Pretty sure my trans is done, rebuild and 6-speed questions inside!
#1
Senior Member
Thread Starter
Join Date: Apr 2011
Location: Las Cruces, NM
Posts: 590
Total Cats: 114
Pretty sure my trans is done, rebuild and 6-speed questions inside!
Back story: Blew my motor in January, picked up a low mileage SM shortblock and tossed on a complete '99 head minus TB, same transmission. Put a few miles on it around town over the past week but nothing substantial due to how ridiculously loud and smelly the car is.
Fast forward to yesterday (5/28) and after a ~40 minute incident free track session, followed by ~30 minutes of cool down, during my next outing the car sounded like the starter was hung up with the car in gear with the clutch out. It drove fine but it was making a terrible noise so I pulled into the pit to remove the starter with the plan to just push-start it the rest of the day... no dice. When we finally went to push-start it in reverse with the clutch in it made the same loud metallic grinding noise so I called it a day.
Then when we were pushing the car onto the trailer in neutral, obviously, it made the same noise... So it just progressively got weirder, first it was when it was engaged in gear, then it was without being engaged in gear to whenever mobile...?
I have yet to remove the trans because I'm a lazy slob but I guess I'm looking for worst-case scenario info:
1. Rebuilding a 5 speed, how much does it cost and would I only purchase OEM parts or...?
2. Swapping to a 6-speed, worth it for my current low WHP NA setup?
3. I don't really plan on ever making more than 220WHP with this chassis, should I be considering a 6-speed at all?
Fast forward to yesterday (5/28) and after a ~40 minute incident free track session, followed by ~30 minutes of cool down, during my next outing the car sounded like the starter was hung up with the car in gear with the clutch out. It drove fine but it was making a terrible noise so I pulled into the pit to remove the starter with the plan to just push-start it the rest of the day... no dice. When we finally went to push-start it in reverse with the clutch in it made the same loud metallic grinding noise so I called it a day.
Then when we were pushing the car onto the trailer in neutral, obviously, it made the same noise... So it just progressively got weirder, first it was when it was engaged in gear, then it was without being engaged in gear to whenever mobile...?
I have yet to remove the trans because I'm a lazy slob but I guess I'm looking for worst-case scenario info:
1. Rebuilding a 5 speed, how much does it cost and would I only purchase OEM parts or...?
2. Swapping to a 6-speed, worth it for my current low WHP NA setup?
3. I don't really plan on ever making more than 220WHP with this chassis, should I be considering a 6-speed at all?
#3
Senior Member
Thread Starter
Join Date: Apr 2011
Location: Las Cruces, NM
Posts: 590
Total Cats: 114
I don't really live in an area where Miata parts are plentiful and while I know 1.8 trannies can be had for relatively cheap, I don't mind spending the money on a rebuild, depending on how reasonable it would be, to know I have a properly functioning transmission that won't give me anymore headaches.
I'm not inclined to go to a junkyard and grab one that's in "unknown" condition just because it's cheap. I'd rather have the piece of mind that if I'm at an event I'm not relying on used parts of unknown origin to keep together and not ruin a very costly weekend of lapping.
If this didn't happen yesterday then I'd be trailering the car to a 2-day NASA weekend at Inde Motorsports Ranch next weekend and if the tranny went on me there I'd be out almost $500 in gas, lodging and entry fees... That's not alright with me. This is a dedicated track car that I can't afford to band-aid.
#6
Former Vendor
iTrader: (31)
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,100
If this didn't happen yesterday then I'd be trailering the car to a 2-day NASA weekend at Inde Motorsports Ranch next weekend and if the tranny went on me there I'd be out almost $500 in gas, lodging and entry fees... That's not alright with me. This is a dedicated track car that I can't afford to band-aid.
FYI, I blew out reverse in a 6-speed a couple of years ago (accidentally tried to shift from 5th to reverse at ~120mph). It cost me $350 in parts (5/R shift fork, reverse gear, reverse synchro, reverse selector ring) and $350 in labor (reverse gear is on page ~90 of the 140 page transmission rebuild FSM). The transmission blew up 6 months later (stripped 4th under steady power). A more intelligent person would have bought another 6-speed and kept the sans-reverse box as a spare.
