Reinforcing the 6MT transmission
 

Hello fellow Z owners. My car has about 50 000km and 4th gear is starting to show wear signs such as being clunky when shifting and not being smooth.

Is there a way to bullet proof the manual transmission? I don't want to buy another OEM transmission that will fail the same way over time.

It's a street car but I'm hard on it. I like speeding and found out my car was speed limited at 240 kmh in 5th gear. Would there be a way to remove the speed limit at low cost? (The dealership is a relative and probably told the mechanic to put the limiter)

Modifications done so far:
I already have a Stage 2 clutch kit with the lightweight flywheel from Zspeed along with their CSC delete kit. GReddy GT Evolution catback exhaust and Fast Intentions HFCs are on the way. Also have a Mishimoto oil cooler kit. K&N drop-in filters with Mishimoto silicone intake tubes.

Sport and Touring package

Thanks

150mph in 5th sounds about right. I think you hit the RPM limiter, not the speed limiter. Top speed is supposed to be around 165 mph (~265 kph).
I have heard tales of people having their 6 speeds rebuilt with Ford synchro's, making them more durable. A search in the tech part of the forum would reveal more on that. Haven't needed the info, so I haven't researched it. From my limited reading, the rest of the transmission seems to hold up well.


Kirk B.

Nothing really out there in the aftermarket world for our 6MT's. Just get a brand new one from Nissan and don't miss any shifts or abuse it.

No transmission is bullet-proof - if you abuse it, you're gonna break it. The 6MT is pretty stout - some people on this site are FI'ed and running stock 6MTs with no problems. You should be able to find more than one thread on this site about beefing up the 6MT (IIRC, there's not a lot you can do) and how to use the 6MT properly. Personally, I'd get a reputable shop to rebuild the trans; might be able to find some beefier synchros to put in there.

The speed/rev nannies can be adjusted when you get your tune.

LOL, this is true. No issues with 824hp at the wheel. You just have to drive them properly.

There was one member who was redoing the trannies. But he hasn't been on for a few years.

The Z is speed limited to 155 mph. To remove it. You have to use UpRev, or Ecutek tuners.

Zingston does trannies every day?

Sent from my SM-G955U using Tapatalk

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I'm disappointed. :( There's nothing about Jar in the tags. :shakes head:

No I still had about 100 rpm before hitting the rev limiter which was set at 7600 rpm by the dealership. It was speed limited because the speed and rpm wouldn't budge.

Thanks for your imput.

Is it possible the clutch kit was not properly installed or adjusted and that way it would not fully disengage? But thinking of this, it should not affect the transmission but it should affect more the flywheel and shift shaft?

There are no transmission shops nearby as I live in Eastern Canada and pretty far from Montreal.

I think I might be obliged to buy another OEM transmission.

Would the dealership be able to "rebuild" my current transmission by replacing the synchros with OEM?

The stock rev limit is 7,800. You can change that with Uprev or Ecutek. Why would the dealer lower the rev limit? Plus I don't think the dealer has that option with their software.

Are you talking about when the rev light flashes? If you are. You can change that yourself.

My car was rev limited at 7500 rpm when I purchased it. I asked the certified mechanic to raise it to 7600 which he did.

The certified Nissan mechanic said he can change the speed limiter, rev limiter and timing but he did not want to change the timing when I asked him to advance it.

All the modifications were installed by that mechanic.

How did he raise the rev limit? On the dash on the right side, where the gas gauge/water temps lights are?

With the dealership ecu management computer.

It doesn't sound like a clutch problem to me, but I'm no expert.

My guess is that less than perfect shifting skills is the main problem. Or it could be you got a bad synchro from the factory. But, given the reputation of the 6MT, I doubt the stoutness of the transmission is the root problem.

I wouldn't trust any dealership to do any out-of-warranty work. And if I can do the in-warranty work myself, I do. YMMV

I haven't rebuilt a manual transmission in quite a while and they were all much older then the 6MT (eg, Ford Toploader) but it's not a difficult job. The FSM (link in my sig) will have exploded diagrams and may have a rebuild procedure.

Not for nothing but I make a a couple ugga duggas above 700rwhp and at 150 it was time for me to go to 6th gear. I would have more in it in 5th if I did'nt have Nismo FD but for basically a stock untuned Z to be at 150 in 5th it does'nt seem as if the issue is the tranny. Our tranny is at a point now that other swaps are looking at it as an economy option to hold power without building their own OE tranny.

The only way to bullet-proof the transmission is to replace it.

You have 2 obvious choices and some not so obvious.

1. QUAIFE QBE69G with syncro on 6th
2. HOLINGER SG3 if you are not boosted and RD6 if you are

The QBE69G and SG3 will be about the same cost and the RD6 a shed-load more.

Other options is
3. TTI 6-speed sequential from New Zealand

These will not break BUT they are race transmissions and straight cut in lower gears and whine like an entitled millenial who has been separated from his mothers nipple too soon.

These options will cost the equivalent of 4-5 OEM replacement transmissions - apart from the RD6 option which will be USD20K+

Simplest solution is replace the OEM trans

Street car but hits 150 mph
Transmission failing at 30k miles

Does not sound like a hardware or software problem

These transmissions are not worth rebuilding. You toss them out and replace for about $2000.

Changing or removing speed and rev limiters can be done with a tune. Find an UpRev or ECUTEK tuner to tune your car.

I recently replaced my transmission, 2k+labor. Not too bad for a new transmission. Lasted 70k miles and many many miles/hours at the track. I was pushing it pretty hard through the gears when the 5th gear synchro gave out. It's the only weak part of the transmission, you really have to baby it so it won't grind. Even then new one has the same 5th gear issue.

What is the highest speed and rev limit on these cars, especially NA?

Highest speed and rev limit depends on a whole crapload of factors.
Final drive ratio will lower top speed, aero and power. Rev limit will have to figure in upgraded oil pump (which ironically doesn't tolerate much over 8k in oem form. But imho a sensible non race team build wouldn't be looking to go too far past an 8k limit without an Amex Black burning a hole in someone's pocket.

Stock, rev limit is around 7700 rpm. Speed limited to 155 by both ecu and aero.

HEY I'M A MILLENNIAL AND I TAKE OFFENSE TO THIS.
WE AREN'T WHINY AND... Oh.... you've made your point.

:shakes head: