Lotus Elan

Differential gear ratios

PostPost by: promotor » Tue Jul 28, 2020 7:37 am

TBG wrote:If you speak to Gordon Strachan at NTG company in Arbroath he will do a 3:1 CWP for you. A very helpful chap indeed. https://www.ntgear.co.uk/ Good luck.


Did you ask him if he was one and the same Gordon Strachan? :D I bet he's been asked a thousand times, at least over the phone anyway!

Nice job persevering with this and finding an alternative to a 5 speed 'box!

Serious head on now! Did you use the backlash and depth of mesh settings recommended by NTG, or use the original English diff settings?
Did I read in your post somewhere that you deviated from the recommended settings?

The reason that I ask is that his first production run of 3.3 CWP's recommended 0.004" only whereas Ford specs are 0.005-0.007".
Also, are the depth of mesh settings (ie pinion shim adjustment) the same, or slightly offset against original Ford tooling?
Tighter backlash settings than factory spec bring the contact patch down towards the toe in a Ford diff (and should do in all hypoid gear sets). I wonder if this is how all his CWP's are, or whether the contact patch is still in the correct place with a tighter backlash?
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PostPost by: TBG » Tue Jul 28, 2020 8:18 am

Promotor - I did not do the actual work as I am not competent to deal with differential internals. I can take it out and put it back but the innards I leave to the more experienced!

When the CWP was delivered it came with instructions from Gordon and a photo of it showing how it should mesh when set up correctly. I assume my chum who did the work used these instructions.

Anyway I am thrilled to bits with the result and cannot wait for this blasted virus to bugger off and I can get back to chasing motorcycles in the Alps! :D
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PostPost by: TBG » Tue Jul 28, 2020 9:29 am

I have just spoken to Gordon at NTG and he has a dozen 3:1 cwps in stock as we speak. Be prepared for a slight whine on the over run. D
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PostPost by: gjz30075 » Tue Jul 28, 2020 4:29 pm

[quote="TBG"n stoc] Be prepared for a slight whine on the over run. D[/quote]

Is this Gordon's disclaimer, and expected?
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PostPost by: promotor » Tue Jul 28, 2020 5:07 pm

TBG wrote:Promotor - I did not do the actual work as I am not competent to deal with differential internals. I can take it out and put it back but the innards I leave to the more experienced!

When the CWP was delivered it came with instructions from Gordon and a photo of it showing how it should mesh when set up correctly. I assume my chum who did the work used these instructions.

Anyway I am thrilled to bits with the result and cannot wait for this blasted virus to bugger off and I can get back to chasing motorcycles in the Alps! :D


Thanks for the info! You might just slip past a few motorbikes on the twisties!

TBG wrote:I have just spoken to Gordon at NTG and he has a dozen 3:1 cwps in stock as we speak. Be prepared for a slight whine on the over run. D


I had heard this was the case previously on the 3.3 diffs unfortunately as I know someone who built a couple. As I understand it they were originally destined for race cars and not meant for quiet road cars.

Perhaps the option is to not let off the throttle/allow any overrun in the Alps!
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PostPost by: TBG » Tue Jul 28, 2020 5:13 pm

gizz375 - Well yes in away. I am not totally sure that my pinion shaft has been correctly tightened. The other thing is that Gordon makes these to a design and does not have failures as he uses amazing steel. Some he has seen he describes as made from chocolate. BUT he does not have the time and effort to do development work like the massive Ford lot had years ago. He has supplied a Lotus Cortina racer who got 60 racing miles from cwps made by the usual suspects - you know who they are! This chap has now done 600 racing miles without a problem.

The whine I get on the over run is hardly there and I cannot hear it unless I am going very slowly - so not often then! The noise is not damaging to the gears in any way. I am a very happy chappie as the drive is fantastic. :D
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PostPost by: Davidb » Tue Jul 28, 2020 8:02 pm

I had a whine on the overrun so I decided not take take the wife in the Elan any more...
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PostPost by: SENC » Wed Jul 29, 2020 12:25 am

Davidb wrote:I had a whine on the overrun so I decided not take take the wife in the Elan any more...


:lol: :lol:
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