Silverstone

Let this be a lesson to you. Never let anyone drive your 7 except your mechanic. At least then you know if he breaks it he can fix it. I recently let my friend drive my 7 with me in the passenger seat. Well to make a short story he ended up grinding the gears at fairly high rpm and now a once perfect transmission grinds from 4th to 5th only. Does anyone know what might be the problem? What would be the best and worst case scenarios in terms of cost to fix the problem. I need to fix this. If I need a new or used transmission, what do these things go for?

Broken09

iTrader: (1)

Common problem if you search you'll find the 5th gear synchro is weak.

Sgtblue

iTrader: (16)

I think it was mostly an issue with the 93 models. If you can do it yourself, it's not terribly expensive, but you have to drop the transmission to do it. As Broken09 mentioned, just do a search and you'll find alot of info.
http://mahjik.homestead.com/files/ho...o/synchro.html
^This should get you started. Good luck.

silver_7

yeah.....mine was the 5th gear syncro.....dont let it go too long or it will be more expensive in the long run.

Silverstone

Thanks for the responses. Makes me feel a lot better that I probably do not need a new tranny. Don't think I'll be able to do it myself if I need to drop the tranny. But I'll let my mechanic know about the year 93 weak syncro thing. You were a big help to my peace of mind.

Larz

Try dumping the fluid and switching to a full synthetic like NEO or Royal Purple. It works wonders.

level7

iTrader: (3)

Hey Silverstone, you may find this thread worth reading regarding your best options.

Cheers

https://www.rx7club.com/forum/showthread.php?t=490367

Silverstone

Ok, I decided on the re-build option. I'm using a specialty shop called Mazdas Plus in Sacramento CA. Basically all the labor and cost is in pulling the transmission and taking it apart. I'm having all the synchros replaced, all the bearings that need to be pulled replaced, the shift select spring gizmo, and misc other parts as needed when they open it up. In addition I'm having the gear oil replaced with Royal Purple synthetic at the suggestion of Larz.

The whole job is going to cost about $1700. It's expensive but I prefer rebuilding using all the upgraded parts rather than buying a used transmission where I don't know what's in it. I hope this is the smart thing to do. This car has costed me a fortune. Even though i've only got 46K miles on the car, when I purchased it, there were major cost repairs that needed to be done. One was a coolant leak underneath the turbo from a metal pc of pipe. Cheap part but lots of labor in removing turbos etc.

BTW, this type of leak is caused by extensive sitting with the same coolant. What happens is that the coolant has a tendency to become very acidic especially in the RX-7. It happens because the engine is contructed like a battery with sandwiched layers of different metal. Be sure to change you coolant every year to avoid this repair.

Then I tackled the air conditioning. Some num nuts along the way, before I owned it, put the wrong oil in the thing which was incompatible and caused the whole thing to gum up and form a concrete material in all the parts of the AC. Had to replace every single part and it cost $3000 to fix it properly.

pr0k

Man, for $3000 I'd just go without AC. I guess it depends on where you live. Good luck with the car in the future.

Silverstone

Funny you should mention that. That's exactly what I did for the first 5 yrs I have owned the car. Bought it in 2001 and decided that I really didn't need to have AC and that I would just avoid driving it in hot weather. Well in the summer it gets pretty consistently in the 90s in the Sacramento area. There were times when I was forced to drive it in these conditions and it wasn't fun. Of course now I am trying to sell the thing and I want to sell it as a "perfect" example of an RX-7 and command a premium price based on the low mileage and condition. That wasn't going to happen with a bum AC and then on top of that to have a bad 5th gear syncro. So I have had to bite a few bullets lately. The thing is now I have a new AC and basically a new improved gear box; I think I may keep it But if anyone is interested I'll take $18,000 for it. Any less and I'm bound to just keep it for a few more years babying it, and see if the supply thins out and the demand picks up.

kraked

Silverstone, you're the dood with the silver FD I saw at Mazda Plus. I had the black FD with the small oil leak.... Anyway, although Mazda Plus knows what they are doing, they are kinda expensive. You may want to talk to Ben (karack) and talk to him about the tranny rebuild.

Silverstone

Please tell me how to get in touch with Ben Karack. It's too late for this job because the 7 is already at Mazda's Plus with the tranny pulled out and apart. But in the future I may want to check out alternatives if I need any other major work. I agree that Mazdas Plus seems to be expensive but I know they do good work and I trust them. I didn't think there were any other good rotary mechanics in the area so would love to have more names. I used to deal with a shop called "Checkpoint Systems". They went through ownership changes and eventually went out of biz. They did all my mods. Mazdas Plus did all my repairs including the coolant leak and the AC system rebuild.

So when were you there? I had the AC done last month and this month the tranny problem happened so it's back in there. I did not notice your black FD either time but I was pretty focused on my problems.

kraked

I THINK that was you.... it was a while ago. Anyway PM "karack"--he runs is own shop up in Marysville and does great work as well.

Silverstone

It may well have been me. I was there I believe about early march this year for the AC job. The AC job was big and it took awhile for them to locate all the parts (about 2 wks).

Anyway if you get a chance to post any more info on that mechanic in Marysville, I'll look him up. It's hard to find good mechanics experienced in working on RX7s. Is he a member of this club?

kraked

Yup, his rx7club forum name is: "Karack"

FLA94FD

Wow that is way too high, you should shop around. My rebuild was around $700 with damage to the output spline.

