2010 Hatch Sport 6spd MT 1st to 2nd issues

edgibbon679 said:

I've been driving my hatch for about 6 years now, purchased at 70k miles, driven like a father who can't afford another repair most of the time. In my time with the car, I've had the transmission rebuilt at the dealer through the warranty I originally purchased at around 80k because it refused to shift in to 2nd gear. I then had the transmission essentially explode while on the highway when I down shifted for slower traffic at around 100k (was maybe around 4k RPM, nothing crazy). Was able to baby it to the closest shop I could find and they sourced a used transmission for a repair. This was 2 years ago so no warranty left on the repair.

The problem: if I'm not babying the shifts, I am getting a grind occasionally going in to 2nd gear again. Anything over 3k RPM is a gamble. I also get a weird whistling noise in 6th on the highway. It feels more like my clutch isn't quite as engaged as it should be but its only these gears. I'm really not in the mood to be sitting on the side of the highway with my toddler again so I'm staring down another transmission repair because most everything else about the car is in great shape.

I've done plenty of other repairs but never a transmission but I'm thinking of rebuilding this myself. A couple of things I need to know:
1. what model years are compatible with the 2010 6spd mt? I'm pretty sure the 2012-2013 skyactive transmission is similar
2. If yes to above, what parts if any did they update to resolve issues? I've read about syncho issues and some updated clutch control arm (or something, its been a minute) which sounds like it may be the culprit
3. If I'm going to rebuild this transmission with the expectations of getting another 5-8 years with this car, can somebody please recommend a rebuild kit and anything else I need to look for.

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Sorry to hear about your transmission problems - The 2010 and 2011 Mazda 3 hatchbacks were identical vehicles except tire size and a few cosmetic things ( bumper , spoiler ) . The HBs only came with an NA- 2.5 ( except speed 3 ) and the choice of a 6speed manual or 5 speed auto w/sport shift.
I have a 2010 HB, which I purchased new and now 14 years later still have it running very well with 148,000 miles. - It is an automatic 5speed with sport shift not a manual like yours . Since I have done most all maintenance myself , Ive had countless interactions with different dealers parts depts and service depts who will usually print 3D diagrams for different areas of the car . Mazda dealers are pretty helpful to DIY people - That said I was exposed to a few recalls which occurred in 2010-11 ,,,the rear hatch hydraulics and a seat belt issue - except......There were selective recalls done on the 6speed manual transmissions which were notorious for running great for a year or so and then kaput - I dont believe Mazda ever had a full recall on the manual trans - but owners that came in and were persistent got the rebuild ....and honestly I heard from owners that said it was ok and others who said it just failed again 20K later as the design was inherently flawed - Its to bad because its such a spectacular car and the engine is extremely well built and estimated to run 300K with basic maintenance. So after all that ...Ive babied my transmission and done a drain and fill every 35K miles . Its runs like the day I purchased it - I at one point loved my car so much ..I callled Mazda to check on the inventory of Manual and Auto transmissions for that year - Mazda told me NOT to switch my auto for a manual-- enuf said - This was 3 years ago and Mazda had about 5 new auto transmissions for the 2010-11 Mazda 3 2.5 in inventory in North America ( all dealer parts depts can access these) - It was $4000 - I decided to just ride out mine and see how long it would last before shelving a new unit in anticipation of a failure.
The automatic has been a solid transmission if you take good care of it and it shifts very smoothly and has only had the TCM fail at 120K which is fundamentally just a junction chip which commands the shift points etc . That was about $450 but easy to swap out -I did it in 30 minutes - My suggestion - Read the reviews on the 2010-11 Mazda 3 HB and you will see the car was a hit and anyone who sold it or wrecked it misses it very much- The values on used models is very high -- You have low mileage and I suggest dropping a 5speed auto in and drive it for another 150K -( minimum) This depends on the overall condition of the vehicle of course - But a new $4000 auto trans makes the car a seriously reliable car which is likely going to run many many more years - Heres motor reviewers take on the MZR 2.5 engine which we have -
Mazda MZR 2.5L 5L-VE Engine Specs, Problems, Reliability, oil - In-Depth Review (motorreviewer.com)
If you drop yet another manual rebuild in that car ....the odds are high it will not be the last repair -
Best