Hi. I'm grinding 2nd if shift over 5K, and for what have read have a bad synchro. My question is if don't shift 2nd over 5K, I am damaging anything else in the trans? I'm planning a trans fluid change to alleviate thei. Any recommendation? Mine is a 2007 wit 42K miles in the odo. Thanks.

 

if it doesn't grind, then it is not doing damage.

in addition to the fluid change, you might want to check the clutch freeplay, click on freeplay adjustment, takes 3 seconds if its in spec, about 90 if you actually have to adjust something.

and then shift slower

EDIT: link would help i'm sure http://foxed.ca/rx7manual/2003mazdar...041030W01.html

 

Thank you. Excuse my late reply.

 

Hi everybody. I'm reopening this short thread only to let you know that my "bad grinding 2nd shift" has gone like magic. Is this posible? 4 years with the grinding 2nd gear shift if shifting over 5K and the only thing I did was under 5k shiting to 2nd. Today I notice the problem resolve by itself. I can go all the way to 9K and shift to 2nd with no problems. How is this? Any one with the same situation? Thanks.

 

I'm having the same problems when upshifting to 2nd at 4000 or more rpm, doesn't happen during downshifts. Changed to royal purp gear oil, shifts smoother but still grinds at high rpms. Only changed fluid 60 miles ago. How long until I see a real difference? How many hours or days to replace synchros?

 

2nd gear grinds when upshifting at 4000 RPM or more. Doesn't grind while downshifting, just changed gear oil to Royal Purple, shifts smooth ER but still grinds. Could it be synchros? How long does it take to replace Syncro? A few hours or a day or two days?

 

Don't use Royal Purple. You want a GL4 fluid. GL5 ruins synchros. It's possible the synchro is damaged beyond what fluid alone can fix.

Rather than replacing a synchro, I would just find a known good transmission.

 

Let's just say that I had mine repaired(5th gear synchro), and I prefer not openly discussing it. No rebuilt ones are available around me and the only used ones are also stupidly expensive.

Go for a good rebuilt one instead is a much better decision if you can source one. Shouldn't be hard in the US.

 

My fourth gear grinds sometimes at high rpms. Usually if I let it pause before the gear it sometimes won't grind or if I double clutch it, it doesn't grind at all.


When I autoX, getting back into 1st gear can be a bitch at high rpms.

 

You're not supposed to need 1st. 1st on these cars (all cars?) is really just a 'get rolling' gear. Shifting into it at speed is just abuse :/

 

A lot of people use first gear, rx7's corvette's, GT3's, Miata's all shift back into first on some of the corners.


Does the rx8 have some sort of locking feature to lock us out of 1st gear when moving? Another thing I could do is run smaller diameter tires.....

 

No locking feature, just the speed differential between mating gears is waaay too high for the synchros to absorb properly. You have to revmatch it perfectly.

How fast would you say these corners are? Because I somehow doubt that a GT3 or Corvette who knows what he's doing is giving up a downshift and subsequent upshift back to 2nd to pull through a corner. He's got plenty of grunt to do the whole thing in 2nd with less drama.

I did it once, I didn't like the sounds it made, and it turned out to be the slow way to do that corner.

 

My old Corolla would grind if I try to downshift into first gear at speed. Some cheap econoboxes are said to not have synchros in first gear. That, or the synchro was shot.

I don't think downshifting into 1st is really necessary unless you need that much straight line acceleration, which our cars are not really great at anyways. I don't downshift into 1st unless I am below 16 kph/10 mph. You'd have to be pretty good at rev matching to pull it off.

 

A properly operating RX8 trans downshifts into 1st gear no problem

 

I rev match and downshift into 1st, at speed, every day. It doesn't need to be absolutely perfect by any means. You just can't force it into gear. Even in my first car with the 1st and 2nd gear synchros almost completely shot there were no issues with this.

Something tells me people aren't downshifting properly.

 

here is the corvette using 1st gear in a lot of the section. keep in mind that we are at 6K+ ft above sea level and when the revs drop to 4K rpms you need to go to first. We are talking about an rx8 with not much WHP. If an rx8 has 185WHP at sea level that power up here is only 145WHP.

 

These guys compete at SCCA nationals, at least some of them do. some are instructors and they use first gear. Perhaps my gearbox is trashed. I will definitely trash it around some more but the 2011 gearbox is the most robust of them all? just use a different mating plug at one spot?

 

It's been 3 weeks since I started using Royal Purple Gear Oil, I have definitely noticed significant improvement. Smoother shifting and my 1-2 only grinds above 4000( before change, grinded above 3400rpm) , so I won't need a synchro rebuild until I'm ready to take it to the track, and that won't be for a while. So my throw out bearing blew up and slave failed at some time a week ago. Replaced bearing and both master and slave and now 1-2 only grinds above 5000rpm.

 

That's cool but you're going to want to get that royal purple out of there. It's a GL5 oil, these cars take GL4 and GL5 eats synchros. Use RedLine MT90. Usually rebuilding these transmissions is more expensive than just finding a used known good one.

Check that your clutch pedal is properly adjusted. It could be not disengaging the clutch all the way.

 

Readjusted clutch pedal when I changed throwout bearing. Will the Royal Purple be safe for a few months? I'd hate to have to change it right away, that stuff was pretty expensive. But a rebuild is much more expensive so idk.

 

I would say use something else ASAP. Either Redline MT90 or Ford Motorcraft MTF is good.

 

It's a chemical reaction so there is no safe period. The shorter the exposure, the better unless you're planning to junk the trans anyway. No fluid is going to fully fix damaged synchros. So, you have some decisions to make there.

 

Redline is expensive, is any cheap GL4 better than the Purple. On a side note my tranny just stopped grinding all together earlier. Pretty stoked about that.
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Everytime it grinds is the greater the internal damage you're causing and the shorter the synchro life will be, if it's not too late already ...

 

Ordering MT90 today. Can I put the Royal Purple in the rear diff? It only has 200( maybe less) miles in the tranny. And tranny was flushed before filled, so there shouldn't be much if any contaminants in the fluid. I know I sound SUPER CHEAP, but I'm on a very very tight budget