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Austinsevenfriends
4 speed gearbox ratios - Printable Version

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4 speed gearbox ratios - wooster - 15-10-2018

Hi All
I rarely use 1st while driving my Ulster rep. It pulls away in 2nd with no problems. And fourth always seems a bit short (I mean it feels like there ought to be a 5th). Is it possible to have the gearbox modified, to alter the ratios to make 1st usable and 4th higher?
Cheers
Rich

RE: 4 speed gearbox ratios - Tony Press - 15-10-2018

(15-10-2018, 09:21 PM)wooster Wrote: Hi All
I rarely use 1st while driving my Ulster rep. It pulls away in 2nd with no problems. And fourth always seems a bit short (I mean it feels like there ought to be a 5th). Is it possible to have the gearbox modified, to alter the ratios to make 1st usable and 4th higher?
Cheers
Rich

Fit an overdrive ?

RE: 4 speed gearbox ratios - Ruairidh Dunford - 15-10-2018

Fitting a 4.9:1 ratio back axle will probably get you nearer to where you want to be.

RE: 4 speed gearbox ratios - Chris KC - 15-10-2018

Or 19" wheels, if you are running on smaller rims

RE: 4 speed gearbox ratios - Robert Leigh - 16-10-2018

(15-10-2018, 09:21 PM)wooster Wrote: Hi All
I rarely use 1st while driving my Ulster rep. It pulls away in 2nd with no problems. And fourth always seems a bit short (I mean it feels like there ought to be a 5th). Is it possible to have the gearbox modified, to alter the ratios to make 1st usable and 4th higher?
Cheers
Rich
On my Ulsteroid I fitted some higher ratio primary gears in the gearbox. They are straight cut from Keith Rawson, so it whines in anything but top gear, but I can get the speedo past 60 in third with corresponding increase in first and second. With these gears it usually best to start in first, but I am general very happy with the set-up.

RE: 4 speed gearbox ratios - Stuart Giles - 16-10-2018

This chap does 4 speed as well as 3 speed gearboxes. http://austinsevengearboxservices.co.uk/services/4590369273 -usual disclaimer-
The numbers on the website are the tooth count of the 1st motion shaft and laygear. The faster the layshaft is driven, the closer the intermediate gears come to the 1:1 top gear. If you do significantly raise the overall gearing, 4.9:1 CW & P and/or bigger wheels, you may find the large ratio gap between 3rd and 4th on the standard 4 speed 'box becomes more noticeable.

RE: 4 speed gearbox ratios - Chris KC - 16-10-2018

If top gear feels too low, the final drive ratio needs to change, no amount of tinkering with the gearbox will change that. Once top gear is where you want it, review the suitability of the intermediate gears.

For 'performance' driving a CR box is likely to feel better on the road, at the expense of some capacity for 'crawl' and mountain ascent perhaps.

RE: 4 speed gearbox ratios - Tony Press - 16-10-2018

(16-10-2018, 06:16 PM)Chris KC Wrote: If top gear feels too low, the final drive ratio needs to change, no amount of tinkering with the gearbox will change that. Once top gear is where you want it, review the suitability of the intermediate gears.

For 'performance' driving a CR box is likely to feel better on the road, at the expense of some capacity for 'crawl' and mountain ascent perhaps.

As I said- with a one to one top the only way to change the gearbox is fit an overdrive !!

RE: 4 speed gearbox ratios - Zetomagneto - 16-10-2018

(16-10-2018, 09:42 PM)Tony Press Wrote:
(16-10-2018, 06:16 PM)Chris KC Wrote: If top gear feels too low, the final drive ratio needs to change, no amount of tinkering with the gearbox will change that. Once top gear is where you want it, review the suitability of the intermediate gears.

For 'performance' driving a CR box is likely to feel better on the road, at the expense of some capacity for 'crawl' and mountain ascent perhaps.

As I said- with a one to one top the only way to change the gearbox is fit an overdrive !!
Someone will suggest a five speed box in ha minute.Higher axle ratio needed.

RE: 4 speed gearbox ratios - Chris KC - 16-10-2018

(16-10-2018, 10:28 PM)Zetomagneto Wrote:
(16-10-2018, 09:42 PM)Tony Press Wrote:
(16-10-2018, 06:16 PM)Chris KC Wrote: If top gear feels too low, the final drive ratio needs to change, no amount of tinkering with the gearbox will change that. Once top gear is where you want it, review the suitability of the intermediate gears.

For 'performance' driving a CR box is likely to feel better on the road, at the expense of some capacity for 'crawl' and mountain ascent perhaps.

As I said- with a one to one top the only way to change the gearbox is fit an overdrive !!
Someone will suggest a five speed box in ha minute.Higher axle ratio needed.
...or a larger tyre rolling radius.