Differential Lubricant

There are many threads where people have shared their experience of different gear oils. The oil manufacturers recommend prioritising synchros over diff, i.e. don't use products with slip agent added. I use Motul Gear 300 FWIW, but you'll get 5 or 6 different recommendations on here.

 

Redline 75W90NS

 

Like stated above - lots of recommendations - I like Mobil 1 Syn Gear Oil for this model

 

Another vote for Motul Gear 300 LS 75W90, where LS stands for "limited slip" differential. This is what I put in the transaxles of all of my Porsches/Ferraris.

 

Mobile 1 75W90 LS.

 

This is what I use, and I found a significant improvement over whatever the previous owner used.

 

This works great for me as well, and is what Redline themselves recommend. Better cold performance is especially noticeable.

The "NS" means it DOESN'T have any limited slip additive, which is important for the syncros.

IF you get limited slip chatter and it's bothersome, you can add a few ounces of limited slip additive (or mix 4 qts 75W90NS with 1 qt regular 75W90), but I have not found this to be necessary.

 

Just to be clear, I wasn't recommending the 300 LS, quite the opposite in fact. The LS version contains slip additive which is not good for your synchros.

 

With the 355 iron synchro..not an issue

With 360 430 problem

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Making the gear oil more slippery degrades the operation of the synchros no matter what they are made of.

 

That would show as hard shifting ..then yes try NS .. agreed

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Well, I stand corrected. It is a shame that Ferrari recommends a GL-5 oil when it has been reported on here over the years that a GL-4 oil should be used instead.

 

I've had great experiences with Red Line's 75W90 GL-5 Gear Oil.

 

You could always use what Ferrari recommends. Works great for me, the AMSOIL I had prior made the car almost undrivable, it was an awful experience. I can even shift second when cold. It's not butter but it shifts. No tooth chipping going in and out of gear either.


https://avepetroleum.com/uploads/prod_images/shell_spirax_s5_ate_75w-90_synthetic_transaxle_oil_pail.jpg


As I understand GL4's also work some say better since GL4 lubricant is designed for medium to low offset hypoid gears. In the 308, 328, 348, 355 transaxles there are NO hypoid gears of any type, hi, low, or medium, offset. Some say it works better lots of folks use it in the 308 world. Quite a few tech with decades experience recommend it. MTL and MT90 seem to be the one most people report positive effects from.

I'll probably try MTL when I use the 5 gallon pale of Spirax I have.

 

I was just going to post about S5 ATE.

 

I took @Rifledriver's advice (in a past thread) and used GL4 and my gearbox shifts great.

 

Since positraction is so common now most GL5 oils have it . You have to go out of your way to find a GL5 without. Chattering positraction is in most cases just an annoyance. I run both a 328 and a TR with no positraction additive and they chatter just a little so I just ignore it. I would much rather have the better shifting and better positraction lock up that goes with not using any additive.

 

MT-90?

 

My car with Redline 75w-90 shifts like butter. Makes me wonder what the fuss is all about .

 

MT-90 is what I put in mine quickly after finding out that the Motul Gear 300 LS did not work at all. It shifts much better now.

 

I use: Redline MT90 75w90 GL4

 

50/50 mix?

 

What do you mean? Mix with what?

 

Nevermind. I assumed you mixed Redline MT-90 with Redline 7w-90, but I see now you were simply referring to MT90. Could have just answered me with a “yes.”