ViperBart

iTrader: (3)

I need a gear between 4th and 5th in my FC. It starting to get notchy too when shifting normally. I have to rev match to get any kind of smooth operation. Sometimes I think it shifts smoother not using the clutch.

How much better would the T2 tranny be?

azdk

I'm not a tranny expert or anything but i found out,when i post **** thats wrong,people seem to respond a lot quicker haha.

So,my guess would be syncros are going out????And the t2 is stronger,so if you can get a good priced one go for it.


Now on with the flaming on me and helping you LOL

Icemark

when was the gear lube last changed and what was used?

SCCAITS

iTrader: (3)

Put in a .756 5th gear only found in the GTUs.

1986 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .711
87-88 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .697
89-92 Non-Turbo w/o LSD 3.475 2.002 1.366 1.00 .697
89-92 Non-Turbo with LSD 3.475 2.002 1.366 1.00 .756

Better yet, go with a Miata gearset

Miata 3.13 1.833 1.303 1.00 .840

pfsantos

iTrader: (1)

You can get the 4.5 gear on special at Autozone - part number 5105. It goes between the 4-5 gear on the countershaft. Easiest way to get a 6-speed.





Seriously, I'd change to synthetic fluid, just to minimize further damage, but it may be too late. Your synchros may be going, that is, if all the other gear changes seem fine. Is the 4-5 change rough even when you do it slowly/smoothly?

ViperBart

iTrader: (3)

Isn't that the truth!

2 years ago, about 60000kms with the recommended grade in the manual... can't remember exactly

Best danm info anyone could have replied. (period)

I am guessing your big on sarcasm????

Sorry for the confusion...
1: I think my fifth gear is too long
2: I think my syncros are starting to wear out. I get a rough gear change in third mostly.



And now I'm thinking,
1: Are there any differences between the S4 and S5 T2 trans?
2: Can I switch only the 5th gear from the miata or do I have to change the whole set?
3: Should I rebuild what I have? I don't plan on getting a turbo, but I want to rebuild in the next year with a street port, S5 uim, PowerFC Commander and my current header & exhaust. So would the N/A tranny hold up good with mods like that?

ericgrau

iTrader: (1)

The RX-8 has an extra gear between 4th and 5th. Is this why? I'm not saying it'd fit in an FC though.

After 60,000km I'd change the gear lube regardless. If you get Royal Purple (Synchromax, many sources) or Neo (from mazdatrix.com) it'll be a lot easier to shift too.

ViperBart

iTrader: (3)

I would put synthetics in it if i want to rebuild it... but right now I don't know if I want to rebuild or swap it for the T2 trans.

Sideways7

iTrader: (7)

Be careful, I just got chewed out for saying that yesterday.....

Also, there is more to using a turbo tranny than just putting it in. You need to have a turbo flywheel, turbo clutch/pp assembly, and either a custom driveshaft to mate to your NA diff or a turbo driveshaft and diff.

Another great fluid is Redline MT-90. I have it in mine and love it.

zmannz

iTrader: (1)

Hey, what better time to get used to double clutching? At least you still have a first gear synchro. I have a friend with a bmw 2002 that has NO synchros (claims it is a racing tranny that was built as such?). Interesting drive. As for your problem, why not look into having your stock tranny, or a new one with better ratios rebuilt and/or upgraded? Don't know whats out there for the fc in this division, but a nicer set of synchros would feel great and do a lot to improve reliability.

pfsantos

iTrader: (1)

I never shift too early into 5th because it provides little acceleration. Maybe you're just shifting a bit early? No offense, but it just seems like the easiest solution.

Craiger

iTrader: (1)

The RX8 MT has an extra gear between 3-4, the AT appears to add and overdrive above 5th. The gear ratio's can be found on mazda's website.

Talk to anyone with an Eagle Talon and they'll tell you how much of a difference synthetic gear lube will do. If it's not shifting well, spend the $30 on good lube before you spend hundreds on rebuilding the tranny.

The T2 tranny is a lot stronger but it will be a fair bit of work to swap in. As stated above, it is not a direct drop in and you will have to change a number of other parts to make it work. If I were going to do that swap i'd change the whole rear end all at the same time rather then buying or making custom parts to mate the turbo trans to the N/A rear end.

5th gear is a highway cruising gear for the most part. It's goal is to keep engine rev's fairly low at highway speed to help with fuel economy, without bring so big that the engine bog's down when it comes to the smallist hill. So basically, your not going to get much accelleration out of 5th gear since these engines have a relitively high RPM powerband.

These cars get into highway speeds by the end of 2nd gear. So how fast would you be going if you were actually in the powerband in 5th?? I've never taken my car to redline in 4th (except I guess it would have been there on the dyno) but i'm guessing your around at least 120mph at that shift. The point is if you are looking for good acceleration at highways speed shift down to 3rd.

If you find that the car is completly boging in 5th, I would suspect somthing is up with the engine. Is your compression good? Are the 5th/6th ports working properly? When is the last time the engine was tuned up? I'd check this stuff before you start messing with changing gear ratio's. That's just my .02

Icemark

If you can't remember... it is due.

