Transmission grinding second gear (Solved)

[thehalcyon]

Ya thanks, are you talking about the sychromesh fluid? I was told about trying this as a last resort, but like you said to expect it to be the synchros and needing a new transmission. I had redline D4 ATF put in a few months ago, so it's not that. Indeed out of warranty, a local guy in my bmw club has a used transmission for sale $1000 that is probably negotiable too, so may be able to get it for around 800 (CAD) or so.

[Gray_Panther]

Good thing you were on warranty!

[Matticus91]

Originally Posted by thehalcyon

Ya thanks, are you talking about the sychromesh fluid? I was told about trying this as a last resort, but like you said to expect it to be the synchros and needing a new transmission. I had redline D4 ATF put in a few months ago, so it's not that. Indeed out of warranty, a local guy in my bmw club has a used transmission for sale $1000 that is probably negotiable too, so may be able to get it for around 800 (CAD) or so.

If you can get a trans for that much then jump on it, they usually are much more than that. Just make sure you have the right trans code because there are a few subtle differences between them.

[thehalcyon]

Originally Posted by Gray_Panther

Good thing you were on warranty!

Sorry if it was not clear, I'm not under warranty. I would have to pay this out of pocket, im trying the engine and trans mounts first since I think they've gone soft anyway, we'll see if it helps but its practically grinding every time into 2nd now... so if that doesnt cure it then used transmission it will be.


Matticus91: thanks for the tip on the transmission code, i will double check that its compatible. (its from a 2008/9 335i)

[Dackelone]

Originally Posted by Get Inline

synchros almost always wear out prematurely from constant high RPM shifting.

No. The syncros wear out from down shifting from high rpms in THAT gear. Say from going from 5th/6th to 3rd or 2nd gears. Then you start to notice it on up shifts when that syncro can no longer do its job.


thehalcyon sometimes I've seen special gear oils that can hide a bad syncro. BG Products... BG Syncro-Shift is a good product. But it doesn't work on all cars. But its worth a shot. Normally you can only buy it from a repair shop... BG doesn't usually sell to the public. A one liter bottle runs around $25. You will need two liters for the manual trans.

I don't think its your motor or trans mounts. Take out your CDV... and bleed the clutch system. But IF your getting grinding... the damage is done and you will need a new trans or used trans.

Dackel

[MightyMouseTech]

Originally Posted by Get Inline

I know two friends who are constantly redlining second gear (banging it into third)

and their third gear synchros are fucked.

When we have poor syncros on Hondas, they tell us to put in GM Friction Modified Syncromesh fluid. Makes the syncros much happier.

We have also had many bulletins that skip shifting is a large part of what wears them out. So always go in order 1-2-3-4-5 etc, don't go from 2nd to 4th or 3rd to 5th or 6th etc. They tell us to deny warranty repairs for drivers that skip gears.

[MightyMouseTech]

Originally Posted by Get Inline

even in the higher gears, when you shift smoothly and the difference between the gears is not huge?

Always.

[Dackelone]

Originally Posted by Get Inline

I know two friends who are constantly redlining second gear (banging it into third)

and their third gear synchros are fucked.

Nothing lasts forever. If you beat on it... it will break/wear out.

Dackel

[Lucky1]

Originally Posted by Dackelone

Nothing lasts forever. If you beat on it... it will break/wear out.

Dackel

Okay but if you engage the gear smoothly even at high rpms by giving the right amount of throttle and slipping the clutch does it not prevent premature synchro or other kinds of wear? I never "bang" a gear in by just dumping the clutch all the way. Even on the track I always smooth the shift out by slipping at the friction point til I can release it smoothly. No idea why anyone would do otherwise except maybe they're brainwashed to believe that a little slipping of the clutch is more disastrous than slamming your transmission into gear when engine speed doesn't match shaft rotational speed. Yet I have been passenger while the drive is constantly lurching the car in ever gear without smoothing the shifts out.

