Can you mix gear ratio's

[munchie]

Hi can anyone help? ive bought my girlfriends old Nova GTE, she found the gear box a struggle so after a lil nagging we found a newer one off an Astra 1.3 or 1.4. Well since ive been using it ive noticed something which at first was strange, i raced a RS Turbo home from work and literally played with it, the next day a 16v GTE Astra then a 16v Vectra, no problem, the fact was the new box gave me ridiculous acceleration, 325i BMWs and the newer 328i's beaten to 120mph even on the way back from Plymouth with 4 up, the thing is Ive had 3 GTE's and know the top end to be pretty good, is it poss to take 5th from a GTE box and fit it to the one thats in the car now? as i can hit 125mph in 4th now but no more in 5th. (would my speedo be out?)
the other thing is My mate and i went to London in it and managed over 60mpg can that poss be right? we came back all the way pretty much flat out!! Perhaps i smoked too much weed over the years and cant add up!

[MC]

Sounds strange, the box you have shouldn't help with acceleration, in fact it should make things worse. If you can do 125 in 4th, then you have a long ratio box which is a waste of time if your car hasn't got the power to use it, i.e. can go no faster in 5th than 4th. Idealy you need a box that matches your top speed, say a 5th gear that hits about 6,500 and 130ish mph, then each gear between would be closer together and would ensure revs don't drop too far below peak torque for each change. The best combo I've found so far is the FD from a box like yours (should be 4.18:1) with the cluster from a close ratio box, although I think there might be closer combination out there.

Oh and you are right about mpg. The long box will mean your revs will be lower when cruising in 5th, needing less throttle and using less fuel.

[cornish]

MC what gearbox where you using on your old 1.4SR when you had 40's etc..?

[MC]

I was using the original F10CR, it topped out at 130ish in 5th.

On my 1600 I eventually settled for the F10CR ratio's with the FD from the F13WR (4.18). It brought everything down a bit. I had to rev to about 7500 to hit 130mph.

[Dave_Hay]

im really starting to threadjack now lol
neway i wanted to know what was the car like to drive with modded gear ratios? im presuming very loud and not to nice for cruising? worth while mod for the track tho?

how much did it cost to have the final drive swapped over as well? cos its quite complicated aint it?

[MC]

Cost? Whats that?

Nope, Cp and I did all the work ourselves. It's not as complicated as most people think. You need to have the driveshafts out, undo all the bolts on the end plate and the whole cluster pulls out. The gear ratio's are fixed per cluster, but the FD pinion can be removed from the end of the shaft. Just remove the Circlip. The Crown wheel doesn't change.

Driveability - Sweeter gearchange, i.e. less revs dropped. Revs slightly higher when cruising, but it still had a fairly decent top speed. No noisier, I didnt have any carpet or soundproofing anyway, and the Carbs were loud enough.

[CP]

With these gearboxes all you can realistically do is swap std.clusters and/or the crown wheel and pinion sets around. Swapping gears around within the cluster isn't possible from 1st to 4th and I don't think there are any different 5th gear ratio alternatives anyway. This means that you will either have to get your own cluster made up (v. expensive) or buy a comp. cluster but since most of these tend to be for rallying you will probably find that they are a pain for ordinary road use as they drastically curtail top speed and are noisy.
The best is what MC says if you like a nice sporty feel and improved quarter mile times. F10 out of a 1.4Sr with the 4.17:1 Crown wheel and pinion out of a 1.6 GTE/GSi (assuming its running the wide ratio box which can be spotted by the wide gap between 3rd and 4th and finding that top speed is usually achieved in 4th not 5th cos 5th is so high)
It is an area worth looking at cos when you watch cars going up the strip its noticeable how inappropriate the ratio's are in most std Vaux boxes are, particularly 3rd to 4th.

[rgv_stu]

is it just the wide ratio gte boxes that have the 4.17:1 in it? or do all wide ratio f13 boxes have them?

[MC]

Most wide ratio boxes will actually have a close final drive. Best thing is to read through the haynes manuals for all the Novas astra's cavs etc, and decide which will be the best combo. I think there is a cav box that has a 4.34 FD.

[rgv_stu]

arnt the gearboxes supposed to have the final drive stamped on them on the end casing??

if so i cant find mine

[Breeny]

Driveability - Sweeter gearchange, i.e. less revs dropped. Revs slightly higher when cruising, but it still had a fairly decent top speed. No noisier

I can agree with that :)

[Dave_Hay]

lecturer at uni was talking about gearboxes and said every cluster has to be pressed in and pulled out, with the way the gearbox is made i thought it would be quite tricky to swap the clogs or teethed wheel whatever u wanna call it, im also presuming u just took off top cluster and replaced the final drive ratio teethed wheels?.
no probs with the modded box at all then? no whining or nowt?

or am i speaking shite ere and i should shut up and stop confusing every1.

[CP]

lol! No dave there are no clogs to be swapped in a gear box!
Its not that difficult actually. Although there is quite a bit of work to get it all prepared the actual changing of the cluster is a matter of undoing the end plate which is held in by about a dozen bolts and then prising it off its dowels. The cluster itself comes out connected to this end plate in one lump. It comprises of 2 shafts which have the various cogs on them for each gear. One is called the input shaft and is the one that is splined to go into the clutch. The gears on this shaft mate with gears on the other shaft known as the output shaft. In between the gears are the synchromesh gear selectors. If you twist input shaft and slide these various synchromesh selectors back and forth you will see how the out put shaft speed is altered relative to your twisting speed as diffrent gears are selected. It is all self retaining and there aren't a load of bearings and cogs to fall out all over everywhere.
The pinion cog( the small cog which drives the large cog - the crown wheel) which controls the final drive ratio is located on the end of the output shaft and held on by a circlip which is a doddle to swap. The crown wheel can be abit more tricky to get out as it has the differential attached to it and there's not much room to remove it. Once thats out its just a question of unbolting the crown wheel and swapping the new one onto the diff

[Dave_Hay]

agh i was on about the actual gears, my apologies.

its a piece of piss then :P

[cornish]

Anyone got any info on the Corsa F15 box?

Whats the ratio's and spacing like, worth putting on a 1.4SR?