Final Drive Ratios.

[Nick Mann]

Who understands gearboxes?

The manual gearbox has much lower ratios than the auto, but the biggest difference is the final drive. What chance is there that the final drive is interchangeable? If it is the bit attached to the output shaft, then I think it probably is, but I don't know which bit is which in a gearbox!!

[Nutter_John]

Hi Nick

After the conversation at JF2 I did think about this , it would be great if it could be done , mmmmmm 70 in second would be very nice oh and 100 in third even better :D

[Axeboy]

I find the manual is far too short ratio'd

[Physician]

I'm almost certain it wouldn't work Nick. Certainly from a physical point of view but I would think that it would also totally confuddle the ECU's.

[Nick Mann]

The ECU's shouldn't be a problem. I'm sure Mo had to a bit of trickery to tell the ECU in his auto to not worry that it was now a manual, but not that the gear ratios are different! The speedo should still read correctly, as that is off the output shaft, IIRC, so it doesn't care what the gearing is before hand.

I will take things apart and inspect when I get a chance.

[Physician]

The ECU's shouldn't be a problem. I'm sure Mo had to a bit of trickery to tell the ECU in his auto to not worry that it was now a manual, but not that the gear ratios are different! The speedo should still read correctly, as that is off the output shaft, IIRC, so it doesn't care what the gearing is before hand.

I will take things apart and inspect when I get a chance.

It just crossed my mind ....... do you have a machine shop at your workplace? If so, have a look at the gearing on any mill, grinder or lathe - you should easily be able to identify which cogs are low/high by removing any inspection panel and watching relationship of speed etc.

(I probably ought to shut up now!)

[Nick Mann]

I would imagine when I take the manual box apart I will be able to fathom 1st to 5th. But where is the final drive? It has to be in the gearbox, otherwise manual to auto conversions would need diff/transfer box changes too.

If the final drive is on the other end of the output shaft, then it may be possible to swap.

I have had an auto box apart, but that is black magic to my simple brain! I have also taken apart an old leyland 5 spd manual box, which I understood basically, but this whole final drive thing has me stumped!

[Nutter_John]

I think your right Nick , the final drive must be just before it goes to the transfer box and front drive shafts . If that is the case then you should be able to find the closest to the output and see if it is that one . If not then maybe a gearbox place could look at it as I for one would be will to cough up to have my final drive changed

[bradc]

I'm doing the conversion too, have a search for my thread on final drives and you will see there was no conclusion there either.

If you follow the link to the 3000gt site then you can see it is even more difficult, with different ratios all over the place! I think we may be best until mo tells us what rpm his car runs at when he is doing 60mph

[bradc]

Forgot to put this up, here are the speeds you will run at if there is no funny primary ratios or anything like that.

As you can see a manual with a 3.684 final drive would be able to reach 100kmh in 2nd gear, as well as cruise at a lower rpm

[Nick Mann]

No go, I'm afraid. The design is the same, but the shafts are further apart in the auto, so the spacing is incorrect to swap the final drive gears over. Bugger. I would imagine it is possible to get them specially made, but that would cost a fair bit I guess!

[bradc]

so this ratio that you're talking about, where is it? is it in the bottom of the gearbox itself?

My car already has the manual box in it, so they must have got it working, but it sounds like it will run with a 4.111 final drive

[Nick Mann]

The Evo manual looks identical to ours, except for the bellhousing. So I can borrow the pictures here (http://www.lancerregister.com/showthread.php?s=&threadid=94981) to explain.

The third picture shows the box with the bellhousing removed. The input shaft is closest to the viewer (complete with rusty splines!) the lay shaft (forgive me if I have the incorrect technical term) is the next shaft in, the output shaft is missing from it's seat due to the fact the guy had snapped it!

The final drive is the small gear at the top of the lay shaft, plus the large gear on the output shaft that is laying on the work top.

The design in the auto box is almost identical - indeed the large gear is the only part of the output shaft that is different. You could easily put the auto output shaft in the manual box BUT because the lay shaft and output shaft are further apart in the auto, the gears are too big to fit on each other in the manual.

So two gears with the correct number of teeth in those positions could give you any ratio you want - there is plenty of room for bigger/smaller gears. But as fas as I know there is no option of a longer ratio for the box - the evo guys have a couple of options, but 4.11 is the longest version they have. This looks to me like you would need to have the final drive gears made as a one off. I would imagine that is a tad expensive!!

