6 speed lost 4th
 

I made a pull through 1st, 2nd, 3rd, 4th, and then missed the 5th gear shift. After that 4th gear is just gone. Even with the car turned off it won't go in 4th. It doesn't grind or anything, you can feel the gate(?) a little bit but the shifter won't fall in place. Other than that the transmission seems to shift fine into any other gear and doesn't make any weird noises.

Any thoughts on what the issue or solution may be? I'd hate to think I just killed my 6 speed, but I know 4th is the weak link. I guess the most logical step is to drain the fluid and see what comes out, but figured I'd check with you guys first.

6 speed lost 4th
 

Sounds like a bent fork, not stripped gear.

Depending on your resources fixing it can be as expensive as getting a new box.

Depends of course on how cheap you can get a good box and how much you would do "while having it open".

Fork

ISC Racing in Auburndale / Haines City area of Polk County is a spec Miata shop and also rebuilds the transmissions all the time. He has a lot of experience with the 6speed boxes from the RX7 and RX8 race cars he keeps running for other people. Mike Van Steenburg or something is his name. He has rebuild parts and spare pieces stacked up.

Looks like 3rd and 4th are on the same shift fork, you think if I slam it into 3rd real hard I could bend it back the other way? :eggplant:

I take it this isn't something I want to try to fix myself if I have no clue what I'm doing? I'm assuming the cheapest solution is to just find another 6 speed to swap in and resell the broke one really cheap. Thanks for the help, I was really hoping you guys would give me some simple fix.

Gearboxes are a bitch, lots of people can slap a stock motor together and have it work like stock, many fewer for manual gearboxes.

I don't think so. (I have never rebuilt a manual trans though)

I would pull the shifter and inspect for anything out of place. I've had a bolt come loose inside the trans that holds the cast iron piece that the shifter ball drops into. Actually there's one on both ends, and each has vibrated loose on my 6 speed. Made shifter loose and hard to hit gears. Long shot, probably not your problem, but easy to check.

I've done many 5 speeds, no problem.
6 speed I hear is a completely different animal though.

I pulled the shifter and nothing looked out of place, thanks for the tip Pat.

Also managed to dig up a 6 speed repair manual online and I definitely won't be doing that. I've seen a bunch of cheap 6 speeds popping up for sale lately, probably just cruise around with my new custom 5 speed until I can find a good deal.

Thanks for the input guys. I'm even more depressed to know I broke with my shitty driving rather than by making power.

Could you send me a link/copy of the manual you found?

Download here:
Download 6speedtransmissionmanual.pdf

I had a shifter bushing split & migrate inside the turret. I couldn't get into odd gears, as the bushing was preventing the shuttle from going full travel aft. It felt springy/spongy when you tried to get it to engage in gear.


keep in mind that because of the pivot geometry of the shifter, the shuttle the shifter indexes into is always moved in the opposite direction of the handle of the shifter, so the shuttle should be in the fwd position when in 4th.


Try shifting into 1st, 3rd or 5th so that the shuttle is in the rear position, then siphon out the gear oil. take a look at the fwd volume in the turret where the travel path of the shuttle would be when it was in 4th. It can help to take a screw driver and play with moving the shuttle around with the shifter out so you can see what the shuttle is/isn't doing. Maybe there's a chunk o' junk visible? As Patsmx5 mentioned, it's a long shot, but a free.99 fix if you luck out...

id just swap in a 5 speed for the immediate time. i just finished putting a 6 speed back together. it wouldnt shift at all. shafts spun fine though. i spent some time going though it and followed the mazda manual. it mildly daunting until you get it apart and then it all makes sense. my issue was was just a stuck steel ball on the shafts. pretty cheap fix. just took time and a sharp leaning curve.

Easiest solution was to buy a NB that already had a 6 speed in it.

I'm parting out the NA, it was a junker anyway. I'm swapping over the parts that will swap and selling the rest. Attempting to repair the transmission myself was way over my head and I didn't want to dump another $600 into a beat up rustbucket.

I'm not going to ship it, but if anyone local (SW FL) wants the no-4th-gear-6-speed for cheap shoot me a PM.

Sooo what you're saying is Trannys are your specialty? :giggle:

You could at least spell it right

i have the oem 6 speed from my msm. previous owner screwed up second gear (unsure of the issue) and then swapped a 5 speed into the car cause it was cheaper. I got the 6 speed tranny when i bought the car. I have no intentions of rebuilding the stocker and its only going to take up space in my garage. You could piece the two together to have one working tranny. PM me if you have any interest.