Differential (5 articles)

Diff. reinforcement

One simple one on the Éclat is to fit a reinforcing strut between the two inner mounting points on the diff. This mod was carried out by Lotus for the Series 2 Elite/Eclat.

I didn't know about this - is it wise to do ? Is it an 'amateur' job or should you go to a dealer and get it done. I assume it supports the diff and lessens stress on the mounting points ?

Simple one is a piece of "U" section with a hole at either end. The distance between the holes may be found in the workshop manual, under chassis I think. The "u" section could be 20mm "legs" and a 30mm "across"

Well worth doing as is stiffens the back end

Amazing !

Trivia: Just read that our cars rear differential is a Salisbury unit from a Lansing Bagnall forklift truck. To the phonebook old boy! Find a supplier just for the fun of it

Diff. oil

A synthetic has the best properties. Recently, I've used the 75w90 synthetic (used to use Mobil 1, now AMSOIL). AMSOIL just announced their new 75w140 -- so my next top up will be with that, cuz I'm gonna put that in the diff.

The diff needs a 1/2" square socket - but you can do it with an open end wrench if the PO or some mechanic hasn't overtorqued the drain plug or the filler plug - open the filler first, before draining, to be sure you can refill it! Besides, it drains out better with an inlet for some air.

The tranny (if you have the Lotus/Maxi 5-speed) uses an allen wrench or hex tip (I use a torx bit on a socket drive). Filler is on right hand side of the gearbox. Try a T-40 bit. Be real sure you don't take a wrency to any of the cap nuts or bolts on the outside of the tranny - some are adjusters.

If you use a synthetic on the tranny, remember there are synchros, so you'll need something with a "Limited Slip" additive (like Redline with the "NS" suffix). Mobil 1 is too slippery. I'm going to try the new AMSOIL 75w140 stuff since that's got the lubricity *and* the limited-slip grip. (Don't ask me how the make the stuff slippery on the gears and sticky on the synchros. It's chemical magic.) One thing more... certain gear oils are better for "tall" gearboxes -- if the oil "climbs" the gears it is better... I don't know which ones -- I think the Redline does this. If the oil is too runny (thin) it won't climb out of the bath as well and the top parts won't get as much lubrication

Diff. Leak

Now that I've removed and stripped down the half shaft on The UFO, (Elite 501, 1976) the reason for the oil leak is apparent.

There is some damage to the shaft, right where the oil seal runs on it! This is right where the bearing fits against the shoulder of the shaft and is almost certainly due to a poor attempt to remove a bearing at some previous time. The oil seal runs very close to this shoulder.

Well, here is the fix I'm trying. I'm pretty sure I've found the cause of the damage and I can't see how it could get worse. So, making the oil seal run on an undamaged part of the shaft should fix things. The seal only needs to move 3mm outwards to take it clear, so the seal carrier/bearing clamp is at the engineering shop at present having a bit machined out, so the seal fits deeper into the carrier.

I *hope* to be able to confirm this fix soon, so I'm passing this info on in case it might be of general interest. In particular: realise that the oil seal runs *close* to the edge, so take great care when removing the bearing ... mentally write it off before you start, hammer it on the outer race to remove it, don't go near the shaft face.

Diff. replacement

There's oil in my drums and I need to do the dreaded diff seal replacement-a-thon. But I have a spare diff knocking about, that I got with the car, and I'm considering putting all my new seals, brake cylinders, shoes etc. on that, then just swapping it with the one on the car. The diff is an unknown quantity but it might save me having to take the car off the road for so long. So my question is this - are there any tests I can do to ascertain whether all is as it should be inside the diff, without having to stretch the casing, remove the cradle and gears and all that jazz? And, seals and driveshafts aside, how sturdy is the heart of the diff?


it's quite a bit of work however you do it. If you drop the diff, I strongly recommend you do a good rustproofing job on the chassis while you can get to it. Also rustproof *inside* the lateral box member while you are at it.

I think the diff itself is very sturdy. However, you won't be able to tell if it's noisy until it's in use. You should check that everything turns freely without 'cogging'; also check it with one output flange held still, though it may feel less smooth like this. Also check for severe backlash at the input flange - but don't be surprised if there is a fair bit.

Above all, check it's the right ratio! There should be a small plate somewhere giving the ratio.

Oh, another point - important! AFAIK, some diffs had breathers and some didn't. Those without ... guess what ... pressure can build up and force oil past the oil seals. So if one has a breather and t'other doesn't, it's an easy choice. If neither has a breather, you should consider fitting one.

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