[bradc]

ok cool.

next question - in a 3000gt for example there are ratios in the transfer case, front diff and rear diff, do you know if there is any chance if the ratios in those parts are different between auto and manual?

[zentac]

Sorry Ive not read this sooner, I spent almost 12 months researching gearboxes and ratio's for the FTO, and still have at least 2 gear boxes in pieces kicking round that I need to rebuild and sell.... to cut a long story short my FTO use to have a ratio of

1st = 3.583
2nd = 1.947
3rd = 1.379
4th = 1.030
5th = 0.820
Final = 4.312

and now have

1st = 3.583
2nd = 1.947
3rd = 1.379
4th = 1.030
5th = 0.767
Final = 3.722

The internals from the Galant V6-24V, you would have to do some digging but Im pritty sure these would fit the VR4 box and give you the ratio's your looking for.

Top Speed in 1 gear = 37.739 MPH
Top Speed in 2 gear = 69.450 MPH
Top Speed in 3 gear = 98.056 MPH
Top Speed in 4 gear = 131.280 MPH
Top Speed in 5 gear = 176.296 MPH

As for the power, I think Im running more than anyone else here and hammering it more (no daily driving though) and they have held up to everything Ive given them including lots of 4000rpm launches.

[Nick Mann]

Richard - do you have the final drive ratios from the V6 lying around? Or are the only ones you have in your gearbox? Do they look the same as the ones on the MLR thread linked above?

[zentac]

The only ones I had are in my box, for the final drive you need the Diff and the main staft (which gives you the final drive) you could just replace the diff but you need to know how many teeth it has, you may get away with just replacing that for an FTO one or a Galant one.... CAPS actually tells you how many teeth are on each cog so I will check later.

[bradc]

The ratios for a vr-4 manual are as follows:

3.333
2.105
1.407
1.031
0.761

4.111


I think the gears themselves are spaced apart just fine, the big problem is the final drive ratio is too high, it would be nice to change to the auto box's ratio.

If we change the main shaft, will it actually mesh ok with the diff? Remember it is more difficult for us to change our diff because of the 4wd system, Ideally we would want to change it by either changing one of the shafts in the gearbox.

[Nick Mann]

Brad - check the pics in the MLR thread. Surely the diff is the bit that the large gear for the final drive bolts to? If it is then the diff is easily swapped, if it needs to be. I think the big problem is the gear wheels that form the final drive ratio. If the V6-24 manual gears will work then we may be on to a winner. Does anyone have a knackered V6-24 box lying around that I can take apart?

[bradc]

but if we change the gear on the diff won't that screw up the speed at which the front and rear wheels spin, and screw the whole system?

[Nick Mann]

Just changing the final drive ratio shouldn't mean you have to change the diff. The final drive ratio has all the power travelling through it - the splits for each wheel occur later - so just changing the final drive should not affect the splits to the wheels.

[bradc]

but if you look at their pics, they are talking about a diff, to me it sounds as if the final drive cog joins straight up to a diff, or am I wrong?

[Nick Mann]

It is bolted to the back of the diff assembly (if I am correct, and I'm no expert!) but I don't see why that should make any difference? The power/torque is not split until after the final drive gear.

[glyn]

Sorry Ive not read this sooner, I spent almost 12 months researching gearboxes and ratio's for the FTO, and still have at least 2 gear boxes in pieces kicking round that I need to rebuild and sell.... to cut a long story short my FTO use to have a ratio of

1st = 3.583
2nd = 1.947
3rd = 1.379
4th = 1.030
5th = 0.820
Final = 4.312

and now have

1st = 3.583
2nd = 1.947
3rd = 1.379
4th = 1.030
5th = 0.767
Final = 3.722

The internals from the Galant V6-24V, you would have to do some digging but Im pritty sure these would fit the VR4 box and give you the ratio's your looking for.

Top Speed in 1 gear = 37.739 MPH
Top Speed in 2 gear = 69.450 MPH
Top Speed in 3 gear = 98.056 MPH
Top Speed in 4 gear = 131.280 MPH
Top Speed in 5 gear = 176.296 MPH

As for the power, I think Im running more than anyone else here and hammering it more (no daily driving though) and they have held up to everything Ive given them including lots of 4000rpm launches.

did you ever get anywhere with this? I have an evo 4 box on my legnum, gearing is all to pot! I also have a v6 24v gearbox, so just reading your comment I got a little excited to think I might be able to do some changes without spending money I don't have, thanks in advance for any help, I know literally nothing about gearboxes if im honest but I do love my car an do my level best to keep it out of the car cemetery lol