Question for 6 speed owners

Hack · Nov 8, 2004

For those of you with 6 speeds.. have you ever missed a downshift?

I recently heard that the gears are a little closer together on 6 speeds, making it more likely that the wrong one might be chosen. The guy who published this information actually downshifted to the wrong gear during a race at over 100 mph. His motor revved to 15,000.. for a short time. So he runs 5 speeds to avoid trashing another motor.

I mentioned this at work to a coworker who has a 6 speed in a newer V8 Camaro, and he said he has done the same thing.. although he didn't break anything.

When I put the manual trans in my car, I want to drive it hard. I want to be able to downshift when necessary in autox events, etc.

Any feedback?

gp001 · Nov 8, 2004

Hack said:
For those of you with 6 speeds.. have you ever missed a downshift?

I recently heard that the gears are a little closer together on 6 speeds, making it more likely that the wrong one might be chosen. The guy who published this information actually downshifted to the wrong gear during a race at over 100 mph. His motor revved to 15,000.. for a short time. So he runs 5 speeds to avoid trashing another motor.

I mentioned this at work to a coworker who has a 6 speed in a newer V8 Camaro, and he said he has done the same thing.. although he didn't break anything.

When I put the manual trans in my car, I want to drive it hard. I want to be able to downshift when necessary in autox events, etc.

Any feedback?

It is not that the gears are physically closer so much that you would put the shifter into the wrong location, it is that the ratios are closer so if you do happen to put the shifter into the wrong gear the change in RPM is very noticeable. T-56 6 speeds don't have as much of this problem as say a Richmond 6 speed because the T-56 ratios are not as close as the Richmond. If you compare the physical shifters of a T-5, 3650, T-56 I would imagine they are very similar.

Max Power · Nov 8, 2004

I've always thought two overdrive gears was one too many.

Fostang · Nov 8, 2004

That's about the stupidist reason to run a 5 speed instead of a 6 speed.

Hasn't he heard of a rev limiter.

Hack · Nov 8, 2004

Fostang said:
That's about the stupidist reason to run a 5 speed instead of a 6 speed.

Hasn't he heard of a rev limiter.

How is a rev limiter going to stop your motor from turning 15,000 rpms when you downshift into second at 100 mph? You could have the ignition and the gas completely off, and the torque from the rear tires would still force the engine to turn.

Either that, or since you're probably downshifting in a turn - already at the limit of traction - if you break the rear tires loose you could go splat. Lunching the motor might be a better outcome.

Yeah, I guess maybe it's a dumb reason to go with a 5 speed. However, I see safety as one of my key concerns for this car, with keeping the cost down as a close second. If I was just going to drive on the street, I wouldn't worry about this at all. However, I plan on racing some amount and I believe that makes all the difference in the world.

Thanks for the replies. Sounds like none of you have done this. Maybe I worry too much.

nosaj122081 · Nov 8, 2004

Fostang said:
That's about the stupidist reason to run a 5 speed instead of a 6 speed.

Hasn't he heard of a rev limiter.

Rev limiter won't limit the rev's if the motor's FORCED to spin that fast by a wrong shift... Only limits it via the throttle.

6Stang7 · Nov 8, 2004

I call It would be hard as hell to get it into gear if it would have spun his motor up to 15K when he let off the clutch.

nosaj122081 · Nov 8, 2004

6Stang7 said:
I call It would be hard as hell to get it into gear if it would have spun his motor up to 15K when he let off the clutch.

No it wouldn't... Assuming the gears are all synchronized. Ever try to put a 5 speed in 2nd doing 70? No big deal, and would easily hit 15000 RPM, at least before parts came flying through the hood.

gp001 · Nov 8, 2004

You wouldn't miss a shift any more or less based on the number of gears the trans has. It all has to do with shifter type, shifter position, and driver. If you miss a shift, or downshift to wrong gear, in a 6 or 5 speed it would likely have the same result. In fact, the first through fourth gear ratios in the T-56, 3550/TKO, and T-5 are relatively identical, so a missed shift with any of these trans would have similar results.

6Stang7 · Nov 8, 2004

nosaj122081 said:
No it wouldn't... Assuming the gears are all synchronized. Ever try to put a 5 speed in 2nd doing 70? No big deal, and would easily hit 15000 RPM, at least before parts came flying through the hood.

