15 replies to this topic

[luvin_the_rings]

Hey Everybody, 

 

I had my first race as a rookie last month on the 20th at Buttonwillow #13CW.  I must say that is the most fun on 4 wheels I've ever had.  Way more fun than any auto x, or track day.  I got my first taste of the fun, but only a small taste, because I dropped a valve on my 2nd lap of my first race on Sunday.  I have video, but haven't had the time to trim and upload.  

 

Basically what happened is I was heading out of the off ramp section heading towards cotton corners and when trying to shift from 2-3, I was having trouble finding 3rd gear.  I know I am a complete hack when it comes to shifting, and I wasn't being very gently or using correct hand position.  I would always slide it into 5th.  Here is the strange part, even though the gear lever would be in 5th, there was no gear engaged.  It would be like neutral.  But if I went back to 3rd then back to 5th, the gear was fine.  It was like the gears missed or something.  This happened again for the 4th time in the same section, and after I got it into 3rd gear i realized I had a blown engine and got the meatball flag immediately.  I'll post a video when I can. However through my searching on the archives and miata.net, I have found that this is an issue that happens often? Does "neither gear" ring a bell? I didn't over-rev it too bad, maybe just to 7200 rpm, it didn't even hit the rev-limiter, and I could tell the valve broke after I got it back into 3rd.  I distinctly went into 5th gear.  Car has year old mazdaspeed race motor mounts, but the diff mounts are probably older, although they don't look damaged at all.  

 

We found a used 1.6 engine from a front runner for fairly cheap and I would like to know if it is necessary to open the transmission up and have a look at the shafts and gears, (forks?) before mating it to the engine and slapping it in.  I checked the shiftier bushings, and their all good.  We have the updated aluminum bushing from Mazda speed. Its still snug in there. The transmission was supposedly rebuilt right before we bought it.  The cylinder head was a new Drago unit.  I imagine we might have been running slightly lean due to our fuel consumption figures.  (10-12  mins/gal, is that normal for a 1.6?)  Our innovate gauge just had a new sensor installed, but it might not have been calibrated correctly like our last sensor.  There was always a valve tick, even when warm, but only at idol and low RPM.  Could a prolonged valve tick cause a failure like this after two laps of high RPM racing?  I was in the draft but the coolant temp never got above 175 and the oil temp stayed below 200 even in the draft. 

 

I know i'm throwing a lot at you guys at once, but any help appreciated.  Mainly want to know if I have damaged the transmission.

 

Thanks,

 

-Z 

[FTodaro]

Some thoughts to your post. I have over revved higher that 7200 without issues, so either it was higher than that or there was an issue brewing with that motor.

 

On the shifting, If its an old NA box the shifter is not as good as the NB shifter and easier to miss the gate.

 

One thing that is important with these transmissions, is you have to be a little patient with the shift and let the spring loaded shifter find the gate for you. force yourself to use an open palm any 2/3 3/4 4/3 shifts. 

[luvin_the_rings]

It never hit the rev limiter, and It was an up shift so the RPMs for sure didn't go higher than 7200. Is the NB transmission heavier than the 1.6? Are the 1.6 and 1.8 NA transmissions basically the same?

[chris haldeman]

If the engine is running fine just has a burnt/bent valve you could just send it back to drago for a freshen up. 7200 shouldn't hurt anything but lean will burn valves very quickly. If you can afford a new built trans buy one. It is amazing how much nicer they are than old wore out crap

[Pat Mcg]

I kind of like the old wore out crap transmissions from the junk yard...  I have 3 sitting in the garage..  200s buck each from the junkyard.   I agree with Chris.. If you can afford to purchase a built one that's the way to go..  I can switch trans out in about an hour or 2 at the track so I just always bring a spare..   I only use the 94-97 ones though. 

 

No clue what blew on your engine.  Over a dozen things could fall into the "Engine Blew" category..   Probably something minor.  These motors are fairly rugged..  Lean..  Not good on 1.6 valves but that is not a blown engine.  Rip the head off and have a look see....

 

I think the 99 and newer transmission are heavier. Maybe 1 pound...  I have one sitting on the floor..   I should probably check that.  NB trans has a more robust shift tower..  Stick with the 94-97 for a 1.6 IMO..  Better syncros..  .

[davew]

Amazing that the guys with experience (Frank and Chris) say get a fresh trans because they are worth the price. yet the guys with 77 and 8 posts respectively say use junk yard ones. My guess (purely a guess) is that these 2 people have never driven a fresh trans.

