Changing transmissions from auto to manual in Mazda 6

I’m about to change the engine in my '03 Mazda 6 due to what is apparently a slipped timing chain which has, in turn, probably caused valve damage. The new engine has a perfectly good 5 speed transmission with it and since I prefer to drive a manual drive car I’d like to change that too. Any obvious problems here that my lack of experience is overlooking? Suggestions? Warnings?

I would not do it. There are several pitfalls your going to run into with modern electronic controlled cars your probably not thinking of. And this is on top of the required cutting and possible fabrication work to get the shifter and clutch pedal installed.

Your car has a transmission control module that controls the automatic transmission, and is interconnected with the ECM. Removal of the TCM or not having the TCM connected properly to an automatic will cause you to have a never-ending ‘check engine’ lights. Swapping ECMs probably wil not work, because they are VIN encoded, and the ECM will need to be re-flashed to work properly.

Also, there is the matter of installing a clutch pedal assembly and shifter. A manual transmission doesn’t work without a clutch pedal. Adding one to the car made with an automatic probably means fabrication work. Cutting into the firewall is definitely required, and you’ll need to use extreme care to cut the required holes in the precise location to get the system to work correctly. Same with the shifter hole. These front-wheel-drive cars use a couple of different styles of shifter to make it work, and both will most likely require brackets to be fitted and welded. One uses a shaft connection to the transmission, and requires the shifter mechanism to be attached to the engine so the shifter base can move with the engine as it shifts around. The other uses cables to isolate the shifter from the engine movement, but requires a fairly complex shifter base, again with brackets that may need to be welded in.

I have yet to see a car that was made to be completely ‘bolt-on’ interchangeable between automatic and manual transmissions.

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Make the motor swap with the automatic transmission in place. If the motor is the exact same year and bolts up to the auto transmission you’ll be on your way.

Before starting any work you must check to see if you can use the current electronics in the car with this new motor? A motor set up for manual transmission may or may not have all the same sensors in the same places. Check all your electrical connectors for compatibilty before you get half way into this and find out you have a problem.

Don’t attempt to switch the auto for a manual trans. It is just too complicated. Get the car running with the new motor - sell it - and then buy another one with a manual transmission.

If the replacement motor isn’t from the exact same year you can run into problems, There are slight changes every year in electronics and emission controls. You are already flirting with danger switching a motor for a manual trans into the car body with an automatic trans. If the donor car is just one year newer or older this could quickly get beyond what an inexperienced mechanic could troubleshoot.

Both BustedKnuckles and UncleTurbo have given good, valid advice.
Contrary to what the OP believes, this is not a “plug and play” situation.

For what its worth I looked into doing this kind of thing once too. I asked quite a few people and I couldn’t find anyone who said to do it - that it wasn’t even close to being worth the hassle even if you could eventually get it all straight. So what you’ve gotten above is pretty much what you’ll hear most anywhere you ask.

A simple 3 step process:

  1. Replace engine using auto trans.
  2. Sell car with auto.
  3. Buy car with stick shift.
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If it was something like a 50s or 60s era car, it could be relatively simple, but, as others have said, it’s not worth doing with this new a car. It’s probably be cheaper in the long run to just sell what you have and find a similar vehicle with a stick shift, you may even be able to find a Speed6 with a stick

“I’m about to change the engine in my '03 Mazda 6 due to what is apparently a slipped timing chain which has, in turn, probably caused valve damage.”

Two key words here: “Apparently” & “Probably”… This leads me to believe you do not know what is REALLY wrong with the existing engine…

If you think properly diagnosing your existing problem is difficult, wait until you undertake this engine-tranny swap. I suspect this car will never again move under its own power, but if it does, it will be with the engine and transmission that is installed in it NOW…

As others have suggested, you are setting yourself up for a lot of work with uncertain results. Don’t do it.

I concur with the advice to skip the manual transmission swap. You will be far better off with the automatic.

I did this , from a 99 ford ranger stick to a 98 ford ranger auto. I messed up . I have 13 codes and can’t keep it running . What do I do. You said I could flash the ecm right. Is that all. I placed the neutral safety switch back on harness and now it running but it not good. HELP.

It’s actually quite simple. Remove the radiator cap, roll a manual transmission Mazda 6 under the radiator cap, install the radiator cap on the manual transmission Mazda 6. Done!

My BIL did this to his 62 Fairlane but then he’s a mechanical genius, retired, plenty of money and has a lift and full featured shop.

Good comments above. I do like this idea, from a theoretical perspective anyway. Manuals are way more fun to drive imo. This may be possible, but suggest to not go at with a “damn the torpedo’s, full speed ahead” methodology. You need to do some research, first somehow verify such a thing is possible, and what all is involved. The clutch pedal related fabrication and mounts may be big jobs, but are doable. You could farm those out even. But the wiring harness, sensors, power train hardware and software versions, that’s where the biggest risk lies. And you probably won’t find anybody locally you could farm those out to. So focus on the latter, make sure you can solve that problem before starting in on this. If I had this in mind, I’d probably visit a Mazda dealership shop at a time when they aren’t busy for a friendly chit chat with one of the experienced mechanics there. Bring some donuts.

You will need the auto transmission PCM (ECU) and wiring harness with auto trans connectors. There are multiple emissions packages for each engine and they may not be compatible between the two years, for example a 1998 3.0 liter engine came equipped with 2, 3 or 4 oxygen sensors depending on the specific package. Finding a PCM that will work with your new combination may be a challenge.

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Changing from an automatic to a manual on a modern transverse-engine FWD vehicle is a lot more complicated than it appears. In addition to the tranny itself, you’re also dealing with different halfshafts, linkages, what’ll you do with the tranny cooler, how will you install the new shifter, how will you add the clutch pedal and linkages, how will the TCM deal with the change, and countless other issues.

Could it be done? Sure.
Is it a simple swap? Nope.
Is it cost effective? Not a chance.
Circuitsmith has the best answer.

It was far, far easier in the old days of longitudinally mounted drivetrains and no electronics. But installing the shifter still took some measuring, cutting and swearing.

Switching from an automatic to manual on a car built in the 60’s is magnitudes easier then trying that on a modern vehicle. I did it once to a 72 Vega, and helped a friend convert a 68 Mustang. We had a few hiccups but nothing that difficult.

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PLEASE stop reviving 6-year old discussions

OP had a 2003 Mazda 3

The guy that revived this discussion has some kind of a Ford Ranger

I’ll bet lunch we will NEVER hear from the Mazda guy again

This sites sort isn’t working very well. My most recent list shows threads 5 years old at the most recent.

Nice catch, db.