Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 4/4 Limited Slip Diff Mystery

Friction modifier is used for limited slip differentials. No matter what you buy or who you buy it from, GM, Ford, BMW, it is all made, AFAIK, by a single world supplier, an Italian company by the name of Sturaco. Precisely the same stuff, and only the price changes from supplier to supplier..range of cost is 9 to 40 quid. In Canada I buy my BTR fluid from BMW who uses a very similar axle in their 3000 series. Their fluid comes with the additive. I stopped trusting oil/fluid companies when they all forgot to tell us when they stopped adding ZDDP.

Without getting too technical, non-LSDs don't need it..though it certainly won't hurt if you use it in one. As correctly noted, the infamous chatter begins if you forget in a LSD. It also lowers the fluid temperature by 5C+.IIRC, correctly Struaco became a BTR need in 1999 when they went to sintered cones in their axles..but that could merely be an cover for catch-up. BTR LSDs changed in 1999 and.issues were cured. The older BTRs are automatically cured when they are rebuilt as the rebuild kit overs it with the needed upgraded parts. I remember less of such issues with the non-LSD Morgan variant. Brian Gateson or Billy B. would know more.

Of course BTRs, like the Morgan Salisburys, are no longer made. But BTR parts are not a problem I understand By the way, BTR is better known as Dana Corporation or for some, Dana-Spicer [u]in our case their Australian division.[/u].Morgan decisions like this all have a curious history as in how do you put an heavy Australian pickup axle is in a hyper-light sports car! One would think a better choice would have been the world famous and nearby Quaife. Peter Morgan played with that near the end of the Salisbury era, the 12HA was a Salisbury with a great Quaife diff. But then Morgan management changed.

BTR fluid changes are called for every 50,000 miles. I change mine at 25k. I changed Salisbury fluid every 3000 miles.

Lorne

I use Millers, it ain't cheap but then neither is a failed Diff, plus with the low miles and stress in a light weight Mog you can leave it in for 3 or 4 years so ends up decent value

https://www.opieoils.co.uk/p-115249...ve-fully-synthetic-transmission-oil.aspx

I use the same as that used in Scoobies no problems modifiers or squeaks during my 24,000mls in ten years in the BTR, I'll probably change it this year at £19 for 2ltrs. There are a lot of Scoobies in the active rallying scene down here so that's why I chose this one

R380 gearbox will be done too with this once again quality and cost conscience.

I recall Richard Thorne saying most Morgan's are over serviced (when I bought my Green Plus 8) and he was right there, suspension and engine oil sure keep on it.

He was one of the agents that said if you like golf and death by food join MSCC so as he was the second one to say similar it will always be a no from me.

Like the cars it's a very personal choice.

Thanks for the heads up. It had fully synthetic 75 90 in it around 1k miles ago atv the dealer, sounds very quiet to me.

It definitely is an LSD, axle has MRA0031 on it as "Part number" and either 3:73:1 or 8:73:1 below.(must be 3:73:1)...

There is no money saving that justifies experimenting with a Morgan trad axle. Made-for-Morgan Salisbury axles and BTRs are no longer made. They have become very expensive or unobtainable. They are components the community will some day have to find a solution for.


BTR has been very specific since 1995/6 as to what these axles call for. I have been too afraid to take a risk since I bought my first one from them directly through Roger Shawyer in late 1999. And BTR and Castrol have kept changing the name of what should be used. Buying from BMW makes for a hassleless choice, regardless of the price. And that makes it available worldwide at any BMW dealer. After all the pain of their price is amortized over 25-50k miles. However, I am thrilled when anyone takes a risk I have no wish to entertain. I remember and miss Button very fondly for that . I still wait for his next email in my inbox

The original prescription was for a heavier fluid. a 140 version of 75 or 80w.. But think they made a mjstake and I am happy it is obliquely pointed out. BTR designed these axle for pickup trucks, IIRC the Ford Falcon Ute. Now the incredible Australian vehicle aftermarket makes billet versions! So that being said, the lighter stuff is smarter. Quaife also makes a MUCH better diff for a BTR and it is a bargain at 900 pounds. Morgan is a target market. Rover Plus 8, Roadsters and Aeros. After the swap they corner like they are on rails. Wow!

I have modified the Manual to recommend the lighter oil. Thank you

Lorne

P.S. Yes, the number you are seeing is a 3.73:1 BTR supplied Morgan with LSD final ratios options of 3.06, 3.23, 3.45 and 3.73. They could also be had with a 4.10 ratio on very special order. I took the advice of my UK dealer friends and chosde a 3:45. Dealers are all hooligans!

When we did the mechanical rebuild on Little Red a couple years ago, I installed a Quaife ATB limited slip. The car was factory equipped with a 4.56:1 gear set, which I kept. This required a spacer for the ring gear, which was readily available from Billy Bellinger. I contacted Quaife about oil, and they said that, while not necessary because the ATB is all gears and no clutches, the LSD additive increases lubricity and lowers temperature. I went with Redline 75W90 GL-5.

Morris Lubricants OE suppliers to Morgan do several specialised gear oils for LSD's, have a look at their website...

The Morris Diff oil is Mineral based as is the Comma I use and the same viscosity rating.

I used the same Redline 75W90 GL-5, which includes friction modifier, for my BTR cone type LSD axle. A lot easier than messing around with additives to old oil. It cured the clicking I got when maneovering on full lock with factory supplied oil. That was 25,000 miles ago. Recall having to buy another bottle as axle took more than volume quoted in handbook.

You may find that fairly quickly you will see issues with the limited slip diff fitted to Morgans when using the oil with the additive already in. Nothing wrong with Castrol Transmax, it's the oil of choice for me too and I think the best available! Just add some more LSD additive if/when you have any symptoms.