speed

[richierich]

Hi, well thanks for all the help with my gearbox ive just put an 8p box in for the moment while i save up for a diff.

the problem im having now is ive put this 8p in and i was told 5th gear is longer and been lookin at some youtube videos and took the g to 120mph but it was at 6k and in these videos 120mph is achieved at 4500

now i wanted an 8p for motorways to keep the revs down so what do i need to do? any ideas? the only thought was that final drive is defferent but dont know enuf?

also doubt this will do 147mph that im told 8p boxes can do

thanks richie

[PeteG40]

8p is shorter overall than an atv g40 box.   I think the 8p 5th is longer but the different final drive makes it lower overall

[richierich]

thought it may be somthing like that but best ask,

sooo if i rebuilt the atv box using the 8p fifth is this going to be the best way?

thanks richie

[PeteG40]

apparently thats been done before and then its a huge jump 4th till5th

[richierich]

yea the videos i wached on youtube was like 120mph in 4th then the revs droped to around 4k in 5th!

what kid of revs is a standard box ie 5th at 80mph equals if you have any idea?

[breadman]

8p is shorter overall than an atv g40 box.   I think the 8p 5th is longer but the different final drive makes it lower overall

This is exactly right, I can't see the reason to raise the gearing any higher than the ATV box.
The standard gearing will allow circa 150+mph - power permitting of course. Cruising at 90 - 100mph is easy even in standard form.
IIRC, 80mph is about 3400rpm in 5th.

[richierich]

ive got an atv box in bits at the min just wanted to know whats best for it because even when i was running the atv box it felt like i needed another gear and herd on clubpolo to use an 8p as 5th is longer

what do you recomend doing as im going to build the atv but was goin to put the 8p fifth gear on it and still use atv final drive? what doya think?

thanks for the help richie

[breadman]

As Pete said, you can do it but it'll be a big jump from 4th to 5th gear which is hardly ideal.
What tyre size are you using?

[richierich]

i may do that then as my atv 5th is screwed anyway!

youll have a giggle at the tyres there 175/50 13s

i understand thats gearing it up but i would think the speedo would be the speed that the car in theroy would be doing if the tyre size was right so its just the road speed thats out??

[Justin14100]

i saw some numbers somewhere once and its a really, really big rpm change - adds another 30mph to the top speed at 6500rpm though

[richierich]

Awsome thats kinda what i want lol running 13's it should make it a little betta on motorways.

also whats the best way to remove 5th gear of the input shaft in the gearbox as when i removed it from my atv i was being carefull and still managed to snap 2 teeth off 

thanks richie

[G40supercharged]

Standard G40 5th gear is about 21.6 mph per 1000rpm which comes out as 140mph at stock rev limit of 6500rpm. That gives 3700 rpm cruising at 80mph. Speedo drive is taken from the diff output so it will read correctly regardless of the diff fitted (eg GT box is different final ratio to G40 but speedo will read OK if you fit one. On old RWD cars the speedo drive was normally from the gearbox output shaft so any diff change needed a different speedo.) Your small tyres aren't helping though.

[lazy]

Has anyone got a vag part number for 8p 5th longer gear?