yeah i was just thinking, it will only reduce top speed if you could reach the limiter before. else it would be about the same.

 

lmao lmao lmao
odders you amaze me where u get all these pics from..

yeah thats the nut i was on about. last time i took it out, i tried that method, but just ended up breaking the teeth off one bye one.

you can just use a piece of flat steel across the driveshaft hole to undo it, remember to mark it though, as diffs have a specific pre-load which is adjusted by how tight you do up this nut

 

you can just use a piece of flat steel across the driveshaft hole to undo it, remember to mark it though, as diffs have a specific pre-load which is adjusted by how tight you do up this nut

which wont be the same when you do it up again, need to use a torque wrench with some kind of adapter to reach out to the teeth.

 

why wouldnt it be the same? if you are only changing the final drive, not the bearings, could be wrong but thats what the haynes says

 

Stes diagram is less than useful, where the hell is the number??

anyone got a photo with the number highlighted??

 

yeah i was just thinking, it will only reduce top speed if you could reach the limiter before. else it would be about the same.

Well sort of. It depends on how much you lower the ratios. I couldn't reach my limiter before - I could get to 6200rpm and the limiter is 6600rpm or similar. Now I can bang onto the limiter, obviously at a lower speed.

 

Stes diagram is less than useful, where the hell is the number??

anyone got a photo with the number highlighted??

what number? what you on about ? theres isnt 3.5 or 3.9 stamped anywhere, that number is just teh amount of teeth on the crown wheel divided by teh number of teeth on the pinion

i.e 71 teeth crownwheel, 20 teeth on pinion = 3.55:1

 

If you have a wide ration F16 with 3.55 then going to 3.94 will improve:
1. Acceleration and drivibility.
2. Improves top speed as well.

You will loose on top speed only if you have a F16 close ration and do the same thing.

I swapped my old wide ration F16 with 3.55 with a new one from a scrap yard for 50 quid with 3.94 ratio and I will never go back. The results are amazing. I never thought swapping a tired gear box can enhance things so much.

So if you want a 3.94 diff go and get a F16 box out of a 1.8 Cav, but use the codes mentioned in above posts just to be sure the final drive ration is what you want.

So how are the final drive ration made? Is the diff crown the same and the ratios are controlled by the gearing in the driveshafs gears?

 

i get the count teeth and divide idea. ive not waisted 3 years at uni for nothing lol (appart from not learning to spell and to get skint)


i mean the gearbox number thats stamped onto the casing. bit like an engine number and chassis number and any part number thats on an item, but in this case selected especially for a gearbox, making it a gearbox number

 

well the F number is ontop here...

ive yet to see a car with that number on the endcase as ste_sa pictured.

 

While on the subject of Gearbox's.

I have an F18.
Anyone know the ratios and FD and
I'm presuming the gearbox internals
would fit into a F13?
As they seem a similar size.

Sorry for hijack.

 

If you have a wide ration F16 with 3.55 then going to 3.94 will improve:
1. Acceleration and drivibility.
2. Improves top speed as well.

How does it improve top speed? You're not making any more power. With the WR boxes, sometimes you will make higher top speed in 4th rather than 5th. Or is it because lowering the final drive causes the engine power to match the speed better. ie: drag power and wheel power curves cross at a higher speed?

 

just had a look at a spare f16 i have from a 2.0 8v cav sri, how do u know wheather its a cr or wr box?

can u tell the final drive, without stripping the box to bits?

 

2. Improves top speed as well.

On the 2.0 Cav 3 WR, 3.55 ratio, peak power at 5.5K will generate a speed of 150mph, clear not possible with a 130bhp car. However with a 3.94 ratio the speed at 5.5K is about 135 which is more usable speed. True, you may be able to go faster in 4th with the 3.55 box, but from experience I was not getting any faster in fourth then in fifth with my old 3.55 box. Also the higher the revs the more loses are incurred in the gearbox, so a slight overdrive fifth (which the 3.94 ratio is) should in practice improve top speed, and this is what I am experiencing after swapping the box.

 

just had a look at a spare f16 i have from a 2.0 8v cav sri, how do u know wheather its a cr or wr box?

can u tell the final drive, without stripping the box to bits?

2.0 8V sri, should be CR and 3.55. But check the markings on the box and use the coding described in this post above to confirm.

 

Im running a f20 with the 3.42 with a quaife gearkit now Christof.Why not do that?Mine wines like f*** now .Sounds better than a touring car!

 

as odders says, non of the markings described above are on any of the boxs?

 

as odders says, non of the markings described above are on any of the boxs?

had trouble finding them on my box too, didnt think they were there at all till i scraped the dirt away and sanded the end casing a bit, found the number buried under 10 years worth of crud

 

where exactly did u finfd the number?

 

if you look on ste's diagrm, my number was just by the end of that arrow, by the join between the end casind and the intermidate section of the g/box

 

I've just been reading this thread, very interesting when and where I can understand it! According to my Astra haynes, the F16 5 speed wide ratio already has the 3.94 final drive on it. Anyone still worrying about this FD business, go get one off an astra!

Would this be the best box to use on my car, then? I have a F10 5sp wide ratio with FD=4.18. :beer:

 

cant use small block final drives, because the pinion is detachable. but on F16/F20 the pinion is the basis for the whole gear set.

basically they arent interchangeable.