those 3 springs/balls.
But I don't see why moving the shift rods easy or hard have anything to do with high rpm. The only thing makes sense is the synchro has more resistance at high rpm with mismatched dogteeth and cause more load on the shift rod in addition to the damaged parts above.
I wonder why BMW didn't update the ball #14 for 5th shift rod detent to the sleeve as #17 repair kit.

[dukeofchen]

Start with basics, these transmission being getrag dont have much internal issues if taken care of. Besides the occasional synchro failure or leaking seals.

You took care of tranny mounts, what about motor mounts. This can cause the no shift issue although it would be more speed related rather than rpm.

It seems like clutch is still partially dragging, not allowing u to change gears at higher rpm. Try rebleeding the slave cylinder, if that doesn't help swap in a brand new slave. Make sure you're bleeding it properly. That most likely will take care of the issue. If it doesn't you have a burnt clutch or pressure plate. These clutches are self adjusting, so even if it feels fine it could be worn out or burnt up. If the slave cylinder was the culprit and you drove like that for a long period of time, there is a possibility it started damaging or prematurely wearing the clutch aswell since it wasn't applying adequate pressure to fully disengage before gear changes.

The motor mounts have less than 20k on them so all should be fine there. I'll be doing a full fluid flush just to be sure, hopefully in the next few days if I can find the time. While I agree that hydraulics are an obvious culprit, I haven't experienced any errant clutch engagement outside of these situations, and even in the lockout situations if I fully clutch in the RPMs will drop normally but I'll still have trouble getting it out of gear. It feels more as if there is something physically impeding the gear lever, which is what led me to these compression springs.

You need to change the #9 spring, it will be broken for sure. I opened 3 transmissions lately, 2 SMG and 1 6mt and all 3 had broken springs. Even on a 53k miles transmission...

That spring is located behind the #11 sensor. You will need a 22mm wrench to remove the sensor.

This diagram seems wrong btw. #9 is in the same hole as #11

Awesome, this is really good to know, especially the fact that the realoem diagram is wrong. I went ahead and ordered the spring since it was only ten bucks, so hopefully it isn't too much of a pain to swap out.

When it's hard to shift into 1/3/5 then it means the main shift rod jammed by a broken pin with roller #8, or something jammed the pin from moving in/out such as broken spring #9 bind inside the bushing. All other springs are for detent on the internal shift rod, and if your car is an older model, then it's better to swap out the 3 balls under the springs #17 with the updated sleeves, but don't touch the two fat pins in between those 3 springs/balls.
But I don't see why moving the shift rods easy or hard have anything to do with high rpm. The only thing makes sense is the synchro has more resistance at high rpm with mismatched dogteeth and cause more load on the shift rod in addition to the damaged parts above.
I wonder why BMW didn't update the ball #14 for 5th shift rod detent to the sleeve as #17 repair kit.

I definitely don't know enough to explain the correlation with high RPMs, but based on everything I've read over on the uk forum SMGs with a broken #9 spring also only exhibit the difficulty shifting at higher RPMs. All speculation until the spring arrives on Monday and I swap it out, but I'm really hoping that's all this is. Will report back with my findings when complete.

[Casa de Mesa]

Dredging up an older thread while chasing down very similar shifting issues as dukeofchen per his thread here.

When it's hard to shift into 1/3/5 then it means the main shift rod jammed by a broken pin with roller #8, or something jammed the pin from moving in/out such as broken spring #9 bind inside the bushing.

^^THIS is what I'm experiencing and it's been getting progressively worse recently. On higher RPM 2nd>3rd shifts, as well as 4th>5th, I've had a hard time finding 3rd/5th. Then when trying to pull it out of 5th (in particular), it resists getting out of gear more than it should.

All other springs are for detent on the internal shift rod, and if your car is an older model, then it's better to swap out the 3 balls under the springs #17 with the updated sleeves, but don't touch the two fat pins in between those 3 springs/balls.

I'm sure it will be obvious once I start pulling stuff apart, but where is #17 (and the collective parts) located? It doesn't show it too well on the RealOEM diagram.

I wonder why BMW didn't update the ball #14 for 5th shift rod detent to the sleeve as #17 repair kit.

By any chance, can you explain this a little more? This feels like it's something I might need to check, R&R if required.

I'm crawling under the car today to check for anything obvious:

• Shifter issues - mine is STOCK with the exception of UUC Double Sheer Selector Rod/DSSR and was completely refreshed 20k miles ago (this may finally push me towards an AutoSolutions, Rogue or UUC SSK if anyone has suggestions here).
• Slave cylinder recently bled (about 1k miles and 6mo ago) - will check for leaks
• New BMW MTF-LT-2 fluid - car has 75k miles and has had fluid changed 5 times. I dropped the Redline fluid out of it thinking that could be the culprit. Nope.
• Loose transmission mounts - will check
• Engine mounts recently done - doubt this is it but will look
• Etc.