[Dackelone]

Originally Posted by Lucky1

Okay but if you engage the gear smoothly even at high rpms by giving the right amount of throttle and slipping the clutch does it not prevent premature synchro or other kinds of wear? I never "bang" a gear in by just dumping the clutch all the way. Even on the track I always smooth the shift out by slipping at the friction point til I can release it smoothly. No idea why anyone would do otherwise except maybe they're brainwashed to believe that a little slipping of the clutch is more disastrous than slamming your transmission into gear when engine speed doesn't match shaft rotational speed. Yet I have been passenger, while the driver is constantly lurching the car in ever gear without smoothing the shifts out.

Wear on the synchro can be caused by a lot of things. But mostly from fast "speed shifting" shifts or downshifts from a high gear into a low(er) gear... like when going from 5th/6th to 2nd/3rd - quickly. Or not using the clutch.

The synchros are made from a soft metal like brass... and they do wear over time.

Worn synchros can also be caused by resting your hand on the shift lever(while driving) or fast shifts or quick shifts when the trans fluid is still cold and causing some wear on the synchro rings. Or not fully depressing the clutch(ei clutch pedal stop) or the CDV not allowing fast movement of the clutch slave in the 1st/2nd gears. There is a lot of things that can cause wear.

Also... driving style... here in Europe... no one drives fast/hard in 1st or 2nd gears. Heck... I really don't go full throttle unless I am in 4th/5th/6th gears. And most of the time I just floor it in 6th!(when I am on the Autobahn)

Driving in the US is different... and it does wear out the equipment if you drive like a nut. Jack rabbit starts are the norm and people tend to drive hard in the lower gears. More 0-60 mph runs or traffic light racing.

In Germany it's more about driving from 85 mph to 185 mph!
Traffic light racing is not allowed over here. It's a big no no.

I shift fast, sometimes... but I never abuse my trans. It sounds like the way you are shifting in a totally fine manner too.


One other thing we haven't really talked about... is servicing the trans. Even though BMW says the trans fluid is "lifetime" fluid... I don't believe in that. I've changed my trans fluid four times in 90K miles. To me some trans oil is a whole lot cheaper than a new transmission.

IF you track your car... changing ALL your fluids is needed IF you intend on keeping the car long term.

Dackel

[1and1]

If it's not too far off topic for this thread, what's the reason for being gun shy on rebuilding/servicing the 6MT?

I would expect things like synchros and shift forks to be basic wear items needing service/replacement, not a reason to scrap the whole box? Often things like the OE shift forks come with nylon or plastic pads and upgrading to brass is a huge improvement.

[Matticus91]

Originally Posted by 1and1

If it's not too far off topic for this thread, what's the reason for being gun shy on rebuilding/servicing the 6MT?

I would expect things like synchros and shift forks to be basic wear items needing service/replacement, not a reason to scrap the whole box? Often things like the OE shift forks come with nylon or plastic pads and upgrading to brass is a huge improvement.

You can't buy the parts, BMW only makes it available as a whole unit

[Dackelone]

Originally Posted by 1and1

If it's not too far off topic for this thread, what's the reason for being gun shy on rebuilding/servicing the 6MT?

I would expect things like synchros and shift forks to be basic wear items needing service/replacement, not a reason to scrap the whole box? Often things like the OE shift forks come with nylon or plastic pads and upgrading to brass is a huge improvement.

Manufacturers have figured out that its just cheaper to throw in a new or rebuilt transmission than to pay a "tech" once or two or three times to repair a trans for a customer under warranty. Many techs are just parts replacers and can't trouble shoot a repair. IF there is no code there is no problem.

And when it comes to transmissions... it can be very expensive... for the Manufacturer to pay for the repairs until the car goes out of the warranty period. So... most manufacturers just throw in a rebuilt trans and call it a day.

BMW does this too. But unlike just about every other manufacturer... BMW does NOT sell individual transmission parts - thru their parts dept. It's all or nothing with BMW.


