5th gear synchro
 

Got into the tranny and the 5th gear synchro out with no problem. Thought someone might be interested in what a bad one looks like. It was broken in two places but only one break was all the way through so the piece didn't drop into the tranny. When I got it out I pulled on it a liitle bit and it broke in half. The moral being if you hear it grinding into 5th DON'T force it. If the ring broke in half I would have had a lot more damage.

Could you post a picture of your Trans. I am in the process of changing out the clutch and would like to do the 5th gear synchro while in the vicinity.

Thanx

See if these help. #1

https://www.rx7club.com/attachment.p...1&d=1192968520

#2

https://www.rx7club.com/attachment.p...1&d=1192968463

#3

https://www.rx7club.com/attachment.p...1&d=1192968542

https://www.rx7club.com/attachment.p...1&d=1192968577#3

Not sure why that last one posted twice?!

how about a shot of your 5th/ reverse hub set? i bet the teeth are shot on that too

mike

I'll have to look closer but do you mean the ones that are out of the tranny in picture #2 or the ones still on the main shaft?

Jim

its still on the mainshaft, its the thing the synchro fits in

mike

Thanks for the pics and info!


This thread is a keeper.

hey.......

When I first got my 7 the 5th gear synchro was busted also. If you don't mind me asking, how did it happen? What did you do?

Regards, Matt

Missed the 2-3 shift at the strip in Epping NH and hit 5th but it didn't go in. It only took one time and it wouldn't go in to 5th again. I updated the shift select spindle with the synchro repair. The new version is supposed to have a stiifer spring.

Thanks j9fd3s I'm definitely going to go into the tranny further with that advice.

Jim

Yeah my 5th is shot too. Gotta double clutch that shit to avoid grinding. It sux.

Excellent pics. Thanks.

I get grinding when i shift from 3->5. Is this a 5th gear synchro problem?

how difficult was the whole task of replacing it? i think mine needs replacing and i want to do it myself.

You might want to consider changing your 5th gear ratio while you're in there to make it not suck so hard.

I'm doing mine right now and I'm putting in a .806:1 rather than the stock .719:1

This will give me a more useful 5th.

Brian

yeah mine is shot too I think. For me to get into 5th though I just wait a sec. or two and then shift 4->5 and it doesn't grind then. So maybe it's not hurt too bad.

Wargasm,
Is that a stock gear from some other tranny or did you have one made?

shmaLbus,
Not difficult and really no special tools needed that you can't make yourself to get at the synchro ring.


Jim

Is this problem with all Fds of just specific(sp?) years. Not to sound stupid, but how would you double clutch. are you taking about like the big rigs, where you got to press the clutch twice, or is this some racing terminology

Very helpful pics! I have to replace my 5th gear sync as well. Ill have to save those.

FYI, there should be a 4 after 3, but before 5. That could explain the grinding :)

Double clutch in the way he sued it is where he presses the clutch in once puts it in nuetral pushes the clutch in again and then puts it into 5th. Maybe not in this exact way but that's the basics and it happens faster than it sounds. ;) :p: :D

yes, the taller 5th gear of the fd means that the synchro has to slow down the gear even faster (than say a t2), conbine this with a misshift, and you exceed the strength of the synchro. putting a lower (or lighter) 5th gear, would improve the "problem" but the broken 5th is common to every 5 speed r box from 1970 to 2002.

mike

wargasm, Any particulars on that 5th gear you mentioned?

What is the stock 5th gear synchro made from?
Is it possible to buy a stronger one?

Re: 5th gear synchro
 

jkekeisen

How did you get the nut off the countershaft?

Sorry didn't see this before.

This is a 5th from another model of RX-7 in Japan. PM me if you want more info.

Brian

Where in MA are you? Wanna help me do mine sometime? :D

Once the synchro is fixed consider getting a B&M short shiter. They are cheap(~$150) and have an extra lateral spring that centers the shifter making it damn near impossible to hit 5th when doing a 2-3 shift (the common cause of sychro failure). In the 2 years (40k miles) I've had the B&M in I can honetly say I've never missed a shift.

Jon
'93 SSM base
working 5th gear synchro since '01

Re: Re: 5th gear synchro
 

There are two ways I know of to get the nut off. The problem is that the shaft will want to turn the transmission shafts rather than back the nut off.

option 1 - put the transmission in 1st gear and hold the input shaft in a vise (using wood or cloth to avoid damaging it). Now that it's secured from moving, take off nut.

option 2 - remove one or more of the roll pins that are set in the 1/2 or 3/4 or 5/R shift select spindles. Now that you can move the shift selectors independently of the shift rods, you can put the transmission into a double engaged condition. For example, select 1st gear and 3rd gear at the same time. This will lock the two shafts of the transmission so they can't turn. Now remove the nut.

Brian

Coming from Wargasm...that just sounds bad.
Ok real question...Has anyone heard of any custom ratio sets? Just curious because my friend has an 86 and there are several custom gear sets for his tranny.

There are 3 5th gear ratios I know of for the FD:

0.719 : 1 - stock
0.762 : 1 - From Turbo II
0.806 : 1 - From RX-7 Type R Bathurst model in Japan (I have this one in my car now)

There are also COMPLETE gearsets you can get such as the HKS transmission or the Guru Racing transmission, but those are MUCH more expensive and a LOT more work to install.

Brian

how much did the new 5th gear syncro cost you? did you buy it from the dealership?

another way to remove the countershaft nut, use an impact wrench.

I think the question was how to hold the shaft still, not how to put torque on the nut.

Dave

By using the impact wrech, you do not have to hold the shaft still.

Btw, the TurboII 5th gear has 2 ratios depending on the year. 89-91' is slightly taller and the 87-88' is lower.

5th synchronizer gear part # W501 17 725c was what I used I think and it was around 20 dollars from Ray Crowe/Malloy Mazda. Ray is the only Mazda person I deal with and he always makes me happy :) Give him a jingle at 888 533 3400 and ask for Ray.

Brian

thank you this thread was very helpful

My t2 'box does this also. I have to double clutch into fifth. Should i be worried about the syncro letting go and going throughthe gearbox?

So I'm in the reassembly stage of this, how do you press the bearing back on? The one you use the extended pullers to get off?

^ Problem solved, found a big enough pipe in the basement and hammered it on.