Final Drive gearing change?

Note that the cascade gears are not the best place to save money. The damage they can cause if something goes wrong can be extremely expensive to repair. I would leave this to the specialists.

 

Yeah, but I've never been accused of having much sense...and if it the boost wasn't turned up to 22 psi (which can also cause expensive damage), I guess I wouldn't need the gears to begin with...it's a vicious cycle

 

We can do them helical, that's the only way I'd do it for a road car.

Same pricing. Get 10 orders together and it's $3000, no headaches to engineer yourself.

Rob

 

hmmm...now I just need to find 9 more people. Do we all need to order the same ratio? How low a ratio can the set be made, i.e. mph up or more importantly rpm down?

 

23 - 24 mph/1000 rpm in 5th gear?
That's about a 1.15:1.00 ratio change from what it is now (20 mph/1000rpm)

 

Found this old thread whilst searching for info about lengthening the final drive for 308/328 to drop revs on the highway a bit. Has anyone ever succesfully done this by changing the drop gears?

I.

 

FYI here's the Michelotto kit for the use of variable ratio cascade gears sets. It comprised the clutch shaft, special cascade gear cover and the relative gears.
Homologated ratios are (ratio-gear teeths):
0.622 22,33,28,30
0.671 23,32,28,30
0.723 24,31,28,30
0.778 25,30,28,30
0.837 26,29,28,30
0.9 27,28,28,30
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How does any of that compare to standard - from what I've read these things'll give you a top end of between 100 & 160 (i.e. pretty much standard at the long end) which is all great for track work, but what I'm really after is taller gearing if it was possible.

Beside's, I read of price tags of many $1000s for the Michelotto kit. I wonder how much interest there would be in a kit that dropped the revs by 5-700 rpm in 5th?

1st is pretty short anyway & so while (in theory) doing this would affect acceleration I doubt that in reality it would be that much - you'd just need to alter the way you drive a bit. In my 328 I find I really don't even use second that much while on the move unless speeds are very low because, again, its just a bit short & really not necessary most of the time. I think that in some respects lengthening the gearing might , in reality, make the thing a bit quicker down the road. It should certainly make high speed, long distance travel less frenetic.

I.

 

The whole point of being able to change the cascade gear ratio is that you can do so in less than 20 minutes and be able to drive the car on track, road or mountain with the most appropriate ratio.
Don't forget that the Michelotto cars also used a gearbox with competition ratios (close ratio) so the combination of these factors makes the car much faster.
Group 4 and Group B 308 gear ratios are:
3.077 :1
2.313 :1
1.789 :1
1.409 :1
1.208 :1

 

Do you happen to know what the drop gear ratio is on the std 308 or 328?

I.

 

1.111:1 (30, 28, 27 number of gear teeth).

 

Thanks for that - so even the longest Michelotto gear is shorter than the standard setup. I'd like to go in the other direction if I could but sadly I suspect it'd be exhorbitantly expensive to do (even if it is just to get 3 cogs cut!)

rgds

Iain

 

Again the setup is 4 gears + clutch shaft + cover + bearings + (optional) additional gears to obtain other ratios.
Basic price is 5200€ for a complete kit + 2300€ per additional gear set.
When you think of the benefits, it completely transforms the car from an acceleration beast to a highway cruiser in minutes depending on the gearing used, I don't think it's so expensive.

Cheers.

 

Thanks, I understand that, but from what you have said the longest Michelotto gear is 0.9:1 & the standard drop gears are at 1.111:1. What I'm after is a set that delivered maybe 1.2:1 or even 1.25:1.

I wouldn't want to alter the gearbox or the diff - unless another (less expensive) way to achieve the same thing would be by altering the final drive ratio.

I.

 

It is perfectly feasible to make ANY ratio you want as long as you are using the 4 gears setup. With 3 gears the feasible ratios cannot vary more than +-10% compared to OEM due to obvious radius limitations (the gear radius cannot extend beyond the casing's inner border). With the 4 gear setup this limitation is much less restrictive and you can make ratios that vary by +-60% compared to OEM. They do not necessarily need to be FIA homologation compliant.

 

Ah, I see! I didn't realise you could have other ratios apart from the ones you mentioned before.

Am I right that the 5200 buys you just one setup & that then any additional ratios are an additional 2300. i.e. if you want 3 options you'd spend 9800 Euros?

Do you have any idea what the cost of a 3 gear setup would be that was say+10% (or as far as you could go making the gear taller)

Thanks for all the information - its interesting and useful.

rgds

Iain

 

The prices are correct. You would be having a total of 12 gears + 1 cover + 1 clutch shaft + bearings and ancillaries (circlips, pins, everything needed) for a total of 9800€. Not so expensive when you think of it.
The expense to make a +-10% 3 gear set would be around (I guess) 1800-2000€, too much for the percentage gained (again my opinion).

One thing you should always keep in mind is that this is no playfield. Anything wrong in the cascade gear set (the total engine torque is transmitted through it) and you're into an expensive repair (at best) or much much worse. Imagine the gears locking with you traveling at 100+mph....

 

Hey Stratos,

Happy New Year !

Why would it not just rip off the teaths ?

Morten

 

Happy 2008 to you and all.
What may happen is the middle gears axle's bearings are destroyed and it sits in a non-parallel axis as compared to top and bottom in which case it can just stuck.
Any issue with cascade gears can result to very severe damage to the bell housing and bell housings aren't particularly cheap.

How's your project progressing? The Michelotto car was recently sold

 

Ohh... I see

Do you know for what price the Michelotto car was sold ?

My project is on track. Most things are now considered and determined. Dismantling will start now. Aiming for turning the engine on within 10-11 months.

Morten