Btw... on a side note... I use to work at a fairly larger VW/Subaru dealership... the top techs were making $100K plus. 18 service bays, etc... anyways... we had this one guy... he was the "unit man" for Subbie. Unit man means he did all the trans and engine jobs. So when a car came in with a trans problem... he would get the car. But he had no idea how to rebuild a Subbie A/T trans... so he would out the car on his lift... drain all the trans fluid out... then take the car into the back lot... rev the engine in gear until the trans failed. Then tow the car back onto his bay and replace that ($8K!)AT trans. Subaru of America couldn't figure out why our transmission replacement rates were so high! Our parts & service managers always won the quarterly sales contests and everyone was happy. lol

This is why you don't want just anyone to overhaul your trans. Not many techs can do it. And these days I bet its very few guys who know how to do it correctly without you having to pay him to "learn" on your car!

Dackel

[1and1]

Yeah, on average I wouldn't expect, or want, a dealership to rebuild a trans, but I have a low regard for the average dealership shop monkey. I do totally respect there are a few true quality wrenches working in dealership shops, but feel they're getting few & far between.

I'd expect a good trans shop to be able to do the work however, and am perfectly willing to rip one apart myself even. Alas a quick pass through google looks like BMW has gone out of their way to make it not end user friendly. Unobtanium special tools etc., I read lots about BMW rebuilding them, but not many others.

Just spoiled I guess, coming from the Mazdaspeed world where they'll happily sell you parts for anything- bearing, synchros, single gears to full shaft-mounted gear sets ready to drop in. One of our semi-popular upgrades was changing out the gas trans gears for diesel gear sets for the longer 1st & 2nd gears. Shift fork swaps was an afternoon project.

Yeah, I know, welcome to the new world Eric.... I'm not in Kansas anymore

[Stubbie Blue]

What about wear on the 1st gear synchros? I usually avoid shifting into 1st if the car is moving due to the high rpm gap that the synchros have to spin 1st gear up to. You can feel it in the amount of force required to get the stick into 1st. So if I really need to get into 1st I'll double clutch it and it goes right in, even up to 30mph. What do you guys do?

[Dackelone]

Originally Posted by Stubbie Blue

What about wear on the 1st gear synchros? I usually avoid shifting into 1st if the car is moving due to the high rpm gap that the synchros have to spin 1st gear up to. You can feel it in the amount of force required to get the stick into 1st. So if I really need to get into 1st I'll double clutch it and it goes right in, even up to 30mph. What do you guys do?

Yeah... anytime the shift lever doesn't want to move... its not good for the trans. I would do the same as you... double clutch it.

But normally I would avoid doing that all the time. Every once in awhile is ok. But perhaps you can get by just using second gear.

It's the same when I am at a traffic light... I never shift first into first gear. I always move the shifter into 2nd, and then first gear. When you move the shifter into 2nd gear... the trans internals stop spinning - or so I believe. It just feels better to me and my trans. I also go into 2nd before shifting the car into reverse as well. Even though reverse gear is synchronized on BMW's.. it's just a habit I have from my VW days with a non synchronized reverse gear.

Dackel

[minirips2]

Originally Posted by Dackelone

Yeah... anytime the shift lever doesn't want to move... its not good for the trans. I would do the same as you... double clutch it.

But normally I would avoid doing that all the time. Every once in awhile is ok. But perhaps you can get by just using second gear.

It's the same when I am at a traffic light... I never shift first into first gear. I always move the shifter into 2nd, and then first gear. When you move the shifter into 2nd gear... the trans internals stop spinning - or so I believe. It just feels better to me and my trans. I also go into 2nd before shifting the car into reverse as well. Even though reverse gear is synchronized on BMW's.. it's just a habit I have from my VW days with a non synchronized reverse gear.

Dackel

Bingo! I was taught to always shift into 2nd before engaging first gear. I'm teaching my son to do the same. Sadly, even after so-called "driver's education", he had no knowledge of manual transmission driving. I had to teach him what a tachometer is. When I had driver's ed, they taught us manual, but some inadvisable techniques, like holding the car on a hill by slipping the clutch. I politely told him that is what the e-brake is for! Fortunately for me, my mother was a badass with a stick shift, and she taught me to drive in a 1972 Toyota Corolla four speed.

