[alexjames23]

Hate to bring back on old thread from the dead, but I have this problem exactly with my 2002 M3.

Here is my thread, as I'm curious if any further information has been gathered regarding this problem as of mid 2017: http://www.m3forum.net/m3forum/showt...p?p=1067708462

[M3Pete]

Originally Posted by alexjames23

Hate to bring back on old thread from the dead, but I have this problem exactly with my 2002 M3.

Here is my thread, as I'm curious if any further information has been gathered regarding this problem as of mid 2017: http://www.m3forum.net/m3forum/showt...p?p=1067708462

My 2nd and 3rd gear synchros are bad on the 6 speed 420g tranny I sourced for my E36 auto to manual swap, so i just took it out and sent it to Metric Mechanic in Missouri. Good reviews and owner has tons of experience with working on these transmissions and has figured out how to make the synchros better than new. I will let folks know how it turns out when I get it back and put everything back together, but it should be good to know that there are options out there besides just living with slow-shifting or 'fixing' by replacing with junkyard trannies--and then finding out what you got isn't much better that what you had. In my case, it would shift fine if slow-shifted below 3500-3800 rpm. Anything above that, no matter how gingerly it was shifted, it would grind. I was using the UUC recipe of Redline ATFs and also had LubroMoly added at the recommendation of UUC. I installed a Stage 2 organic clutch and LW flywheel as part of the swap, and that mix is supposed to keep the gear-rattle noise at idle down. I have done some reading since I removed and shipped the tranny, and now see some posts that say anything other than the BMW-spec fluid can cause the synchros to be too slippery and cause grinding because the synchros don't have enough friction to slow the gears down. Not sure if that is accurate or not, but I never got a chance to try switching the fluid and seeing if it made a difference...

[alexjames23]

Originally Posted by M3Pete

My 2nd and 3rd gear synchros are bad on the 6 speed 420g tranny I sourced for my E36 auto to manual swap, so i just took it out and sent it to Metric Mechanic in Missouri. Good reviews and owner has tons of experience with working on these transmissions and has figured out how to make the synchros better than new. I will let folks know how it turns out when I get it back and put everything back together, but it should be good to know that there are options out there besides just living with slow-shifting or 'fixing' by replacing with junkyard trannies--and then finding out what you got isn't much better that what you had. In my case, it would shift fine if slow-shifted below 3500-3800 rpm. Anything above that, no matter how gingerly it was shifted, it would grind. I was using the UUC recipe of Redline ATFs and also had LubroMoly added at the recommendation of UUC. I installed a Stage 2 organic clutch and LW flywheel as part of the swap, and that mix is supposed to keep the gear-rattle noise at idle down. I have done some reading since I removed and shipped the tranny, and now see some posts that say anything other than the BMW-spec fluid can cause the synchros to be too slippery and cause grinding because the synchros don't have enough friction to slow the gears down. Not sure if that is accurate or not, but I never got a chance to try switching the fluid and seeing if it made a difference...

Awesome, thanks for the info! Let us know how that synchro rebuild goes.

I'm switching to oem BMW fluid and will report back with results. I still have the grinding, but have trained myself to slow shift 2-3 and 3-4 (sometimes will grind as well). I hope I caught the problem early enough.

[mrgizmo04]

Originally Posted by M3Pete

My 2nd and 3rd gear synchros are bad on the 6 speed 420g tranny I sourced for my E36 auto to manual swap, so i just took it out and sent it to Metric Mechanic in Missouri. Good reviews and owner has tons of experience with working on these transmissions and has figured out how to make the synchros better than new. I will let folks know how it turns out when I get it back and put everything back together, but it should be good to know that there are options out there besides just living with slow-shifting or 'fixing' by replacing with junkyard trannies--and then finding out what you got isn't much better that what you had. In my case, it would shift fine if slow-shifted below 3500-3800 rpm. Anything above that, no matter how gingerly it was shifted, it would grind. I was using the UUC recipe of Redline ATFs and also had LubroMoly added at the recommendation of UUC. I installed a Stage 2 organic clutch and LW flywheel as part of the swap, and that mix is supposed to keep the gear-rattle noise at idle down. I have done some reading since I removed and shipped the tranny, and now see some posts that say anything other than the BMW-spec fluid can cause the synchros to be too slippery and cause grinding because the synchros don't have enough friction to slow the gears down. Not sure if that is accurate or not, but I never got a chance to try switching the fluid and seeing if it made a difference...