Try using a good synthetic like Redline MT-90... it helps fix dragging and clashing issues as you have described before ripping apart a tranny and trying to change gears.

Black91n/a

That and any other claim that it "adds a gear between X and X" is completely false. ALL the gear ratios are different. 1st is a little shorter, and 6th is shorter compared to the FC 5th's. So it has about the same spread, but it has another gear in there so the gears are spaced closer together for less rpm drop on shifts.

ViperBart

iTrader: (3)

And after reading some more reply's I'm still wondering...

1: Are there any differences between the S4 and S5 T2 trans?
2: Can I switch only the 5th gear from the miata or do I have to change the whole set?
3: Should I rebuild what I have? I don't plan on getting a turbo, but I want to rebuild in the next year with a street port, S5 uim, PowerFC Commander and my current header & exhaust. So would thestock N/A tranny and clutch hold up good with mods like that?

P.S.
I know the benefits of synthetics...
I know whats invoved in the T2 tranny swap...
I don't really want to change the diff axles etc, that would require too much time and money in the shop...
Don't worry about shifting too early I see 8K very often.... 4th to 5th is at 130mhp when I redline it.... I want a shorter 5th to gain a little acceleration cuz I dont have any in fith at all... dont ask why I try to go these speeds I know its dangerous and stupid blah blah blah....

I was talking about the oil weight... not the service interval.

Sorry if I sound a bit rash in this one... somethinmes its hard to get answers.
Thanks for all your posts.

SCCAITS

iTrader: (3)

1. Yes - From Mazdatrix....

86-88 RX7 Turbo 3.483 2.015 1.391 1.00 .762
89-95 RX7 Turbo 3.483 2.015 1.391 1.00 .719

2. Whole set. Put all the Miata gears in or just put the .756 5th Gear in from the 2nd Gen
http://www.mazdatrix.com/faq/miatainputshaft.htm

3. Yes. Stock N/A can more than handle your proposed mods. Put the Miata gears and consider changing your R&P. Not sure on your usage of the vehicle, but there is the 4.30, 4.88 and 5.12 R&P available. Only the 4.30 is OEM, the other 2 are custom and 4.30 is all you'd want for street use anyways. The 4.88 and 5.12 if you are lucky enough to find them go for about $2k+ for the entire diff.

ViperBart

iTrader: (3)

Cool
So this is what I will do...

Rebuild my trans with .756, install slightly higher performance street clutch and pressure plate, new pilot bearing, new ?throughout? bearing, install new braided clutch lines. Am I missing anything?

I will keep my current 4:1 lsd for now untill i gather enough $ to get the 4:3 and also redo all the rear suspension while I'm there.

SCCAITS

iTrader: (3)

Yes. Where is the lightweight flywheel?

"Throw out" aka release bearing is the term you were looking for. There is only one SS clutch line, goes from the hard line to slave cylinder, less than $20 at Mazdatrix.

ViperBart

iTrader: (3)

Yeahhh... thats the word I was looking for! haha
That's what I meant for the clutch line, I was thinking about the brakes lines at the same time hehehe.
and the lightweight flywheel will come with the rebuild... ahh the heck with it, i'll change that too.

Black91n/a

I know that you can install RX-7 5th gears into the Miata case, so it's safe to assume that you can do it the other way around. Be aware that it won't give you the same exact ratios though, as you're mixing and matching with different tooth counts.

ViperBart

iTrader: (3)

I will have to check out the FSM for the 7 and the Miata, dust off my old tech books and break out the calculator for this one.

I'll see what I can dig out.
Thanks.

ericgrau

iTrader: (1)

Try the synthetic oil first, as mentioned. It may remove your problem or delay the need to do tranny work. Then if that fails get the gears. Note that if you lower your 5th gear then 5th gear acceleration will improve but your gas mileage will suffer a little.

Tangent: see attached graph
If you look at the purple and blue lines it seems like none of the gears match up between the FC and RX-8 trannies. But notice how the RX-8 line looks like a squashed version of the FC line. Change the final drive ratio to stretch it out (yellow line) and it matches up almost perfectly; except there's an extra gear between 4th and 5th. The RX-8 is just geared lower, that's all. This is all just a tangent, though, since neither the RX-8 tranny nor anything inside it will fit in your car.

For a stock FC, 6500 rpm in 4th is at a hair under 120mph.

ViperBart

iTrader: (3)

I live in Canada.
I have no choice to wait for summer for the tranny if I want to keep my fingers attached to my palm. HAHAHA

Black91n/a

Not exactly. Yes it's not a bolt in, but it'll bolt up to the engine, and you can use the TII flywheel and pressure plate. There's still lots of stuff that'll need to be custom though, but to say that it won't fit is a big stretch.

SCCAITS

iTrader: (3)

Anyone able to confirm putting the Miata gears 1st-4th in the RX-7 case and using the RX-7 5th gear of your choice? The Miata 5th is a little too low at .84 for me, I'd want the .756 RX-7 gear. I know about the input shaft modification on the Mazdatrix site.