[Matticus91]

Originally Posted by Dackelone

When you move the shifter into 2nd gear... the trans internals stop spinning - or so I believe.

Hey Dack - genuinely curious; are you saying you move the trans into second gear while rolling, and then once totally stopped you shift to first? That would make sense then, the internals should not be turning if the car's wheels are stationary and the clutch is disengaged/not mated to the spinning flywheel.

[Dackelone]

Originally Posted by Matticus91

Hey Dack - genuinely curious; are you saying you move the trans into second gear while rolling, and then once totally stopped you shift to first? That would make sense then, the internals should not be turning if the car's wheels are stationary and the clutch is disengaged/not mated to the spinning flywheel.

Yes, sometimes. But more often I will just stay in whatever gear I happen to be in... say third or fourth... then, when coming to a stop... I will push in the clutch when the revs fall under say 1,500 rpms... Then while I am stopped... I will put the trans into second gear(first) and then into first gear(of course depressing the clutch pedal).

When you put the trans into second gear, it stops the trans internals from moving. Then when you select first gear... there will be no resistance when you move the shifter into first gear slot. Hope this makes sense.

Also... one should never sit at a traffic light with the clutch pedal depressed and in gear... when you have the clutch pedal depressed... you are putting pressure on the clutch disc and flywheel... in turn pushing the crankshaft forward. Over time... this can wear down your engine's crankshaft thrust bearings.

So... sit at the light in neutral with your foot off the clutch pedal. hopefully before the light turns green, depress the clutch pedal, select 2nd gear and then move the shift lever into 1st gear. This is the best way for long trans & clutch life/wear.

[mackeroni]

Originally Posted by Dackelone

...
One other thing we haven't really talked about... is servicing the trans. Even though BMW says the trans fluid is "lifetime" fluid... I don't believe in that. I've changed my trans fluid four times in 90K miles. To me some trans oil is a whole lot cheaper than a new transmission.

IF you track your car... changing ALL your fluids is needed IF you intend on keeping the car long term.

Dackel

What fluid do you recommend for my manual trans, Dack?

Peace... Mack

[Dackelone]

Originally Posted by mackeroni

What fluid do you recommend for my manual trans, Dack?

Peace... Mack

I am currently using Redline's MTL. But I think I will switch back to Redline's ATF-D4 fluid on my next trans fluid oil change. The trans lever just seems to be clicker with the D4. Redline says for the N55's you can also use ATF-D6 as well, but I've never used it.

Dackel

[jlc45]

Some of the comments and suggestions here are correct and some of them do not have any technical basis. I have built thousands of automatic transmissions and a few manuals and replaced dozens of clutches on a variety of cars. But my knowledge is not current since I am retired. How many of the folks offering advice here have ever even seen a transmission apart? In many instances problems are related to clutch malfunctions and the trans is not the problem. The "internals" of the trans do not stop in second gear. The gears and shafts stop rotating only when the vehicle is stopped and the clutch is disengaged. Like when you are stopped at a light with the clutch pedal in.
(Or the engine is off and the car is stopped. :-) )
The throwout bearing acts on the fingers of the pressure plate moving it "backwards" and when the clutch pedal is depressed the clutch disc is no longer able to "grab onto" the flywheel. The crank only moves forward and back to a very minor extent, a few thousandths of an inch and this has no affect on shifting performance.
There is no technical reason why shifting into second before shifting into first should make any difference. If you think this is important, please explain why. Similarly, there is no harm caused by resting ones hand lightly on the shifter while driving. Again, please explain why you believe this will damage the transmission. Lightly being a key word here. There is no technical reason why you can't skip a gear while shifting. I go from 3rd to 5th quite often and have been doing this for years. It is easier to rebuild an auto trans than a manual in my experience. As I said, I have R&R and completely rebuilt over a thousand automatics. I have seen Fords with no second gear, which shifted from 1st to third and the owners did not even realize they had a problem.
The most obvious reason synchros malfunction is because they crack and lose their ability to grab onto the cone portion of their corresponding gear. In that case the trans must be disassembled to repair the defect.