Alloy bell housing question

[tower of strength]

ratios in the MT75 are as follows:

; 1st 2nd 3rd 4th 5th
2.0 16v;3.89, 2.08 ,1.34, 1.0, 0.82
2.3 16v;3.61, 2.08 ,1.44, 1.0, 0.82

there are some other ratios for the diesel and the later 2.3 16v. The gearbox concerned is from the 1995 onwards Scorpio, this has the starter on the drivers side and concentric,hydraulic clutch actuator.

I take it you chaps think I'll end up with bit of a pup, or are these ratios ok?

I need a fifth gear for the intended use (for economy and ear drum protection!!) on motorways. My sister lives oop north and my brother lives in Holland, I intend frequent trips to both in the car.

Mark

[msd1107]

Mark,

Here is a technical evaluation of the two gearbox ratios you referenced.

Assume an Elan with 155-13 tires, 3.77 differential, and 7000RPM.


The first MT75 ratios produce
Ratio...%diff Speed Diff
3.890..........31.4
.........87.0%.......27.3
2.080..........58.7
.........55.2%...... 32.4
1.340..........91.2
.........34.0%.......31.0
1.000.........122.2
.........22.0%.......26.8
0.820.........149.0
Figure of Merit -33.9
Speed difference increment -0.3

The Figure of Merit is a mathematical calculation as to how well the gear ratios are staged. It has a maximum value of 100. Well, what can we say, this is a sedan gearbox. First gear is virtually unusable in an Elan it is so low, the engine bogs when upshifting and overrevs when downshifting.

The second MT75 ratios produce
Ratio...%diff Speed Diff
3.610..........33.8
.........73.6%.......24.9
2.080..........58.7
.........44.4%...... 26.1
1.440..........84.8
.........44.0%.......37.3
1.000.........122.2
.........22.0%.......26.8
0.820.........149.0
Figure of Merit -409.2
Speed difference increment 1.7

First gear is marginally better, but the lower third gear really upsets the ratio progression..

Request a copy of the spreadsheet that generated these figures. It allows you to easily model any set of ratios, generates much more data than can be included here, and, in general, gives you more data than you ever thought you needed.

David
1968 36/7988
[email protected]

[tower of strength]

Hi David ,

thats very interesting, I'm not sure I can even start to understand the information though!!
I worked on 6500 rpm upshift, 165/80x13 tyres and a 3.77 diff, i had 1st pegged at 33mph(7 down on std), 2nd at 58mph (2 down on std),3rd at 83mph, (3down on std), 4th is the same and fifth will drop the rpm by 7-800 rpm. As a road car and based on my use of a 130/5 over 3 years, once moving, 1st isn't used, so realistically a standard Elan has a 3 speed box, mine'll have a 4speed!! I'll get better mpg, a wicked gear shift (its like a switch!!) and I'll hear my stereo on long runs whilst saving my engine and money!.
I realise the tall first in the Elan helps to give it some of its Zest, but in the real world (The "open Prison" built near Luton that is where I live) I dont think it will affect the overall experience.

I'm keeping the original set up, so If needed I'll be able to swap back!!

Can you explain the numbers and percentages and how they are worked out/what they actually mean?

regards

Mark