Lotus Elan and Lotus Elan Plus 2 Forums

Alan

Good question - its 71/2" with bolt on flanges and a Ford LSD.

On the last event I did I recall getting to around 30 - 35 before needing to change - and it came up very quickly.

What are the common diff ratios for a 7 1/2"

Thanks
Gavin

Sorry Gavin,
I just know what I have and what it does with an MT75, it suits a 180+BHP Zetec with 160 odd lb-ft torque and a 3:64 diff from a 2wd Scorpio which I believe is 7 1/2 same as yours. There's a big gap in the ratios between 1st and 2nd which is pretty common for modern gearboxes designed for normal non sporting road cars, my engines have enough power and more importantly torque to make this gap unimportant and the benefit is easier stop start traffic behaviour. Competition is a different thing and something I have no experience of, but I would have imagined that 1st was just needed to get you off the line for a hill climb?

Alan

I use my road car for the odd hill climb and sprint. In my case, the only difference between the road and competition is the speed with which things happen.

When I drop the clutch at an event, the engine picks up well and I find I need to change gear pretty much immediately - hence the frustation and thoughts about alternatives.
I reckon a first around 2.9 or 2.8 would suit me best.

I did run a ZF box for a while with a 4.1 diff which was absolutley perfect. My problem is that the box is destined for the other car.

I've just put the sprint on fuel injection which has absolutley transformed it. The truth is that I probably wont pull the engine out for a while now as it is running so well - so I guess I have a lot of time to cogitate the next improvement.

Cheers
Gavin

IIRC, 3.89 is the most common ratio Sierra, etc diff with 3.64 or 3.62 also available

gav wrote:Alan

Good question - its 71/2" with bolt on flanges and a Ford LSD.

On the last event I did I recall getting to around 30 - 35 before needing to change - and it came up very quickly.

What are the common diff ratios for a 7 1/2"

Thanks
Gavin

Thanks Peter

Whats the best way to check - 2 white marks and counting?

Cheers
Gavin

PeterK wrote:IIRC, 3.89 is the most common ratio Sierra, etc diff with 3.64 or 3.62 also available

gav wrote:Alan

Good question - its 71/2" with bolt on flanges and a Ford LSD.

On the last event I did I recall getting to around 30 - 35 before needing to change - and it came up very quickly.

What are the common diff ratios for a 7 1/2"

Thanks
Gavin

There is also a 3.38 that I have in a motorcycle engined Caterham 7 and I think an ultra rare 3.04 one although I may have dreamt that.

I'm still looking forward to getting my S2 back on the road in the next year.

I opted for the Voights conversion with a custom BGH gear set. Lots of choices there, but for my use, I wish a 0.75:1, 5-gear was available for high speed cruising. The 0.82 is better than the 1.00, but not as attractive as a 0.75. Traffic on interstates in my area moves at about 80 mph. My ratios are:

2.66
1.75
1.26
1.00
0.82

This gear set is almost exactly in between the close ratio and semi close ratio gear sets, but with a useable 5th gear extension. I will run a 3.55:1 rear end with a Quaife LSD and a big engine.

Anybody else have experience with a similar setup?

Bill

Hi Bill
My Plus 2S 130/5 runs with a 3.55 diff and 175/60 x 13 tyres.

The Lotus 5 speed box ratios are
1st 3.20
2nd 2.01
3rd 1.37
4th 1.00
5th 0.80

With the low profile small diameter tyres a higher first gear would be an advantage in some circumstances. However I have a very step driveway out from my house and it actually suits me to have the low first gear ratio to get up it especially on a cold morning with a cold engine. If my Plus 2 was more of a racer than a cruiser I would probably want a higher first gear like the close ratio 4 speed box in my Elan. The rest of the gears work fine in all circumstances for me in normal road use. In Australia the 0.8 overdrive is fine as we have rigorously enforced highway speed limits of a maximum of 110 km/h

cheers
Rohan

Hi Bill

Your wish for a 0.75 top ratio- possible but only if your AV box was originally in a 2.8 capri/sierra. if you swap the complete 5th cluster from a 1.6 sierra/capri to this box you'll get a 0.75 top.

John

the t5 gearboxes have ratios that suit the Elan
2.95 1.94 1.34 1.00 0.73 Also available with .8 and .63 5th gear

Dave Hughes

Dave

The ratios look ideal - but does the box fit a Spyder spaceframe chassis?

Thanks
Gavin

Hi.

Will this conversion fit in car with a replacement Lotus chassis? The car has a Zetec engine and the vac tank has been notched.
Keith

tablets32 wrote:Hi.

Will this conversion fit in car with a replacement Lotus chassis? The car has a Zetec engine and the vac tank has been notched.
Keith

Quite possibly, but best to ask Spyder http://www.spydercars.co.uk/

Hi Rohan.

The Lotus 5-speed ratios are a pretty close to the semi close ratio box but with a very useable 5th gear and are likely a good compromise for the +2 and your driving conditions.

Hi John.

I didn't know that was an option with the BGH gear set. How do I tell if my AV box was originally in a 2.8 capri/sierra?

What is unique about this particular version that allows the 0.75 top gear, when the others don't?

Hi Dave.

Those T5 ratios do look pretty good. To me the ratios are better than the semi close ratio box and include a high speed cruising 5th gear. This gear set seems particularly well suited to a heavier +2.

Bill

Hi Bill

Hope this helps- memory is wearing out!

Differences between the boxes- on a box fitted to a 2.8 engine car (Capri/XR4 etc) the input shaft differs. To fit it to the elan block the shaft has to be shortened (about .75 inches if I recall) and the forwardmost part of the splines has to be machined down (about .5 inches I think) to the shaft diameter. What you end up with is a shaft that has a shorter run of splines. If you were to put the two boxes together you'd notice the difference straight away. Other than that the boxes are dimensionally identical

As for the gearing differences, surprisingly the smaller engine Fords had the higher 5th ratio- o.82 as opposed to 0.825. Conversely if you were to fit a 5th cluster from a 2.8 box to a 1.6 one you'd end up with a lower 5th ratio.

On my own car 5th gives 24.9 mph/1000 revs- that's with std 155/80/13 tyres and a 3.5 diff. Before I swapped the cogs it used to give 22.7mph/1000 revs.

I'll see if I still have some pictures to show you the difference.

Regards

John