 

I personally have rebuilt HUNDREDS of SM transmission. Probably more than any person in the country. In fact I rebuild transmissions for Chris. A new trans is like buying a new pair of shoes, you don't realise how bad the old one was until you get a new one.

 

Your missed gears can be cured by simply letting go of the shifter. Only use 2 fingers for 3-4 or 4-3 and you bump/release/bump for 2-3. Also use a stock shift ball and take out the aluminum bushing and install a plastic one

[Ron Alan]

. Also use a stock shift ball and take out the aluminum bushing and install a plastic one

This advice is worth the price of a checkered flag!!!!!

[luvin_the_rings]

Well, we dropped a valve.

 

 

This advice is worth the price of a checkered flag!!!!!

Meaning its good advice? lol

[Ron Alan]

Well, we dropped a valve.
 
 

Meaning its good advice? lol

Good advice on using the stock plastic bushing and not an aftermarket metal one. After missing 2 shifts that cost my son his first win we found the "never miss a shift aluminum piece" had worn to a sharp edge around the top...2/3mm of slop. When I sent the vender who sold them a picture of what it looked like they seemed concerned...but appearantly not that much because they still sell them!

[Todd Green]

yet the guys with 77 and 8 posts respectively say use junk yard ones.

 

Actually,  the guy with 8 posts said, "I agree with Chris.. If you can afford to purchase a built one that's the way to go."   So he said he uses junk yard stuff, but doesn't recommend it if you have the budget.  Anyway, I regularly drive a car that has a high mileage junk yard tranny and one that has a Bennett tranny.  In 4+ years I've never missed a shift in the Bennett tranny.  I miss several a race in the junk yard (the notorious neutral between 3rd and 5th) one.  If I slow down my shifts with the junk yard one and let the springs do their work, then I don't have issues.  Good luck passing anyone shifting that slowly though, might as well leave it in 3rd for the corner (which is what we mostly do in enduros.)  Obviously YMMV depending on your track(s).  Still, IMO, a good/rebuilt tranny is worth every penny.

[luvin_the_rings]

So are we talking brand spanking new from Mazda, or "Blueprinted" from DaveW or just properly rebuilt by any shop that can measure all the lash and clearances to make sure their at minimum spec?

 

-Z

[FTodaro]

So are we talking brand spanking new from Mazda, or "Blueprinted" from DaveW or just properly rebuilt by any shop that can measure all the lash and clearances to make sure their at minimum spec?

 

-Z

Just my opinion, maybe Dave and others have a different experience, I would rather have a rebuilt transmission over a new Mazda trans, my experience has been the counter shafts in those boxes are softer than the older boxes. Also if you rebuild an older NB box is less money and as good or better than new.

[davew]

I agree^^^^^

 

The most expensive box to rebuild is an NA 1.8. It has all the problems of a NA 1.6 with the expensive 2nd gear syncro.

[SaulSpeedwell]

 

Basically what happened is I was heading out of the off ramp section heading towards cotton corners and when trying to shift from 2-3, I was having trouble finding 3rd gear.  I know I am a complete hack when it comes to shifting, and I wasn't being very gently or using correct hand position.  I would always slide it into 5th.  Here is the strange part, even though the gear lever would be in 5th, there was no gear engaged.  It would be like neutral.  But if I went back to 3rd then back to 5th, the gear was fine.

 

Ultra-worn shift selectors with a possible side-helping of shift rod slop.  Suggest having it rebuilt before something worse happens. 

[SaulSpeedwell]

Just my opinion, maybe Dave and others have a different experience, I would rather have a rebuilt transmission over a new Mazda trans, my experience has been the counter shafts in those boxes are softer than the older boxes. Also if you rebuild an older NB box is less money and as good or better than new.

Agree.  Not sure when the soft countershaft cancer creeped in, but I know it was as early as crate transmissions bought at the Runoffs at HPT in 2006.  I haven't seen enough 2001+ OEM transmissions to have an Internet opinion on those yet, but I am willing to give my opinion that "crate" transmissions after 2006 seem to be the least reliable option.

[Pat Mcg]

Again, If money is no object than a built tranny is the way to go.  There is a reason why the top folks are not using Junk yard transmissions..  

 

The original post the guy is using a used motor as it is....   I just assumed he didn't have an appetite for 1K on a trans...

 

SO, a good low mileage junkyard tranny for a couple hundred bucks, change the seals, dump some redline in; it will get the job done is my only point.