Yes I have, and it's hard to get it into gear. Shifts perfectly though.

reenmachine · Nov 8, 2004

Wow -- he has a 15k tach? I've never seen one of those.

I would think you'd lose rear wheel traction before actually spinning the engine up this high. Maybe not though.

I drove a 6-speed for over a year (30k+ miles) and never had a downshifting problem. I wouldn't sweat it. Maybe the more appropriate question is if you even need a 6-speed at all...

gp001 · Nov 8, 2004

reenmachine said:
Maybe the more appropriate question is if you even need a 6-speed at all...

What? Everbody needs a 6 speed in their classic

Hack · Nov 8, 2004

reenmachine said:
Wow -- he has a 15k tach? I've never seen one of those.

I would think you'd lose rear wheel traction before actually spinning the engine up this high. Maybe not though.

I drove a 6-speed for over a year (30k+ miles) and never had a downshifting problem. I wouldn't sweat it. Maybe the more appropriate question is if you even need a 6-speed at all...

I think the information is somewhere on this page, if you care to read it all (warning for dialup people - this page is BIG). I was watching some of his homemade movies. I find his writing fun to read.
http://www.nsxfiles.com/stories.htm

Very good point regarding the tach. I found his stories believable, but I have no idea what they put in a NSX for a tach. I expect the number came from the datalogger that he uses to track lateral g forces, speed, rpms, etc, etc. You can see on some of his movies that he superimposes the information on the video - probably a good learning tool. One of the races is on the California speedway and he explains that he was trying to make himself keep the throttle down on the high speed turn (throttle position is recorded and shown on the movie), and he couldn't make himself do it.

Anyway.. the last thing you're probably going to do in that situation is check the tach. I'm sure he was busy trying to keep his car on the track. It probably only hit 15k for an instant before he got the clutch back in.

As far as whether I NEED 6 speeds.. I could always just keep my C4 and I6. I think a 6 speed would be fun. If it isn't very likely that I'll miss a shift, maybe I'll just live with the possibility. After all, more is better, right? Edit: I'm with GP001

reenmachine · Nov 8, 2004

Hack said:
One of the races is on the California speedway and he explains that he was trying to make himself keep the throttle down on the high speed turn (throttle position is recorded and shown on the movie), and he couldn't make himself do it.

Not to get too off topic, but I know what he means. I've raced at CA Speedway with the SCCA, on the infield road course + about 2/3 of the superspeedway. I always lifted just the slightest bit for about half a second on the fastest speedway turn. I'm only going about 125 there in my little RX-7 (compared to what he's probably doing in an NSX) but it is pretty damn exhilirating with that concrete wall flying by right off your right door and some pretty heavy lateral G forces. I'm no NASCAR fan, but it showed me that if nothing else, those guys have balls.

In fact, here's a lap from my in-car video
http://reenmachine.com/pro7/video/FontanaHotLap2004.mov

ratio411 · Nov 8, 2004

I love a T56...
I have had 2.
You do have an extra arm to the 'H' shift pattern of the 4 speed that you have to navigate. Human error can get you compared to a 4 speed, but I have never been able to get into gear on a downshift if I was going too fast for that gear. The shifter just doesn't go or the gears clash when you try... so, IMO, the story of 15k rpm downshift is a fractured fairy tale.
Dave

Fostang · Nov 9, 2004

Definatly B.S.

I went out and tried it.....er not. Couldn't even get the car into gear.

That kinda like saying I got the car into reverse on the freeway. It just won't go.....

Isn't spinning 15K from the crankshaft be different from spinning 15K because of the air/fuel. There is no real stress on top of the rods/pistons forcing the rotating assembly to turn. Maybe could split the crankshaft

ratio411 · Nov 9, 2004

You can downshift into too low a gear if you are just above redline... not 6k above though.
I have heard of folks wrecking their valve train by doing a downshift slightly over redline, then putting the clutch immediately back in. It has something to do with the engine going from a usable rpm to extreme load for a split second, then freewheeling at a high rpm for a second... to much chaos. Broken springs and bent valves are the common outcome with the F-cars.
It is still very rare, and you have to force the car in gear.
The syncros only work for so many rpm, then you can't use the gear.
Dave

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