Why don't cars use Sequential gearboxes?

Question

I have always felt that the Sequential Gearbox configuration is much much faster than a ordinary gearbox used in cars.

Why is this design used ? Any advantages?

Note: I am aware that racing cars(touring cars & rally cars) use Sequential transmissions, but why not everyday cars?

How does a sequential gearbox work when you come to a stop sign? Is it like a motorcycle where you have to shift all the way back down? If so, I really wouldn't want that in my car... — JPhi1618, Jan 21, 2016 at 13:36
@JPhi1618 In many motorcycles with SEQ gearbox there is a leaver which will pull the tranny to neutral with just one tug no need to downshift through all gears. — Shobin P, Jan 21, 2016 at 13:45
Does an ordinary diver want to go though gears in sequence? Do you? — paparazzo, Jan 21, 2016 at 23:29

DucatiKiller · Accepted Answer · 2016-01-22 01:00:28Z

Some cars have

There was 50's era MG that used them.

I couple of model years of Toyota MR2.

Some reasons manufacturers that have used them and dropped them is user complaints.

It shifts hard.
The consumer isn't used to the idea of going down through all the gears just to get to 1st.
It's louder and sounds unnerving
In BMW's case consumers where allegedly bringing in their cars for warranty when nothing was wrong.

There are claims that they don't last as long as other transmission types although I am unable to validate that.

In car racing, they are very popular

Here's a website that builds them for various classes. GT1 and GT2 WEC are rife with constant mesh sequential transmissions.

Hollinger Racing builds them to swap out the stock transmissions of various homologated vehicles.

But to me, an SMG is music

The main reason most car guys don't use them is money. 10-15k for a sequential box is about 10x what most old fashioned manual transmissions cost brand new. If you throw in the prices on used transmissions, it's an even bigger difference. — Jim W, Jan 22, 2016 at 4:11

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