Lotus Elan

Wide-ratio 4 speed box: best solution or impossible dream?

PostPost by: Sea Ranch » Tue Jun 28, 2011 6:41 pm

With so much discussion of the merits and drawbacks of the 4 speed gearbox, 5 speed Lotus box and various alternate 5 speeds, I have noticed something missing: wide-ratio gear options for the 4 speed.

It seems to me that a lovely - perhaps the perfect - compromise between the wonderful shifting and durability of the four speed and the extended ratios and high speed cruising ability of the 5 speed variations would be to simply find alternate gears to make the original 4 speed "wider", including an overdrive 4th.

Obviously this would diminish the acceleration, but it would perhaps be the preferred compromise for those of us who no longer drive like "boy racers" and who need to use the car on highways. Another benefit would be no fitment issues.

Biggest question is: are there alternate gear sets out there, or would someone have to make them, or source them from other boxes, etc.?

Has this been discussed and rejected already? I haven't found any threads with this possibility covered. I remember seeing a discussion of someone wanting to manufacture a 5 speed set for the three rail 4 speed box (Australia?); persumably this did not get off the ground. And of course seems much more difficult that different ratios for the 4 speed.

Thoughts??

Randy
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PostPost by: garyeanderson » Tue Jun 28, 2011 7:09 pm

There is a bit of a gap between 2nd and 3rd on the wide box. Pleasse see attached spread sheet from David (MSD1107). If you had to use one, I would, I f don't then use a semi-close as a good all around compromise between a wide and the Ultra close. Many wide parts are serviceable in a semi or Ultra close box. Wide boxes are for parts!

Ford gear sets are available in a 3:36 2:01 1:40 1:1 (or very close to that) if you look for the gear set out of the 1971 Pinto that came with the 1600 Kent. This may be a bit more livable day to day if you wanted an alternate ratio that was lower.
Attachments
Davids tire diff and gearbox wide semi close.xls
David did this spread sheet a while back I plugged in the wide semi and ultra close. Tires and rpm are user set, alternate gears ratios can be substituted if you want.
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PostPost by: Elanintheforest » Tue Jun 28, 2011 7:28 pm

Randy, a lot of folks find that putting the 3.5:1 differential in the car provides just enough 'overdrive', whilst retaining that perfect 4 speed box. It's certainly still not a cruiser, but then it's not that sort of car!

I find that whilst an overdrive 5 speed box reduces the engine noise a little on a run, the wind noise around the side windows / door becomes exagerated to compensate...and I prefer the sound of webers to a wooosh of air!

Mark
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PostPost by: Ross Robbins » Tue Jun 28, 2011 7:55 pm

Randy,

I drove that sucker across Colorado and Utah on Interstate 70 at a steady 80+ MPH and it was very comfortable. Just over 4,000 RPM if I recall and it was no trouble or stress. I think I got almost 40 miles per gallon, too! Compared to a modern car where 30 to 40 MPH/thousand RPM is the norm it may seem busy but it was much more relaxed than my S2 Elan which does about 65 at the same RPM.
Don't worry just drive :evil: :evil:

Mark,
I would love to put a 3.55 in my S2 Elan and have been looking for quite a while. They seem to be as scarce as Rocking Horse S**t. Do you have a spare for sale???
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PostPost by: Elanintheforest » Tue Jun 28, 2011 8:21 pm

The 3.54 was fitted to one of the sport Escorts, Rod, I think it was the RS2000, and they come up on eBay quite often,

But the easiest way is to get a new crown wheel and pinion from Burtons:

http://www.burtonpower.com/parts-by-cat ... cwe35.html

Mark
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PostPost by: c42 » Tue Jun 28, 2011 9:24 pm

Mark

Thanks for that information, for some reason when I emailed Burtons last week they replied that they did not think that gear set would fit my +2; I guess the wrong guy answered my email!

Thanks again
John
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PostPost by: stugilmour » Wed Jun 29, 2011 12:23 am

c42 wrote:Mark

Thanks for that information, for some reason when I emailed Burtons last week they replied that they did not think that gear set would fit my +2; I guess the wrong guy answered my email!

Thanks again
John


John, although I did not purchase it from Burton, that is the configuration I put in my car. I got it from a seller on eBay UK, and he also had other parts available for the re-build, such as the gasket, crush thingy, bearings, etc. I had to get the output shaft seals separately; I think the RS2000 was a beam axle? and the seller didn't stock seals for Lotus. If you want to try the eBay route, "English axle" or "English diff" in the search box works pretty well to see what is available.

Not doubting Mark when he says the 3.54 diffs with the 11/39 C&P come up often in the UK, but in a year or two of looking I didn't find one where the seller would ship to NA, so the C&P and local re-build option worked better for me.

