5 replies to this topic

[Drawfiler]

I will have to replace my Eclat diff sooner or later and wondered about altering the ration to give me a better fuel economy and quieter top speed cruising, have any of you done this, while I accept that I will need to change/ recalbrate the speedo is there something I have missed.
Peter

[Dunc]

It's not easy to source a replacement crown wheel and pinion. The standard diffs are 4.1:1 and 3.73:1. If you already have a 3.73:1 then there is not much you can do. If you have a 4.1:1 you can get a 3.73 from Lotusbits and bolt it in.

The diff itself is a salisbury 7HA, which wasn't fitted to very many cars. The Morgan +8 used a full width version with a 3.53:1 ratio, which was shared with the one of the Scimitars (SE4b?) and the first 50 SE5A's, but given the Morgan guys can't find them nowdays as replacements for broken ones, you'd have more chance of finding diamonds in your back garden.

If you already have a 3.73 diff, you might want to look at your gearbox, but given yours is a special one, you might not be that keen on replacing the ZF. Do you know which box it is and if it is overdriven? The Getrag 265 produces a 0.82 overdrive on top, which is probably about right for the diff ratios.

It is possible (but expensive) to have a CW&P made with higher gearing, which is the route I am going down with a Morgan race team and salisbury specialist, but the batch is for 3.1:1 which I think is too long for the 4 cylinder cars. Given the difference between a 4.1 and a 3.73, I doubt you would like the end result with a 3.1:1 as the 4cylinder wasn't really blessed with torque.

I have to phone the guy and enquire as to how mine is progressing (it's been "almost there" for about 6 mnths) and I'll ask him which ratios he has made (I think he had others made for the track morgans) but I'm not sure.

You might want to determine what the top gear of your gearbox is and examine box options if you already have a 3.73:1 - it would be easier and cheaper.

best wishes

D

[USAndretti42]

Shouldn't this be in the gearbox section?

[Drawfiler]

I have had a look at my diff and it is a 4.1 so there is room for a change, the gearbox x is ZF, I do not wish to change that for the maxi based box so it looks like a chat with Lotubits is in order.
Thanks for the help
Peter

[Drawfiler]

It would seem that the ZF gearbox top gear is 1:1 so no overdrive effect whereas the Maxi box does. My diff is 4.1:1 so i think the 3.73:1 will help counteract this and stop over revving at high speed.
Peter

[Dunc]

Sounds like you have an easy bolt in starting point. Lotus bits sold me one last year to act as a basis for my new one, and it wasn't expensive. Worth speaking to them about a speedo also. Probably cheaper than getting your one recalibrated.