Manual Gear Box VR-4 Owners - Do you feel the gearing is too short?

[bradc]

Who here with manual gearboxes feels that the gears are too short? I was thinking that if we could get enough people together we could change the final drive gear that goes from the transmission to the transfer box.

The current setup is below with the autobox first, then the manual. Both with their stock final drives. Then we have a manual gearbox with an auto's final drive, and lastly the evo 8 6 speed gearbox with the auto's final drive.

I think that the Manual gear spacing is ok, it just needs a slightly longer final drive and I think that 3.684 is about right. Now we know that the auto box's final drive gear will not fit into a manual box, so we need to get some custom gears made up.

Who's keen?

[Axeboy]

I agree, it is quite short for a car with so much torque.

[Nick Mann]

I would be interested, cost dependant.

[Nutter_John]

Tell me where to send the money

[stuey]

manual could definately do with a 6th gear... Replacing final drive would do it, as said torque is there for existing gearing. May be interested

[valmes]

It's short...

[bradc]

Sounds like I've got 5 confirmed orders

Now, what gearing do we want? Looking at the table there would the 3.684 final drive ratio make everyone happy? Or would people want other values?

[Nutter_John]

3.684 looks about right to me , don't want to make it too long

[Kenneth]

depending on cost (of course) I would also be keen

[Nick Mann]

I would like it slightly longer if poss. Not too much, maybe closer to 3.5. Any chance of a speed chart in MPH comparing it all? I have tried, but my formula must be slightly wrong, as the top speed in each gear seems slightly too high!

[Kenneth]

I would like it slightly longer if poss. Not too much, maybe closer to 3.5. Any chance of a speed chart in MPH comparing it all? I have tried, but my formula must be slightly wrong, as the top speed in each gear seems slightly too high!

you divide KPH by 1.6 to get MPH

[Nick Mann]

See? They seem just too high? Or maybe I am not allowing for the fact that I tend to change at 6700 rather than 7000? What do you manual boys think? Are your ratios about right or do they seem high as well?

[Nutter_John]

All at 7000 rpm on standard drive with 235/45/17


3.8640

3.3330 41.0699
2.1050 65.0290
1.4070 97.2893
1.0310 132.7702
0.7610 179.8765

3.5
3.3330 45.3412
2.1050 71.7920
1.4070 107.4074
1.0310 146.5783
0.7610 198.5837

3.333
3.3330 47.6130
2.1050 75.3892
1.4070 112.7890
1.0310 153.9226
0.7610 208.5337

[Nick Mann]

Ahh.... Okay. My calculation is good - my numbers are in fact slightly lower than Brads, which I guess is because I used a 225/45/17 tyre not a 235.

I would prefer the gearing to be slightly longer than the standard auto box, which I think is still a bit short, so I will stick with my request of closer to 3.5 for the final drive ratio. (Still cost dependant!)

[Nutter_John]

3.5 final Drive would be very good , enuf to do full 0-60 in only 1st and 2nd without slamming into redline

Come on Brad get it sorted with some prices

[EdmundVR4]

I've noticed that on manual & automatic transmission versions of the same model cars that the auto model always revs lower at the same speed.
Might there be a reason for this ?
On another note, when I converted my 7G VR4 to GTO engine, gearbox & transfercase, I screwed up the VCU because I was using a 3.9 rear diff instead of a 3.545. I have since fixed the VCU and replace
d the rear diff to a 3.309,then to 3.545 upon learning 3.545 is the correct ratio. All is well now, but I learnt the hard way that the front, middle & rear gear ratios have to match each other. (don't know if the same applies to the 8G scenario described above)
I would also be interested in the 3.684 final drive.

As an aside, the 6th gear (.59 ratio)in my 7G is no good for quick overtaking under 125km/h, I almost always downshift unless I'm feeling lazy or there is quite a bit of space. (Three overdrive gears, 4th 0.918, 5th 0.733, 6th 0.589)
Enough rambling.

[Nick Mann]

The only point there that I can reply to is the frot/rear ratios. These will stay the same, as the final drive is in the gearbox housing, between the lay shaft and output shaft. Thus changing the final drive will not affect the ratios after the gearbox, as they all split off the output shaft.

Also, the speedo should remain calibrated, as all it is doing is reading the speed of the output shaft.

It sounds like your 7g has MUCH longer gearing than the 8g. What is your speed per 1000 revs in 4th/5th/6th? And what is your 6spd box from?

[EdmundVR4]

^^^ 4th, 5th & 6th are overdrive gears as you can see. Good for the Autobahn
R&P 1st 2nd 3rd 4th 5th 6th Gear
4.15 3.27 1.90 1.24 0.92 0.73 0.59 Gear Ratio
RPM MPH MPH MPH MPH MPH MPH
2000 11 19 29 39 49 61
2500 14 23 36 49 61 76
3000 16 28 43 58 73 91
3500 19 33 50 68 85 106
4000 22 37 57 78 97 121
4500 25 42 65 87 109 136
5000 27 47 72 97 122 151
5500 30 51 79 107 134 166
6000 33 56 86 116 146 182
6500 35 61 93 126 158 197
7000 38 66 101 136 170 212
8000 44 75 115 155 194 242

[bradc]

I don't Trinidad and Tobago has an Autobahn hehe.

Nick, as you said the final drive gear is in the gearbox. Is there any chance that someone with Caps could find the correct part codes for the actual gear itself, as well as the other gears either side of it, plus put up a picture?

I need to be able to see how it all goes together so we can work out which gears need to be changed. I doubt it would be possible to just change one because that would create meshing problems etc, so we might need to do something like increase one cog by one tooth, and decrease the other by one tooth as well. If that doesn't change it enough, then we can go for 2 teeth on each cog.

[Nick Mann]

Don't forget that the angle (helix?) of the teeth can change too. I don't know enough about gears to say anything for sure, but I think this could allow for more options than just increasing/decreasing the number of teeth on each? I think the design will be the expensive part of this exercise, rather than the manufacturing.