Also if it the 5th gear syncro change the fluid and live with it. Unless you're speed shift into 5th you not going to hurt it much more. I drove mine around for 4 year like that and the mechanic said 4th and 5th looked fine. 1st and 2nd had some wear but not enough to justify replacement. Also while improved, the 5th gear syncro is still one bad shift from breaking.

Silverstone

I know of no other shops withing 1.5 hrs (or more) driving distance. They are really doing a thorough re-build so if they are a little expensive at least I am getting some new parts put in. The new spring gizmo on the gearshift is supposed to keep you from missing 3rd.

Ok, I know you're right about just living with it but I am planning on selling the RX-7 within the next 6 mos. and I feel it will command a higher price if there is basically nothing to do to the car (except elective stuff). I've got it up for $18,500 because of the low miles but I may have priced myseld into keeping it. I'm so torn

Silverstone

Ok, my mechanic at Mazdas Plus in Sacramento just advised me of what he found after pulling the tranny out and taking it apart.

Basically the 5th gear synchro was cracked but not broken all the way through. So I told him to just go ahead and put it back in and put it back together.
Just kidding

No it was cracked and his plan was to replace all the synchros since he had it apart. The shifting fork looked very good. He also believes in replacing any bearings that had to be pulled. He checked the clutch and found that I had about 30% left on it so recommended that this would be a good time to replace that at no extra labor charge. The clutch itself is only about $335. So I said ok to everything and told him to use Royal Purple for the oil. I'm thinking about giving the damaged synchro to my friend the next time I see him.

So lesson learned and now I really feel like keeping the car longer instead of selling it but money talks so I will see what happens. Not too bad I guess. If I hadn't bought the car with 3 hidden problems (the AC and the coolant leak and the stereo problem) this would be the only major repair needed on the car. Now I basically have a whole new manual transmission. Cool!

Sgtblue

iTrader: (16)

Good to hear. But go easy on your friend, eventually it would probably have gone anyway.

overkill

For good future prevention, try installing a good aftermarket short shifter. Once installed, I NEVER had a grinding issue where as before I had to be mindfull as to how I shifted or I would scratch during shifting. FWIW, I installed the Gotham short shifter, which is a knock-off of the B&M short shifter.

axr6

The 5th speed synchro on my present FD is grinding, as well. I have no plans for replacing it. For fast driving I hardly ever use fith gear in my FD. For leasurely cruising I simply push out the clutch and wait a 1-2 count for upshifting into 5th, enough for the engine RPM to drop to match up with the transmission shaft speeds. This way there is no grind.

As to speed shifting, if you have to, you're probably better off slamming it into a non-synchrozed gear as fast as you can. It is the time of engagement that wears on the gears. It has been shown with racing transmission that the faster the gear engagement, the less wear you get on the gears. There, we're talking about straight cut gears with no synchros and up-down shifting WITHOUT using the clutch. An electricallly or hydraulically operated shifter (F1 technology) produces far quicker gear engagements and far less wear on gears than the fastest operated manual shifter. Naturally one has to realize that the gear ratios in racing transmissions also tend to be far closer to each other vs. in street cars.

BTW - if you wonder, many racers check and rebuild their trannies after each race weekend. I once bet some racers that I could get a full season out of my tranny in Formula Mazda without rebuilt (12-14 race weekends). This was because I blipped the throttle during downshifts (without clutch) to match RPMs, while many racers don't. I won the bet, my dog rings (take the crash load) survived for a whole season and after I sold the car and the buyer took it apart he ended up reusing them. I was quite proud of my skills to drive without abusing the car.

riptor

i have the syncro issue as well...planning on doing the rebuild my self....but if i can find someone to do it for 700 bux than **** ill take that any day...

TMadlem84

I'm having the same problem... while I will eventually fix it... will driving it, staying in gears 1-4 hurt anything? I read someone said if you don't fix it & just let it grind while shifting, it can make things worse, but if I don't use 5 unless I have to... will I be okay for now?

axr6

Well, DUH! Grinding make for wear in metals.

You can choose staying in 4th gear, your engine will simply rotate faster at any given speed but, probably fine and not going to overheat. It is just going to be louder for freeway cruising and wear the engine slightly faster.

As to the transmission, I bet that I could drive a transmission without a synchro ring between 4th and 5th for 100,00+ miles, simply by doing what I posted above. Push in the clutch, count to 1- 2 and shift into 5th. Once you get your timing down, you'll never hear a gear grind again.

In my car the tranny only grinds for upshifts. But in case you have grinding on downshifts, as well, you can do either of two things.

1) Learn the secrets of heal and toe shifting, combined with double clutching and matching RPMs properly and avoid grinding this way. This is the ultimate way to extend the life of your synchroes and be able to drive fast around corners and always be in the right gear.

2) Far easier; just avoid a 5th to 4th downshift, let the car slow enough where you can shift into 3rd where you have good synchros.

I simply consider a waste of money to rebuild a tranmission if that is the ONLY problem with it.

TMadlem84

Yeah, I usually don't need 5th except for highways, which I don't use much. But I'll try the counting to 2 trick... I noticed if I wait when going from 4-5, it sometimes doesn't grind... maybe I just need to work on my timing.