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Gearbox problem?

Old 06-25-17, 12:30 PM
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Gearbox problem?

I was driving the car in traffic and the car make a clunking noise. It was otherwise driving and shifting perfectly this morning during 3 hours of country driving.

Now it's almost impossible to change gears (can't get into reverse or 1st gear) and the clutch makes a vibrating noise when I try to put it in.

Is the gearbox overheated or the clutch gone? I'm going to leave it for about half an hour and try it again... the car is stuck halfway out of my parking spot in the parking garage.

Waited half an hour and its the same. I can't shift into any of the gears... is it the clutch? I think I'm going to have to get it towed out.

Last edited by HiWire; 06-25-17 at 01:05 PM.
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Old 06-25-17, 03:23 PM
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The tow truck driver said there might be something wrong with the clutch or the clutch cylinder... the gears will change when the engine is off, but the clutch only engages when the pedal is all the way down.

He said they'll need a flatbed to tow the car.
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Old 06-25-17, 05:53 PM
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It sounds like a clutch issue to me as well. A guess, but with the 'clunking' and vibration I'd suspect a pressure plate issue.
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Old 07-27-17, 04:29 PM
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The dealer is replacing the whole clutch assembly. It's expensive, but at I'll have the comfort of knowing everything will last for a while.

I learned a couple lessons from this:

1. Don't drive the car back to an underground garage if it's having driveability problems. It's easier for tow trucks to assist you if the car is at the side of the road or in a parking lot.
2. Use a flatbed truck if possible when towing an FD. The cars are low enough that they could take damage from a conventional towing truck. Also, a driver should use dollies for the wheels on a conventional tow to prevent damage.
3. A clutch can fail without any symptoms. The car was driving and shifting perfectly before everything went to hell, so it might be a good idea to replace your clutch earlier rather than later.
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Old 07-27-17, 04:39 PM
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You took it to the dealer


If it's a '93, it might be your clutch fork. They were prone to fail and were upgraded in '94
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Old 07-27-17, 04:53 PM
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BC Fork it out.

We've had a couple broken clutch forks locally here that displayed those symptoms.
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Old 07-27-17, 06:21 PM
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I asked them what the specific problem was, but they were coy and just said they had to replace the entire assembly. Normally, I would have taken it to my mechanic, but he was full up and the problem couldn't wait.

Adios, ACT clutch... I wonder if the new stock clutch will have a lighter pedal feel?
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Old 07-27-17, 08:49 PM
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Originally Posted by HiWire View Post
they were coy and just said they had to replace the entire assembly
To me a statement like that is a big red flag. Regardless, there's something amiss which requires removal of your transmission. That'll be the bulk of your cost, especially at a dealer.

And if you didn't like you clutch before whatever broke broke, then you'll have the opportunity to replace that even if it didn't need replacing.

The stock clutch will have a lighter pedal feel. Do you know if you were running a puck clutch.

And if the clutch fork is a '93 and it's ok, you may want to replace it for peace of mind.
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Old 07-28-17, 11:22 AM
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I think it was the ACT ZX6-HDSS - HD-M (the Stage 1 Heavy Duty) with the full-face friction disc.

I'll ask them if they replaced the clutch fork... they said they were still waiting for some parts yesterday.
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Old 07-28-17, 04:59 PM
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Did you even open up the trans inspection port and look in as someone pressed the pedal down? That is always the first thing to do if you are worth owning a FD.

Never even trust Mazda mechanics as they are not that good with RX-7s.
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Old 07-28-17, 07:12 PM
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Think the same people that take their cars to the dealer are the same people that don't open the transmission inspection plate. That's not a knock by the way. There's just people that don't want to deal with the mechanics and prefer to enjoy their cars.

Back to the transmission. If you search on clutch fork, it seems there's a number of posts with ACT HD pressure plates and busted forks.

And back to busting on dealers. I drove my FD to the dealer once, and the sales people looked at it and asked me what it was
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Old 07-29-17, 09:20 AM
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Again +1 on the clutch fork. Can't remember for sure, but I think they're were ~ $90 or so last I looked. Not sure how much the dealer might nick you. Regardless, a lot less than the labor to R & R your transmission again if the clutch fork breaks from fatigue with the slightly stiffer pressure plate. If you really want to go all out, new pilot bearing and seal and resurface the FW.

