UnknownJinX

So I was enjoying my RX-8, and as I was showing off to my friends, I decided to redline it in 1st and then directly shift into 3rd. Unfortunately, I moved the **** a bit far to the right and ground the 5th gear. I corrected the mistake as soon as I heard the grinding, but now every time I shift(doesn't matter if it's an upshift or downshift) into 5th above about 64 km/h(40 MPH), the gear seems to grind a bit before it engages into 5th, and I made sure the clutch is firmly pressed down all the way. The **** moves easily into 5th when the car is idling stationary or moving below 40 MPH with the clutch depressed, though.

From what I gathered here by searching, I know the following info:

- Early Series II had weaker 5th and 6th gears. Later ones(post mid-2010 I think?) improved in strength.

- The synchro on FD RX-7s can get broken easily by mis-shifting into 5th rather than 3rd.

So my question is:

- Can a fluid change possibly remedy this? I am getting a MT fluid change and differential fluid change next week.

- How much am I looking at if I need a new tranny?

- Independent shop or dealer? There is a local independent shop that seems to be pretty good.

Thanks for any suggestions!

rotaryifidel

I get a slight grind in most gears.

9krpmrx8

iTrader: (46)

Bad synchros are pretty normal for those who don't drive stick correctly so it happens over time. New fluid may mask the issue for a bit but it will be temporary. The series II Rx-8 has a much better transmission so many swap to that for $1000-$1200. You can get a used a Series I trans for $400.00 or so but you may run into the problem on that transmission. Rebuilding them is not worth the hassle.

UnknownJinX

Yikes! That doesn't sound good. My 18-year-old Corolla doesn't even have gear grinding.

Thanks for the info.

I am still relatively new to driving a manual. I never really tried to skip gears on the Corolla before. I was skipping gears to quickly.

Mine is a 09, but it's the one with the old synchro design. There are newer synchro for 5th and 6th gears available.

I will see what happens after I get the new fluid in there. If the grinding continues, I think I may just get a shop to fix it and put the updated synchroes in there.

Greasyman

Mine grinds only down shifting, but I find double clutching helps a lot. To double clutch, from fourth or sixth, put the shifter into neutral, let out the clutch, blip the throttle to about the rpms the engine will be at when it's in fifth (it's a feel thing) then shift into fifth. Double clutching used to be common when cars didn't have synchronized trannys.

9krpmrx8

iTrader: (46)

This would be the first grinding issue I hear on an S2. I do know there is some type of shifter adjustment in the factory service manual that you can do, you might want to look that up, I believe user, Teamrx8 had a thread on the topic.

TeamRX8

iTrader: (25)

Shifting from 1st to 5th is no issue other than it seems odd to not go into a over & pull-back gear like 4th or 6th instead. Over & up into 5th like you tried to do requires more skill. Not criticizing you but it sounds like you just muffed it up doing it that way. Sometimes I muff up a shift on my Civic Si on the street just being lazy or not paying attention by letting the clutch out a bit too soon before the gear was fully engaged. It happens, but the S1 trans is so fragile you could have rung the synchro teeth excessively or possibly bent a shift fork. At a minimum the oil needs to be changed, but you also need to verify both the clutch pedal for the potential failed bracket welds (never had it happen on mine, still have the original pedal from the factory, but there is a TSB and many noted failures here on it) and then the clutch pedal adjustment needs to be checked if the pedal mount is ok.

I very strongly recommend the Ford Motorcraft 75W90 GL4 trans oil for the RX8 manual trans as noted in this thread:

https://www.rx8club.com/series-i-tec...-159398/page7/

good luck with your situation

boricua13

Most Mazda dealers carry the Motorcraft tranny oil for about $20 a quart. If I'm not mistaken, S2 needs 2.2qts

UnknownJinX

I know the S2 manual gearboxes went through some updates.

I believe my car has all the new parts above the green line, but not the ones below, so the synchro rings might be similar to the ones in S1 manual gearboxes.

And yes, I think I should try a 1-4 shift if I redline in 1st. I learned that I can take my time if I need to skip gears - takes a little bit of time for the engine to lower from 9k RPM to 3k RPM.

I grabbed myself a bunch of Redline stuff since it got some praises around here. I will see what happens after the fluid change tomorrow.

TC4Tay

Bought mine with a 5th gear grind, part of the reason I got it really cheap. Apparently the '09s still had the weaker synchros.

Steve Dallas

If you are going to be skipping that many gears, you need to get very good at rev-matching, unless you hate your synchros.

Skipping from 1st to 4th really makes no sense in any context. I always use at least one intermediate gear, and rarely skip more than one gear.

