overdrive unit

[vicelore]

Hey guys just been watching " a MG is born" by that mark evans chap. good show if anyone has seen his a 4x4 is born.

anyways just learnt what a overdrive unit does. sounded like it could switch gear ratios on the fly. got me thinking can you add such a device to a sierra box ? make it work in 1st and 2nd ? he said it only worked in 3rd and 4th . is this a crazy idea ? im sure someone has thaguht about it before ???

well just interested . Cheers guys

[lay80n]

Over drive units are usually employed to basically give a 4 speed box a "5th" gear to make crusing better. E.G. Fairey overdrive etc for landrover. Makes cruising at freeway speed (which is a bit higher than when the vehicle was origionaly made) economical and less straining on the motor. In a sierra the application is pretty useless, due to having a 5 speed and no much power anyway. If you want to lower your gearing - get t-case or diff gears. Overdrives are more dsigned for freeway speed cruising.

What are you wanting out of a overdrive.

Layto....

[vicelore]

yea i knew that they where used for high speed. but isnt it really a unit that for example. turn a shaft from doin 1 turn to maybey 1.4 turns per revolution. therefor lowering the gears at the flick of a switch

Cheers

[lay80n]

Not worth the effort or $$ when t-case and diff gears are so readily available, esp as 1.4 is fawk all really, when you can go a 6:1 or so reduction in the t-case so easily as well as diff gears, or upgrade diffs and axles etc.

Layto....

[want33s]

yea i knew that they where used for high speed. but isnt it really a unit that for example. turn a shaft from doin 1 turn to maybey 1.4 turns per revolution. therefor lowering the gears at the flick of a switch

Cheers

Check the bible. I'm sure theres threads on Fairey overdrives/Lada transfers etc but I think you want an underdrive not overdrive, and no you shouldn't fit an overdrive in backwards as gear/bearing damage will result.

[Jock]

There is a box trhat replaces the jack shaft.

http://www.trailtough.com/transfercase_driveshaft.htm

It is called the "Rock Block - Intermediate GR for Suzuki Samurai"

[Gwagensteve]

Sorry for the hijack -

This is trail toughs roc-bloc and it is the low range gearset from a vitara installed in the jackshaft area.

Interestingly, trail tough list these as "for offroad use only" which makes me wonder if they cook or vibrate if used at highway speeds.

I actually think this is a bit like dual transfers- it answers a question that nobody really asked. - If you have enough traction and tyre size to warrant a really low low range, you won't be able to really use stock sierra or vitara low range anywhere.

If you regear your diffs to 5.12 or so, maybe, but the work doesn't seem to make it worthwhile - just stick a 6:1 in it and call it good.

with much bigger cars with more torque and power, I can sort of see it.

Steve.

[droopypete]

Over drive units are usually employed to basically give a 4 speed box a "5th" gear to make crusing better. E.G. Fairey overdrive
Layto....

I may be wrong but I think you will find a "Fairey" overdrive was in fact a "gear splitter" effectively giving you a "half gear" above all existing gears, not just 4th.
Peter.

[lay80n]

Over drive units are usually employed to basically give a 4 speed box a "5th" gear to make crusing better. E.G. Fairey overdrive
Layto....

I may be wrong but I think you will find a "Fairey" overdrive was in fact a "gear splitter" effectively giving you a "half gear" above all existing gears, not just 4th.
Peter.

Your right, my explenation could of been better. Will give you a gear between each.

Layto....

[droopypete]

Your right, my explenation could of been better.
Layto....

Yeh, you suck aarse
I thought you would have been an expert on "fairys"
Peter.