gearbox oil

just like to get some inputs on gearbox oil, if I use a Castrol SMX synthetic / Longlife gearbox oil 75w90 on a 308/328.

Liqui Molly full synthetic 75w90, any one with experience ?

will it be that different or harder to shift etc, I understand Motul Motylgear 75W90 - Technosynthese are highly recommended for "hard to shift" gearboxes.

 

I put in castrol SAF-XJ 75-140w with a small amount of red line additive and is working much smoother in cold conditions here in the UK

 

This has been often discussed on here. The problem is that the same gear oil is lubricating both the transmission and the differential. You need a small amount of limited slip modifier to prevent the rings in the differential from "graunching" in tight turns. But if you use too much, it becomes too slippery for the sychros in the transmission to work properly. As a result, you need a compromise so that both the tranny and the differential are happy.

What many of us do is use Red Line 75W90NS, which does not have the limited slip modifier, along with 1 quart of Red Line 75W90, which does have the hypoid modifiers. I've used that combination in an '84 Mondial QV that I owned, my former '78 308 GTS, and now in my '86 328 GTS. It has worked great in all three cars, and I know a bunch of other 3x8 folks using the same combination and we are all satisfied with performance.

 

+ 1
This combo is the best I've used.

 

I use AMSOIL 75-90 extreme pressure synthetic with an additive for the differential. Absolutely no shifting issues in my 86 328s. been in over 2 years now...

 

thanks for sharing guys, helps !

cheers
Johnny

 

Brian Crall has recommended Redline MTL manual transaxle lubricant. Isn't this easier than mixing and matching?

 

This was the response I received from the UK Redline rep when looking at options.....

Richard, thank you for your enquiry.

In the Ferrari transaxle the 75W90NS is recommended, the MTL is a lower viscosity than specified and a GL-4 rather than a GL-5.

The MTL contains a very slight amount of friction modifier, it is basically a non slippery fluid.
The Ferrari limited slip transaxle doesn’t typically require a friction modifier, as it doesn’t chatter when making a slow/tight turn.

So contrary to what you have read or been told, Red Line 75W-90NS would be the recommended fluid.

 

My experience is the opposite. Without friction modifier it does chatter when making a slow/tight turn.

 

+1 this is the stuff. GL4 for 308/328 boxes. GL5 for most everything else.

 

So then what is the correct combination?

One quart of MTL into the 75W90NS base?

One quart of 75W90 into the MTL base?

MTL in lieu of anything else?

 

I just switched to 75W90NS at last annual service three weeks ago and the 2nd gear issue is GONE. From the first shift after startup there is absolutely no grinding. I am sold and will never use anything else.

 

ok, but are the protection still as good as non NS ?

 

I switched to :
What many of us do is use Red Line 75W90NS, which does not have the limited slip modifier, along with 1 quart of Red Line 75W90.
But I'm not sure the gearbox shifts as well as it did before. Trouble is I don't know what was in it before.
Has anyone found anything better than this combo?

 

Read post #3

 

My experience is same as Bolex - the Redline 75W90NS solved the difficulty of shifting into 2nd gear when cold.

 

Yes but does it introduce another problem, as mentioned above, diff chatter, which is a low "groan" when turning a tight corner under power? Without any friction modifier this might happen.

 

I switched my 308 QV to the Redline 3x75W90/1x75W90NS mix when I bought it 2.5 years ago; then this year switched to the Redline MTL (with Redline friction modifier) on Brian's recommendations - there are no hypoid gears in the 308 transaxle, so it doesn't need GL5 at all. While the Redline mix improved the cold second gear shifting, it's even better with MTL.

 

I've tried the MTL and the 75/90 & 75/90NS combination. The latter just feels better in my car so that's what I use. The 75W90 goes in first, then the NS.

If I recall Brian's advice was to use the MTL as a next step only if the 75/90 combination didn't feel/work right

 

I have never not used MTL in my own and a number of other 308/328's I service. I use it in all them now.

75/90 is very good too but the shift quality with MTL is better. MT90 is a good choice too.

One client had about 130,000 miles using it. I serviced the car since new and never saw the inside of the transmission. The motor was very tired, the whole car was getting tired but the trans worked like new. That car alone has convinced me it is a good choice for that transmission type. We had the motor out to replace head gaskets and getting into the trans never even crossed our minds.

 

So just to be perfectly clear, just use 100% Red Line MTL Transmission Gear Oil and nothing else, straight up. No mixing etc.

 

Thats an unusual mix though, the more usual is the other way round, 3x75W90NS/1x75W90 just to give enough friction modifier for the diff.

 

That is what I use.

 

Thanks!

 

Good info. I'll try switching to Redline MTL on the next gearbox oil change. Not that I've had any issues with the gearbox in the 4 years I've owned the car. Last year I put in Royal Purple, which the car seems to like just fine (6000+ miles this year).

BTW: What's the usual cadence for the gearbox oil changes? Annual, semi-annual, every 3-5 years?