TeamRX8

iTrader: (25)

Sure, abuse your synchros even more using Redline

TeamRX8

iTrader: (25)

9k was right; my bad memory. There is an S2 trans adjustment that originally wasn't a Mazda procedure that I think they added later, but didn't think of because I had missed that this was an S2 trans, not S1:

https://forum.miata.net/vb/showthread.php?t=237737

but this is only for it popping out of 3rd and/or 4th gear so it lkely doesn't address this problem.



.

UnknownJinX

Thanks for the tip. I am still relatively new to driving a stick. So are you suggesting that I should just sequentially upshift then?

See, I almost never tried skipping gears when upshifting in my beater Corolla because, well, it's a POS. I did try to do a 2-4 skip on that car and I heard some nasty grinding. Never tried skipping gears when upshifting on that car again. Downshift-wise, the most common skip is 4-2(from cruising to making a turn, and I rev match), and I never had any issues on both MT cars I have.

So Redline = bad?

Sorry, I must have missed it in this forum. I know Royal Purple MTF will eat up our synchros, but is there a thread about Redline one doing the same thing? Thanks!

I decided to talk to my dealership about it and see what they can do. Booked an appointment next week. I am determined to fix this since I don't really want to deal with double-clutching every time. I will also switch to the Mortorcraft MTF. Again, thanks for the tips, everyone.

Steve Dallas

When choosing a gear, you need to think about where the RPMs will likely naturally fall, when you are ready to put it into gear and let out the clutch. Revving all the way to 9K, then choosing a gear that will be at 3K at your current speed, is not the way to go, unless you are planning to double clutch. Ideally, your RPM will be within 500 of where they should be for the chosen gear, before you start letting out the clutch.

I don't drive like a bat out of hell on the street, so I don't do this very often, but if I were to do a 1st gear pull to 9K, I would at least shift to 3rd, before going to 5th. First gets you to what, 35mph? Then you cruise in 5th? What are you driving on? Residential streets?

I'm much more likely to take 2nd gear to 9k on a freeway on-ramp or something, where I top out at 60mph. Then, the higher gears make more sense. And it's on a freeway rather than a neighborhood.

For my part, most of my gear skipping is limited to skipping 4th, if I'm planning to cruise in 5th, or skipping 5th, if I'm planning to cruise in 6th.

Anyway, spend some quality time learning about rev-matching. It is something you MUST learn to drive a manual transmission correctly. And, it applies to upshifts, as well as downshifts.

I have read a handful of complaints about Redline transmission oils. I have also read tons of glowing reviews. I have never seen any evidence that there is anything wrong with Redline oils. For my part, I have 5 years and 90 track hours on MT-90 in the trans and 75W90 in the diff, with no signs of degradation in either. The oils always come out clean and clear, with very little metal stuck to the drain plugs. It works great for me.

The Motorcraft oils are well-known to be great in Miatas and RX-8s, so they are a fine choice for street cars.

.

UnknownJinX

Thanks for the input!

I start to learn that the RPM will take a while to drop on the RX-8 if I rev it all the way up, so I now take my time when I shift so I don't get a huge jerk and wear my clutch out. I believe at 60 km/h(38 mph), 1st gear is at about 9000 RPM, 2nd gear is at about 5500 RPM, while 3rd gear is at about 3500 RPM.

Are you saying that sequential upshifting is still the best?

I drive my cars pretty hard. I love revving up the Accord V6(would make a VTEC joke here, but that car doesn't have a performance VTEC, so can't really make that joke), and revving up the Corolla was kind of a necessity if I am trying to get on the highway. Of course, I only rev the snot of RX-8 when it's safe(open road, no cars in front of me, dry road) and I wouldn't do it in a residential area, but if it's a good night out, I might redline 3~4 times in a trip.

I am starting to get good at rev-matching on the RX-8, but I still need practice.

As for the MT fluid, yeah, I didn't see anyone saying Redline will destroy synchros. I read on rx8help.com that Royal Purple will have some bad effects on them. I read on some car forums that the Motorcraft gear oil will be a bit thicker when cold, but when it warms up, the shifting feels very good.

Steve Dallas

Yes. I would shift sequentially or start double-clutching. Really, I can't think of a reason to go from 1st to 5th, with an RPM differential of something like 6,000.

If you are feeling jerking in the drivetrain, you are definitely not operating the car optimally, and you could very well be stressing things toward the point of damage.

