2002 NB Miata BEGI S4 @ 12PSI. 5 Speed. I'm making around 260.

I shifted hard into second gear today just around the corner from my house. I noticed while pulling in I had a rather loud knocking noise. My first thought was rod knock but then I pressed the clutch and it went away.

If the clutch is pressed, no noise. If I put the car in reverse and roll back I can feel the resistance when the knock noise hits. Happens less in first but I'm not sure what the problem is.

Could it be that my throw out bearing has exploded or is out of whack? Or did I break the trans?

 

Anyone have experience? Rebuilding? Whats weak?

 

You'll want to get under the car and make sure you didn't kill a u-joint or the diff first. Once you know those two are ok, probably need to pull the trans to see if you killed the trans or clutch (though from your description I'd say you killed the trans). You're right about the hp level where 5 speeds blow up with regularity.

Once you confirm it's the trans then you can decide whether to go 6 speed and generally not worry about the trans anymore or start shifting nicer and try to keep a 5 speed alive.

 

looks like it was the trans. Broke a couple of teeth off, near the input shaft. Anyone have an exploded view of the transmission? I'd like to replace that gear and use that transmission as a backup. It only has 47k on it and looked great from the inside.



Anyone done the 5 to 6 speed swap? I'm not trying to replace my diff but from what I read, it's a different ratio for the 6 speed. New clutch or can I rock my fairly fresh ACT?

 

I broke the part called the Counter Shaft. (17-301) The third gear from the front of the car on that shaft, has two teeth missing. Unfortunately, its all one piece and 400 something from the dealer. I found it for 200 online, but I'm going to just pick up a used transmission for a couple hundred. I just figured I'd post this up for reference.

 

5speeds are weak.
Your options are:
1) buy a 6 speed
2) never shift fast or hard
3) keep replacing blown 5 speeds


Its interesting you stripped the shaft though. Usually its just the gear itself

 

I was looking into the 6 speed. Seems like it's a bit of a bigger commitment than just replacing the transmission. Something about the diff ratio from a 5 speed is not a good combo? Have you done the swap?

I also broke 27-158 on this exploded view:

 

You can use this nifty calculator to decide if the ratios are not good:

http://www.flyinmiata.com/tech/gearing.php

 

Awesome resource.

To me it's just not worth it. The trans is well over 3 times the cost (from what I've found) and I have an LSD with a 4.30 ratio, that I'm not trying to replace. That would take my first gear from 36 to 30 and my second from 60 to 50. Doesn't sound fun and the last thing I need is the extra revs on the freeway.

 

1st gear is for pulling the car on the trailer, 2nd gear is for cruising the pits, 3-6th is for being a hero. I think the ratios are pretty awesome with the 3.63, awesome enough that I just bought another 6-speed to go in my daily driver.

 

Right, but I don't have the 3.63 :(

What are you finding the 6 speeds cost? I found a 5 speed for 200 bones with 70k on it.

Anyone cryo treat their miata trans?

 

I find them all the time and the most I've paid is $600, the least is $250. We have threads on this but I'll tell you that cryo and micropolishing are a waste of cash. A few people have done it, including a local, and the local trans lasted 2 sessions at 290whp.

 

Alright. I'll toss on another 5 speed. I'll work towards the 6 speed and a diff over the winter.

 

Its expensive and the ratios suck without a proper fd (for a street car at least IMO) but its damn strong and wont take a crap on you after the 1st hard shift

 

I spend a good amount of time playing with the local guys from light to light. Usually a 1-2 gear pull and we shut it down. I'm running the gt2860 and spool relatively early for that sized turbo... Considering the 6 speed with my ratios.. How much will this really slow me down?

 

Always be in 1 higher gear. So from a stoplight rollout just go from 2nd.

 

Hmm. Can you get a decent launch from 2nd? Or does it still make sense to start with first from a stop? I wish someone locally had the same setup that I could just go drive. Also- is your speedo off?

 

I had the 4.10 torsen with mine and the speed was off by something like 5mph. Not bad at all. This was with 205/45/16 wheels IIRC.
I never launched my car from 2nd, just did a roll out (ie: shift from 1st to 2nd immediately then get on it), but I've seen others launch from 2nd no problem.

 

Only because you used the wrong speedo gear. If you keep the speedo gear from your 5-speed (it fits right into the 6-speed) the speedo will not change at all.

Buying another 5-speed is a waste of money. This isn't a fluke, you broke it because you make too much power for it, you'll just break the next one too, and if you want to never deal with it again you should probably just buy a 6-speed.

Sell your 4.3 Torsen to a Spec Miata guy and buy a 3.9 Torsen. Or spend a bunch of cash on the 3.636 if you think it will be better. If you can do the tranny swap, you can do the diff swap.

I run a 3.909 diff.

 

3.6 is hands down the best for street IMO