The sheet David did up (in piss-ant's post) is excellent. Randy, I was pretty nervous about the rev's, but got a lot more relaxed after adjusting the tach to read correctly. I put in the stock ratio's and my present tire profile/diameter in David's sheet and adjusted the tach to read correctly while matching to GPS speed readings in several gears to the sheet data. Of course it was all in the head, but with the tach reading correctly I could have sworn the car was quieter and more relaxed; all just needless anxiety. 8) I think my tach was out by about 600 rpm or so prior to adjustment. This is probably why when I first got the car I was holding to 5000 rpm and being passed by Greyhound buses. :)

I think when I did the math the change from 3.77 to 3.54 diff basically covered off the gearing change resulting from 78 or 80 profile stock tires to the 175/70/R13's I could get locally.
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PostPost by: Sea Ranch » Wed Jun 29, 2011 5:22 pm

Lots of great info and insights, as I have come to expect. Thanks to you all for the thoughts (and to Ross for his "Just drive it!" ethos!! I am, Ross. But planning for this winter, too :wink: ) Maybe I'm just too accustomed to the lower-revving, quieter contemporary cars, as you guys are saying. Hoping to take a 3 hour (one-way) trip in a couple weeks that involves freeway and highway/mountain driving so will get a good opportunity to "adjust" to higher revs and noise (will probably wear some ear plugs and really enjoy it :mrgreen: )

Couple questions:
It appears there are a fair number of ratios available, but is it possible to get more than 1:1 for fourth? If so, would that make the spread too wide? If you go to a 3.5 diff, does that make 1st gear just that much more difficult in traffic? I find with (presumably) a 3.7 diff that my present 1st is quite manageable, but with a 3.5??. Any good sources of 175/80 tires in North America?

Randy
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PostPost by: Higs » Wed Jun 29, 2011 7:05 pm

Randy

By its very nature, the 4 speed box has a 1:1 4th gear as all it does is join the input shaft from the engine to the prop shaft.

Different gear sets merely change the ratios of 1st, 2nd and 3rd gears.

Richard
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PostPost by: billwill » Thu Jun 30, 2011 1:25 am

>If you go to a 3.5 diff, does that make 1st gear just that much more difficult in traffic?

In a nutshell... NO.

I changed to a 3.54 diff around 19 years ago and have regularly driven summer & winter in London traffic without noticing any significant problems.
Bill Williams

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PostPost by: paddy » Sat Jul 02, 2011 7:34 am

Higs wrote:By its very nature, the 4 speed box has a 1:1 4th gear as all it does is join the input shaft from the engine to the prop shaft.

Different gear sets merely change the ratios of 1st, 2nd and 3rd gears.


Back in the 80s I read about a conversion where 3rd gear was converted to the overdrive, 1st and second spaced to suit. It got a reasonable write-up in a kit car magazine at the time.

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PostPost by: garyeanderson » Sat Jul 02, 2011 9:30 am

Ford in the U.S. did this with their top loader 4 speed and sold it in hundreds of thousands of pickups and vans, They called it a SROD or Single Rail OverDrive. A new input shaft was made with several more teeth to overdrive (heres the start of the problem) the second motion (counter) shaft which had several less teeth. All three indirect gears were overdriven. Ford made it so 3 gear came out as a 1:1 ratio and 4th was over driven .80 I think it was. So now the gearbox had 1 -> 2-> 4 ->3, where overdrive was where 3 was. The shift pattern was fixed to behave like a standard shift pattern by flipping one of the external shift linkage levers 180 degrees and pulling instead of pushing and vice versa. I had one in a F100 and it didn't live long, I ended up with second and third gears only and traded it in on for a F250 with a direct 4 and a creeper gear. If one had some tools, (lathe, Mill, welding equipment, etc you could do this too, but its easier to get a second job. The 4 speed that we have in the Elan works quite nicely if you don't need to be on a divided highway for extended periods, besides highways in an Elan are not a lot of fun anyways so take the surface roads and enjoy...
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PostPost by: Foxie » Sat Jul 02, 2011 6:54 pm

Elanintheforest wrote:The 3.54 was fitted to one of the sport Escorts, Rod, I think it was the RS2000, and they come up on eBay quite often,

But the easiest way is to get a new crown wheel and pinion from Burtons:
http://www.burtonpower.com/parts-by-cat ... cwe35.html
Mark


That's great, I've just ordered, been looking for one on E-Bay for the last two weeks :D

Did a practice and two races (Historic Class) in Mondello on the 19th. On the last corner of the slow down lap my old faithful diff chose to depart..... coasted in to the pits :mrgreen:
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PostPost by: JJDraper » Sat Jul 02, 2011 7:52 pm

You may not be searching for the right thing on ebay...

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 500wt_1156

As Mark said, they come up regularly. Even if it says all the bearings and seals are good, I would suggest getting it checked over by a specialist..

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PostPost by: Foxie » Sat Jul 02, 2011 8:09 pm

JJDraper wrote:You may not be searching for the right thing on ebay...
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 500wt_1156
As Mark said, they come up regularly. Even if it says all the bearings and seals are good, I would suggest getting it checked over by a specialist..


Thanks, I'm in now :D

You're probably right. I'm also the specialist :mrgreen:
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