How do drop gears work in L140 Graziano

Hi all,

I have tried and tried to understand the nature of the ratios in the final gearing gearing and tried to create a calculator tied to the final drive and numbers, but it is very confusing and I cannot seem to find a calculator detailing out the steps.


It seems that the ratios are calculated as follows:

Effective...... to transfer gear Actual (i.e. 'with use of default transfer gear of 1.32)
1-4.37................. 1-3.311
2-2.71................. 2-2.053
3-1.93................. 3-1.462
4-1.50................. 4-1.136
5-1.24.................. 5-.939
6-1.04.................. 6-.788

But is there another gearing ratio change being a Final drive of 1-3.08?? It was mentioned somewhere but I cant seem to get this figured out.

How is the actual Gearing by gear calculated: Effective to transfer to final. Is there a calculator somwhere with each part of the gearing process?

The diameter of the rear tires on the GT-40 I will be using are 705.5mm diameter. 15 x 295/55 so I am wondering if you could help by pointing me at a calculator, or spreadsheet that allows the conversion of the L140 box to real speeds using the drop gear and final gearing ratios as I appear to missing something pretty basic in my understanding.

Thanks in advance to all,
Andrew
 
Hi Randy, Thanks for that. But it appears that the red links have nothing in them. And Im really trying to understand the relationship between the gearing, the drop gear and the final drive ratio, then converted to Tires used. but appreciated the link. thanks.
 

Randy Folsom

Supporter
Hi Randy, Thanks for that. But it appears that the red links have nothing in them. And Im really trying to understand the relationship between the gearing, the drop gear and the final drive ratio, then converted to Tires used. but appreciated the link. thanks.
Not sure what you mean by ‘red links’
 

Markus

SPRF40
Lifetime Supporter
Randy,
Andrew refers to the link you postet to the Dragtimes.com website.
The Red links should load "preset saved cars" but this does not work....

Screenshot_20240828_194253_Samsung Internet.jpg
 
Hi Randy, yes, you are correct. If you enter numbers into the fields and hit calculate, it generates results. If you click on any of the "saved" vehicles, it enters nothing into the fields. The issue I have is getting an understanding of how the Gallardo gearboxes hang together in terms of the gearing ratios. From initial Gear, through transfer gear to final drive. Once I understand this then I will have appropriate rations to enter. I just need someone with gearing knowledge to help talk me through the gearing configuration and how that box type works. Thanks Randy.
 
Hi Randy, Yes I have, and have reached out to John. But no response as yet. He mentions the ratios, and gives examples, but when reverse engineering for a calculator, the numbers don work and I think it may be tire sizing, but cant be sure.
 

Brian Kissel

Staff member
Admin
Lifetime Supporter
You might want to reach out to John directly through HGF. They did not want to be a forum supporter.

Regards Brian
 
HCF seem to have a few images on their site.



rs=w:2560


rs=w:600,h:300,cg:true


There seems to be a set of gears that transfer power from the output shaft to the rear differential pinion shaft.
then there is another set of gears that transfer power from the output shaft to the forward dive shaft. I'm not sure how the power/torque is split between the two axles.
Changing these 4 gears would alter the ratio of every gear on the input/output main shafts. Acting like a change in final drive ratio.
 
Yes, that seems to be correct, and this is the understanding of just how these gears interact to product correct final drive values. :)
 
This would be the main plate. The three gears visible above the plate are 3 of the 4 transfer/drop gears. the two lower ones are for the rear differential and the single smaller one the end of the shaft is for transferring the drive to the front differential propeller shaft. The splined shaft sticking up without the gear on it is the input shaft. there would be an extension shaft that slides over this that takes the drive from the clutch in the bell housing.

At least that is my take on it.
rs=w:2560,h:1282
 
Thanks everyone for the input. Yes, this appears to be correct.

In a nutshell what I'm trying to achieve is something like a formula (i.e. Gear ratio 1st = 3.311, transfer gear (i.e. normally 1.32 but is replaced by drop gear??? Is this correct??) = eg. 1.04, Final Gear Ratio = 3.08. Formula for gearing ratio = (3.311/1.04)/3.08)??? Is this correct?? = final gearing ratio for 1st gear.

Then for speed calc = RPM x ratio x Circumference and convert to Klm-mph/hr. Is this correct??

Basically just need to get toa formula and the nature of if the drop gear is a replacement for the transfer gear... which I think it is. Just need confirmation. And if the rest of the formula makes sense.

Once done, I will share on this forum for all else to use. :-)
 
just using this for referance.

states final drive is 3.59.
standard drop gear ratios = 1.32

3.59/1.32 = ~2.72

x new drop gear ratio of 1.04 => 2.72x1.04 => 2.83 final drive ratio?

There was a gear box calculator here posted by Chris in post #75.

you might be able to play around with the figures and get some shift points out of it or wheel speeds and see if you can get it to match up with the graphs and data posted by hcf at the bottom of this page


below is the factory ratios. So you would need to work out what

1ck2k36ra_794282.jpg
 
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