I’m wondering what people prefer for the number of gears on a manual transmission. Specifically, the non overdrive portion of the final drive ratios. For instance, if 4th gear is DRIVE, would reducing the spacing by making 5th gear DRIVE give me better acceleration, or would the delay from shifting actually reduce my acceleration?
Adding overdrive gears without altering the spacing or ratios of the DRIVE and below gears does not affect performance. I think we can all agree on that. More overdrive gears are always better. You don’t have to use them.
Do 6 speed manual transmissions typically have DRIVE as 5th gear, thereby reducing the spacing between 1st and DRIVE compared to a 5 speed, where 4th gear is DRIVE? Or is DRIVE often still 4th gear, and 5th and 6th are both overdrives?
This is a MANUAL TRANSMISSION WITH CLUTCH discussion. No paddle shifters.
Do not post gear ratios or 0 to 60 times or similar information relating to automatic transmissions, except when necessary for comparison to traditional manual transmissions.
DRIVE will be the name for the highest non overdrive gear. This is the gear where the vehicle can reach its highest speed on level ground.
Overdrive is a final drive ratio that results in a vehicle that is over geared. It is a taller gear ratio beyond what is needed for the vehicle to achieve maximum performance. It exists for increased economy, reduced noise, and reduced wear. For the purpose of this discussion, it has nothing to do with whether a transmission has a lower gear ratio after 1:1. This isn’t even relevant to front wheel drive anyway. See the wikipedia article for further detail: Overdrive (mechanics) - Wikipedia
This thread is actually a remake of this one: Which manual transmission is best, 3, 4, 5, or 6 speed?
To be able to have a proper discussion, we need to agree on what overdrive means, and half of the posts shouldn’t be about automatic transmissions and torque converters.
You have the option to flag the off-topic posts. IMO that’s a better option than starting a new thread. Off topic posts like posting about an automatic when thread is about manual transmissions don’t bother me much personally, easy to ignore. It’s best to never mention certain search features here though … lol …
It seemed like that thread hardly got a response that was on topic. An automatic transmission doesn’t make you cut power while it shifts gears. Nice to know that someone’s 4 speed automatic could out perform their 5 speed automatic. Maybe they haven’t ever driven a manual before, because you have to cut power while the clutch is in to shift gears.
Top fuel drag racers only have one speed. I think some others have 2 speed manuals.
Seems like you wouldn’t want to have to use more than 3 speeds on a manual transmission to get to 60 MPH. It would take too long to shift.
Motorcycles are interesting because they seem to be able to shift gears much faster than a car can. On a 6 speed dirt bike the spead might only be 3.5:1, and that’s considered somewhat wide.
They’re not manual transmissions of the type you’re referring to. Pro class drag racers use manually shifted planetary transmissions that do not require disengaging power from the engine while shifting.
Top Fuel and Funny Cars use a dry centrifugal multi plate clutch system directly attached to the rear axle because they weigh roughly 1800 lbs and make 10,000 hp.
Motorcycles use sequential dog-clutch gearsets that have no syncros. Racecars use this type of transmission as well. Sportscars, NASCAR, and more
I guess I should have been more clear. Professional class drag racers that use a transmission use planetary transmissions.
The top fuel classes USED to use a two speed planetary transmission coupled with a multiple disk slipper clutch.
Traditional manual transmissions haven’t been used in the pro classes for decades, the planetary transmissions are safer and better suited in every respect.
I want to bring my overdrive down to 0.6:1, or add it as a 6th gear. It is currently 0.8:1, or 1.25 times taller than 4th (D). It’s a Ford 4.9L / 300CI truck. edit: 5th might actually be drive where it can reach top speed, so there is no overdrive. I’m not sure, since 90MPH in 4th is pushing 4000 RPM.
As far as performance goes and not using overdrive, It takes a long time to shift, so I don’t know if having 5 speeds from 1st to D would allow me to accelerate faster or not. That way it would probably have to be in 4th instead of 3rd when I get to 60 MPH. It probably takes around 15 seconds to reach 60 MPH as it is. 155 HP isn’t that much. It’s deliberatly sub optimally factory tuned by Ford, it should put out 175+HP).
So much opportunity here but let me just say that any topic that seeks “what is best” has to more acutely define the scope. What’s best for one application almost certainly isn’t best for another.
An automatic doesn’t cut power… perhaps in the same sense that a manual might but by the same token, there is slip and the shift points are designed for particular type of performance that may not suit another use case. Someone can make up for shift time loss by having a more productive power band whereas the traditional automatic shifted so early, it is bogged down until it can reach it’s optimum power band- for example
Anyone well versed in the operation and use of a manual transmission knows how to minimize the shift time required. It’s only relevant for racing and you might be surprised how fast an expert can shift. However, there’s a reason the sport has moved to “automatic” transmissions. Personally, I like to see manuals go head to head because it’s more about the person’s skills then.
Selection for racing always takes into account numerous competing interests- manuals are less mass, have less parasitic losses etc. Automatics have the opposite but are faster shifting. This whole argument doesn’t have a right answer because it depends- it depends on the whole package and how it’s designed to work. I have seen many people with few gears in a manual blow the doors off a purpose built automatic because it wasn’t as well designed and the person using it wasn’t as good a racer…
I have found that a semi automatic, manual valve body transmission works best in my application. It is heavier than a manual and has losses, but those have been minimized by the selection of other components in the car- power band of the engine, gear ratios, torque converter stall speed and so on. In this set up, 5 speeds works well enough. There is always a tradeoff in technology, cost, risk and other factors to consider. Best is relative and highly subjective…
We can try to get more than one half about automatics.
Okay, but if your truck is two wheel drive, IMHO, do yourself a favor, get a remanufactured AOD.
[quote=“TheWonderful90s, post:11, topic:196288”]
since 90MPH in 4th is pushing 4000 RPM.
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You could change the rearend ratio, but that would increase acceleration time.