The 6-speed's ratios are a major improvement over the 5-speed ratios. The 6sp's 3/4 ratios are taller and more tightly spaced than the 5sp's 2/3 ratios, and the 6sp 6th is shorter than the 5sp 5th. The fact that it's stronger is just icing on the cake for N/A cars. You can expect to find 0.5-1.0sec by switching, which is why it's a +3pt mod for NASA TT/PT.
If you have 4.10s, I wouldn't bother switching them. For a naturally aspirated car with a stock (<7500rpm) rev limiter and less than 170whp, I would want 4.30:1 gears.
#7
Senior Member
Thread Starter
Join Date: Apr 2011
Location: Las Cruces, NM
Posts: 590
Total Cats: 114
Then buy two $200 5-speeds, put one in your car, and put the other one in your truck/trailer. You'll spend ~$1000-1200 on the parts and labor necessary to rebuild a 5-speed, and while it will probably have better synchros, it will be no more reliable than a junkyard transmission would be.
FYI, I blew out reverse in a 6-speed a couple of years ago (accidentally tried to shift from 5th to reverse at ~120mph). It cost me $350 in parts (5/R shift fork, reverse gear, reverse synchro, reverse selector ring) and $350 in labor (reverse gear is on page ~90 of the 140 page transmission rebuild FSM). The transmission blew up 6 months later (stripped 4th under steady power). A more intelligent person would have bought another 6-speed and kept the sans-reverse box as a spare.
The 6-speed's ratios are a major improvement over the 5-speed ratios. The 6sp's 3/4 ratios are taller and more tightly spaced than the 5sp's 2/3 ratios, and the 6sp 6th is shorter than the 5sp 5th. The fact that it's stronger is just icing on the cake for N/A cars. You can expect to find 0.5-1.0sec by switching, which is why it's a +3pt mod for NASA TT/PT.
If you have 4.10s, I wouldn't bother switching them. For a naturally aspirated car with a stock (<7500rpm) rev limiter and less than 170whp, I would want 4.30:1 gears.
FYI, I blew out reverse in a 6-speed a couple of years ago (accidentally tried to shift from 5th to reverse at ~120mph). It cost me $350 in parts (5/R shift fork, reverse gear, reverse synchro, reverse selector ring) and $350 in labor (reverse gear is on page ~90 of the 140 page transmission rebuild FSM). The transmission blew up 6 months later (stripped 4th under steady power). A more intelligent person would have bought another 6-speed and kept the sans-reverse box as a spare.
The 6-speed's ratios are a major improvement over the 5-speed ratios. The 6sp's 3/4 ratios are taller and more tightly spaced than the 5sp's 2/3 ratios, and the 6sp 6th is shorter than the 5sp 5th. The fact that it's stronger is just icing on the cake for N/A cars. You can expect to find 0.5-1.0sec by switching, which is why it's a +3pt mod for NASA TT/PT.
If you have 4.10s, I wouldn't bother switching them. For a naturally aspirated car with a stock (<7500rpm) rev limiter and less than 170whp, I would want 4.30:1 gears.
Only thing I'll add is that I wouldn't have to pay labor as my BFF fabricator would have handled it for either next to nothing or exactly nothing but given your cost run-down I doubt an entire 5-speed rebuild would be cheaper than an >$800 used 6-speed.
So it looks like I'm saving for a 6-speed...
#10
It's not a 6speed, it's a 5speed with a dogleg 1st (standing starts would be done in 2nd)
But the shorter 6 means that you need to rev a bit to get some speed out of it.
Our longest straight is nothing compared to yours and I reach 6500 with 5sp and 4.875 with stock power (cage an no top means about 500rpm penalty due to drag).
But the shorter 6 means that you need to rev a bit to get some speed out of it.
Our longest straight is nothing compared to yours and I reach 6500 with 5sp and 4.875 with stock power (cage an no top means about 500rpm penalty due to drag).
#18
Senior Member
Thread Starter
Join Date: Apr 2011
Location: Las Cruces, NM
Posts: 590
Total Cats: 114
Just drained a cup full of smelly fluid from my trans, I'm guessing they require more than that?
I vow to not get so drunk when I'm working on my car from here on out... God it's gonna be so boring.
I vow to not get so drunk when I'm working on my car from here on out... God it's gonna be so boring.
Thread
Thread Starter
Forum
Replies
Last Post
bigmackloud
Miata parts for sale/trade
19
01-08-2021 11:24 AM
Zaphod
MEGAsquirt
47
10-26-2018 11:00 PM