And my .02 on the dealers...
With a few exceptions most techs at a dealership have never even seen under the hood of the FD or any RX7 for that matter. Hell the last rotary was offered in 2011, so it's been off warranty for 3 years or more. And the FD is OBD 1 on top of everything else. So I'd be reluctant to let them diagnose anything under the hood. If you can't DIY, find a specialty shop near you.
Not so with the driveline though. Nothing aft of the engine that should cause head-scratching to any decent dealer tech. Their flat-rate can be a shocker but if they're trusted it might be worth it to some.
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Old 08-20-17, 01:00 PM
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So I got an OEM clutch (I assume that means an Exedy). It's taking a while to get used to the much lighter and lower engagement... are my left leg muscles going to atrophy?

How many people like the stock clutch? I think they kept the flywheel, so I'm taking it easy with a 500 mile street driving break-in to allow the surfaces to mate properly.
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Old 08-20-17, 10:13 PM
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Stock clutch is good for stock HP (not sure Exedy is OEM though). Did they replace the flywheel with stock as well?
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Old 08-21-17, 12:14 PM
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I think they kept the flywheel (which is a lighweight one installed by the previous owner) – that's probably why I'm adding a little more gas to keep things matched up when shifting – less inertia.
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Old 08-22-17, 02:59 PM
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Sounds like the clutch fork, slave, master, or line let go. If its the hydraulics I replace all 3 together. A new fork should be the updated style. If you are anywhere near 300 whp a stock clutch won't last. I'd stay with the zx6hdss. If it were me I'd pull it from the dealer and take it to a reputable rx7 mechanic in your area.
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Old 08-22-17, 05:43 PM
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Sad story – the local RX-7 garage just closed for the owner's retirement! Fortunately, there's a bunch of knowledgeable rotary guys in the area so I can probably find help as long as there is enough notice.

My Greddy boost controller has 2 boost settings, Low and High. I'm keeping it at the Low setting right now (the dealer ad claimed 320 hp), so it's probably near stock power levels.

I've driven the car for about 5 years, including 2 track school sessions for Time Attack and some lapping. The previous owner raced the car in Time Attack and he is also a track instructor.

So I figure the clutch didn't owe me much – it never gave me any trouble and I try to match revs whenever I shift (no drag starts). I'll probably go back to the ACT, as suggested, but I'll try to keep this stock one going for now.

My next problem is emissions – I'll have to find a way to get the car to pass for license renewal next year. It's probably a tuning issue as the emissions garage said the car is dumping gas into the system at idle.

Last edited by HiWire; 08-22-17 at 05:48 PM.
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Old 08-23-17, 01:57 PM
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I have the ACT HD pressure plate and find it's a little heavier than stock, but not much. If you were running a super light flywheel, that could have contributed to drivability issues. I am running a 12 lb flywheel and find that's a good compromise.

As for emissions, there a wealth of info on the site, but basically you need an air pump and cat to pass most smog checks.
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Old 08-23-17, 04:41 PM
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The flywheel is probably the lightened street version (my notes from the dealer indicate it might be a Mazdaspeed part). I haven't had any trouble shifting with it on the street or on hills.

We noticed at the garage that the air pump is working and there are two cats on the pipe. The mechanic said that it is running rich at idle, before the cats heat up, which is partly why it is failing the test.

I'll contact the tuner to see if he can create a profile that will pass emissions next year. It is street ported with a Power FC – most of the guys I have asked said it should be able to pass.
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Old 08-23-17, 08:53 PM
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Make sure the cats are good and hot when you get tested.

And is your fuel evaporative system still intact? It can dump fuel/vapor via the purge solenoid at inopportune times. Some have recommended draining the catch tank under the throttle body just prior to the test

Good luck
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Old 01-03-19, 12:06 PM
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So the FD is on a hoist again. My mechanic sent me pictures of the broken clutch fork (he ordered the new one, N315-16-520B). If this was the original clutch fork, it owed me nothing. The previous owner raced it in time attack with an ACT clutch and the Mazda dealer replaced the clutch with an OEM assembly (but not the clutch fork) in 2017.

You can see one of the arms of the fork has broken off completely in the second picture.




Last edited by HiWire; 01-03-19 at 12:16 PM.
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