Thanks to the OP for both of these threads and all the replies, it has given me a path forward to check.

Edit: first time using these stands. LOVE THEM. For this type of job, only thing better is a lift.

[sapote]

Casa,
I believe OP has SMG and yours is manual?

viewed from rear:
#17: these parts are at upper right , rear.
#14: upper left, middle, near reverse and GPS switches.
There are 4 internal shift rods:
R, 1/2, 3/4 are at #17
5/6 is at #14 with ball and sprint detent.

[Casa de Mesa]

Hi thanks for the reply sapote literally just about to crawl under the car. This info will be gold, thank you.

Yes, mine is manual and I think the OP has 6MT as well.

[dukeofchen]

Should have closed out this thread with the final verdict on my car. The transmission spring was originally a hunch having read about SMGs snapping the spring, where the SMG exhibits a behavior similar to how I was shifting to drive around the problem (SMGs with a broken spring would significantly delay upshifts until RPMs dropped, or skip gears). In the end my spring was fine so it was not the problem, and I never found a verdict on whether this is something that happens on 6MTs with any regularity despite sharing the same Getrag box.

After continuing with the clutch / flywheel job per the other thread, I discovered that it was not only the plastic pivot pin that had completely sheared, but my throwout bearing also had a really nasty crack in it. Not sure which failure led to which, but considering the clutch I pulled out at 180k miles appeared to be the factory one, it was long overdue. The combination of broken pivot pin and TOB meant the clutch fork was out of alignment and unevenly disengaging the clutch, creating this condition at high RPMs. It's really a wonder that something like this wasn't causing any observable noises by my ear, but I suppose with the clutch in everything is under pressure / compressed and therefore wouldn't rattle. I was having the most issue getting in / out of gears 1/3/5 similar to what you describe, but as time wore on just about any attempt to shift above 3k would have the shifter fighting me or grinding if I really pushed the issue.

It seems like you're going down the same diagnostic checklist that I did before resorting to pulling the tranny. I'd say make sure all those smaller items check out, but if you don't find anything signs are probably pointing towards dropping the transmission.

[Casa de Mesa]

It seems like you're going down the same diagnostic checklist that I did before resorting to pulling the tranny. I'd say make sure all those smaller items check out, but if you don't find anything signs are probably pointing towards dropping the transmission.

Yep, I certainly am!

I fear I'm likely going to need to drop this tranny. I saw the broke pivot in your other post, didn't know about the TOB. My car has *only* 75k miles so I'm hoping I don't have similar issues to you, but man, the symptoms certainly sound the same so I'm not holding out hope...

[dukeofchen]

Yep, I certainly am!

I fear I'm likely going to need to drop this tranny. I saw the broke pivot in your other post, didn't know about the TOB. My car has *only* 75k miles so I'm hoping I don't have similar issues to you, but man, the symptoms certainly sound the same so I'm not holding out hope...

Best of luck - don’t know your level of experience but if it’s your first time doing the job (as it was mine) would be happy to share some of my notes / resources I used to make it a smoother process.


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[Casa de Mesa]

Unfortunately, nothing obvious is loose or leaking. So it points to other issues I can't visually inspect. Either the springs and detents pictured above, or broken pivot, TOB, or other.

You need to change the #9 spring, it will be broken for sure. I opened 3 transmissions lately, 2 SMG and 1 6mt and all 3 had broken springs. Even on a 53k miles transmission...

That spring is located behind the #11 sensor. You will need a 22mm wrench to remove the sensor.

This diagram seems wrong btw. #9 is in the same hole as #11

Is it possible to remove these driver side springs/detents with the tranny in place? I can get to #14-16 pretty easily but #8-11 look pretty tight. I need to head back to my other shop to pick up tools (22mm wrench), but it looks like #8-11 might have clearance issues against the transmission tunnel once it's loosened.

Also, is there anything to worry about once these are out? As in, would pulling these out to inspect cause something else to go haywire? It looks like "no" but have to ask...

Lastly, #17 appears like the tranny has to come out to get to...



dukeofchen thank you kindly. I have had transmissions out of lots of other cars, but fortunately have never needed it out of this car. I may take you up on that but so far everything seems fairly straightforward, except for my questions just above 😂

[Casa de Mesa]

Answered my own question. Got #8-11 out, super easy to do. It was barely tight for a 22mm and then easily hand spun out. Going in to get the spring a detent next.