I don't do many 1st gear pulls. It's not my thing, and the car isn't terribly good at it anyway. So, my shift sequence is typically either 1 - 2 - 3 - 5 or 1 - 2 - 3 - 4 - 6. If I were doing a 1st gear pull, I would probably go 1 - 3 - 5, assuming 5th is the target top gear.

The power band in this car realistically starts at 6,000 RPM, so you want to use the available gears to keep it between 6 and 9,000, and you want to do it in a way that is kind to the synchros and everything else. Show your car some mechanical empathy.

I save all of my spirited driving for the track, and that presents a whole different set of considerations.

.

UnknownJinX

I wasn't intending to shift into 5th from 1st. I was going for 3rd, but accidentally moved the **** to far. I guess I will just stick to the basics for now, just sequential up shift.

I'd say 90% of the time I can shift very smoothly on the car, but there are those time where I had to do things quickly, so I would panick a bit. I will have to keep practicing.

I really like 1st gear pulls if conditions allow. I know that this isn't something RX-8 is particularly good at, but I recall that the RX-8 gets about the same 0-60 time as my old Accord V6, which is still fairly impressive.

When I get better I will definitely go to the tracks to practice.

micvite

so... my 5th gear now grinds at high rpm (say redline in2nd shift to 5th or downshift 6-5 at say 5-6k rpm (rev match to 7.5 for 5th) other than that working fine... my vin is below ALL of the updates... is it worth getting a used tranny from an s2 or should I rebuild mine? And what sort of cost can I expect from going either route if you have any experience. My other question is, say I stop driving like an ******* when using 5th gear am I going to be safe for a while? Here is my vin... sadly JM1FE174690401317

I sadly ground I think 3rd and 5th once or twice prior to this (released the clutch before it was fully in) keeping that in mind what would you recommend?

P.S. thanks for the help with my issues before, I ended up finding the ssv vacuum line pinched inside the intake (4different spots, they basically ran the thing inside the intake when they rebuilt the engine... so I'm waiting on a new one and seeing if that fixes everything!)

UnknownJinX

Repairing is pretty expensive. The only reason I repaired mine is that I couldn't find any used S2 transmission near me, otherwise, I would have gone that route. Used gearboxes can be had for under or around $1k while transmission repair could easily cost double or triple. If money is tight and you don't use 5th, you will be okay for the time being.

If you grind gears very occasionally, it's nothing to worry about, though it may be an indication your trans fluid needs to be changed. My old XT-M5-QS fluid made my 2nd grind at times randomly(revs weren't even that high when they happened) after a year of use. The fluid was dark coffee black when I changed it with my friend and he even noted it smelt burnt to him. I put in some Motul Gear 300 and it works fine now. No more grinding.

micvite

sigh... is it really that much? I figured I just needed to replace the syncros (only had 5-10 grinds since I got the car, some my fault and some because well it now grinds) none of the other gears grind from what I can tell, just 5th at high rpms. Can I still use 5th during normal driving without destroying my whole tranny? I can do the work myself I just need to find a way to pull the trans out (no tools or much space or flat ground for jacks) I guess I'll get the fluid changed for now (should I get the diff fluid done too? Car feels a bit chattery at slow sharp turns) and is motul 300 the way to go for trans fluid?

UnknownJinX

Looked at my invoice from the logbook. Parts were CAN$750. Depending on the situation your gears may need to be replaced as well, which in my case, yes, the gear was replaced. They even gave me the old broken parts and they are sitting in a closet somewhere.

Rest is labour, so if you can do the work yourself I guess yeah, it's a lot cheaper. I heard it's a pretty intensive process, though. That's probably why the labour costs so much. Maybe try an independent shop? I used the dealer, you don't have to though.

You can still use your 5th if you double-clutch or just make sure it doesn't grind.

You can do your diff fluid if you wish, I did it when I changed the trans fluid but it was super clean when I changed it, so I personally will have much longer intervals for the diff.

As for gear oil, lots of choices. About the only one to really avoid is Royal Purple as words have it that it damages your synchros. I use Motul Gear 300 by recommendation from a pretty knowledgeable Focus owner(you'd think he'd recommend the XT-M5-QS. Nope.) and some searching shows it's a good fluid so I gave it a try. So far, I am pretty happy with it. The Focus guy told me it may not last that long before degrading, but if anything, they are a lot cheaper than XT-M5-QS at where I live. Motul makes a lot of oil for motorcycle use, so it might actually be more suitable for our cars - not a lot of torque, but high revs.

NotAPreppie

I've got an S2 gearbox in pieces on my workbench in my garage... Just the synchros are in the range of $100-$150 via Mazda Motorsports Development (probably more at retail prices) and you'll want to do all of them if you're doing one.