Overdrive

[martin.herwitson]

Hi all,
just bought another Silvia as a restoration project and was intending to swap it from auto to manual G/box but having driven it home I'm not so sure if that's the best idea. The auto box makes Silvia a much better motorway cruiser 2700-2800rpm @ 80mph with overdrive on! Makes me wonder why Nissan never fitted an overdrive option to the manual.....did they?

[PukkaSilvia]

the motorway limit is 70 martin

[martin.herwitson]

Did I mention that I picked it up from Berlin?......Obviously

[zxocmars]

Originally Posted by martin.herwitson

Makes me wonder why Nissan never fitted an overdrive option to the manual.....did they?

The overdrive option on a manual is called "5th"

O/D wouldn't work with a manual box, I'm not sure why, i think because it would then be a 6th gear.

[30psi]

5th is over drive, purely because its over driven.

Worth checking your speedo against GPS but chances are your doing closer to 70mph even if the speedo is saying 80

[sideways danny]

Originally Posted by 30psi

5th is over drive, purely because its over driven.

yip, 1,2 and 3 are underdrive, 4th is 1:1 and 5th is overdrive.

the auto is fine and makes the s12 a nice car to drive, ideal daily driver infact. not overly exciting though and I wouldn't bother with tuning an auto at all

[old-and-rusty]

Originally Posted by sideways danny

the auto is fine and makes the s12 a nice car to drive, ideal daily driver infact. not overly exciting though and I wouldn't bother with tuning an auto at all

I would second that. My s12 (when she was running) had an auto box. I tuned her up to just over 200 bhp at the wheels, but the auto box couldn`t handle the extra power. Kick down and the car would red-line before the auto box had chance to catch up with engine speed.
I had to have the box reconditioned three times cos it kept blowing seals .

Great motorway cruiser though and still very quick (when she was on the road ).

Regards,
Ian.

[Ronin]

Originally Posted by zxocmars

The overdrive option on a manual is called "5th"

O/D wouldn't work with a manual box, I'm not sure why, i think because it would then be a 6th gear.

You can get O/D on manual boxes I've drived old V6 Scimitars GTE with a 4 speed manual with O/D. I sure there were BL cars with the same sort of boxes.

[30psi]

A 5 speed box is a 4 speed box with O/D, its just a different marketing method to describe them

[Ronin]

The Scimitar box had a button on it you had to press to engage O/D so you would have 1st, 1 1/2 (O/D), 2nd, 2 1/2 (O/D) and so on up the box. If you've seen Mark Evans An MG is Born on Discovery he fitted a similar box to the MG B he built and he actually went to the place where the boxes are made/reconditioned.