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

So I picked hp my second 4/4, a 2015 sigma engined model from a fellow TM member, and it's a wonderful car.

I noticed when I was cleaning the rebound spings and fitting new dampers that the original springs from factory were "Suplex", which I had thought was an upgrade.

On chatting to the previous owner, he suggested checking the diff, as he suspected it was an LSD. Lo and behold, it is a Limited Slip Differenetial.

On checking the build, no LSD is mentioned, previous owner thinks it may have been installed without him knowing and now seeing the Suplex suspension I wonder why Morgan would do this on what was to be a regular car.

Could it be they just were using what they had lying about, or maybe a cancelled order was changed to a new customer order and they just left the LSD and rebound springs in?

It handles great, so I just wondered if anyone would be able to shed some light on the parts.

Suplex lent some of their SSL springs and dampers with different rates to MMC for 'testing', apparently they were not seen again

I think I found 2

Now what about that diff....

Ran out of normal ones on chassis build day, or picked up the wrong one from the pallets behind after the tea break

A nice upgrade!

Hi Scotia Stev

My car is a 1999 4/4 with a Ford Zetec 1.8 engine. Some time ago I was trying to find what modern oil to use to replace the diff oil since the oils specified in the hand book are no longer available. I contacted a couple of dealers and the MMC for advice. One of these people, either a dealer or MMC themselves, I can't remember exactly who, told me that a number of 4/4's were fitted with LSD's by mistake because the axle manufacturer had incorrectly labelled them. As it turned out my car was not affected and has a standard ie none LSD axle

Regards Tony

I presume the diff oil is the same? Interesting and going to get the part number off it later today....

As it happens I will shortly be replacing my diff oil. As I understand it LSD,s require an additive a friction modifier that in the past needed to be added to normal diff oil separately by the person changing the oil. According to GoMog if this is not done it would result in serious damage to a LSD within 1000 miles. This was the reason I contacted the dealers and MMC to try to establish which diff I had and what oil to use. As it turns out the oil the dealer uses is Castrol Transmax limited slip 75W-140. This oil already contains the additive but can also be used in none LSD axles so that is what I will be using.

Regards Tony

Forgot to mention. According to a few videos on the internet the way to establish if you have an LSD is as follows. Jack the rear of the car clear of the ground (don't forget to chock the front wheels). With the hand brake off and the car in neutral rotate one of the back wheels. If the other back wheel rotates in the opposite direction you have a none LSD axle. If the other wheel rotates in the same direction it is an LSD.

Regards Tony

LSD additive is available from places like Demon Tweeks. My experience of not having enough additive after an oil change, was when reversing out of the garage, I had a chatter which sounded like a loose rear wheel. Amazingly a small volume of additive silences it completely. The chatter will be louder when turning. At low speed especially.