Just to confirm, Metric is rebuilding your 6 speed 420g tranny or your 5 speed zf tranny for the E36? On their site they list ~$4600 for the 420g...http://metricmechanic.com/ultimate-t...sion-rebuilds/

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[conniem3]

Originally Posted by alexjames23

Awesome, thanks for the info! Let us know how that synchro rebuild goes.

I'm switching to oem BMW fluid and will report back with results. I still have the grinding, but have trained myself to slow shift 2-3 and 3-4 (sometimes will grind as well). I hope I caught the problem early enough.

I have the same issue as everyone here, switched from Redline to Ravenol. Didn't really help the issue at all, but all other gears are smoother ¯\_(ツ)_/¯

I've heard that the tensioner spring (or something like that) could be the culprit, which is like a $5 soring, except you have to drop half the tranny or so to get it out and check. Some say that fixed the issue entirely, others not. At that point, if you don't have a transmission lined up it's a waste of labor.

I know TM sells the 420gs too with a core refund, but that's still about $4K. The most reasonable route for me will be to purchase a SMG trans and re use my 6mt bellhousing for the swap. Seems most cost effective and SMGs are usually more healthy than used 6MT even if they're low miles.

Wish there was a way to do surgery on these and replace only the synchro...

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[M3Pete]

Originally Posted by mrgizmo04

Just to confirm, Metric is rebuilding your 6 speed 420g tranny or your 5 speed zf tranny for the E36? On their site they list ~$4600 for the 420g...http://metricmechanic.com/ultimate-t...sion-rebuilds/

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I had an auto and swapped it to the 6 speed 420g since I have a 3.38 rear. I had a '97 M3 sedan with the ZF five speed and it was a smoother shifting trans, but on the highway, it always felt like it was missing a gear, so I figured I would go the 6 speed route. Maybe not the best idea in hindsight. The trans was a lot more costly to source, and now that I am having it rebuilt, my budget is WAY blown. But I will have an essentially new 420g (some say better than new, with the improvements Metric Mechanic has made to them) in my Hellrot Red '99 convertible when done. And since my car only has 56k on the clock, it should be the last thing I will have to worry about going forward. While they have it apart they are putting the a Euro E36 M3 input shaft in it which will make it the same size as the E36 (vs the larger E46 M3 input shaft it had while it lived in a US M3). We will see how it all turns out....

BTW, one thing I will say is removing the tranny, clutch, etc. the second time is a lot easier and quicker than the first go-round. Not that I want to do this a third time, but just sayin'!

[mrgizmo04]

Originally Posted by M3Pete

I had an auto and swapped it to the 6 speed 420g since I have a 3.38 rear. I had a '97 M3 sedan with the ZF five speed and it was a smoother shifting trans, but on the highway, it always felt like it was missing a gear, so I figured I would go the 6 speed route. Maybe not the best idea in hindsight. The trans was a lot more costly to source, and now that I am having it rebuilt, my budget is WAY blown. But I will have an essentially new 420g (some say better than new, with the improvements Metric Mechanic has made to them) in my Hellrot Red '99 convertible when done. And since my car only has 56k on the clock, it should be the last thing I will have to worry about going forward. While they have it apart they are putting the a Euro E36 M3 input shaft in it which will make it the same size as the E36 (vs the larger E46 M3 input shaft it had while it lived in a US M3). We will see how it all turns out....

BTW, one thing I will say is removing the tranny, clutch, etc. the second time is a lot easier and quicker than the first go-round. Not that I want to do this a third time, but just sayin'!

Nice. Given Metric's price, have you looked into Turner's offering at all?

Yeah, you def get faster at doing them, lol.

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[forzanerazzurri]

The third gear grind is always interesting to hear about. My third gear is probably my smoothest gear. Running oem fluid. Its second that is notchy for me and even then it's only at low rpm shifts. If im flying the whole gearbox just rows like butter.

[dothraki]

Originally Posted by forzanerazzurri

The third gear grind is always interesting to hear about. My third gear is probably my smoothest gear. Running oem fluid. Its second that is notchy for me and even then it's only at low rpm shifts. If im flying the whole gearbox just rows like butter.

Same. My 2nd grinds mostly at low RPMs and at low speeds. 3rd is fine.

[HassanEido]

Originally Posted by forzanerazzurri

The third gear grind is always interesting to hear about. My third gear is probably my smoothest gear. Running oem fluid. Its second that is notchy for me and even then it's only at low rpm shifts. If im flying the whole gearbox just rows like butter.

Same here