Chaps, I have searched this forum top to bottom and I'm still unsure whether I should use 75W90NS or MTL in gearbox of my '93 348 spider (long overdue a fluid change, 3000 miles (approx 45,000 miles in total) a year including half a dozen trackdays). Opinion seems divided on these two products, so I was wondering what are the subjective differences, and what do other members of the brotherhood have installed? Many thanks. Stig
Okay, I can go with that and that is fine (and following your procedure) but is there any real opinion on GL4 spec oils as per Brian Call's post that keeps coming up when I search the forum? Thanks. As follows; ---------------------------------------------------------------------------------- My shop is right down the road from Redline and we use their products in the race cars. I have had many long conversations with them about their products and their recomendations. Ferrari specs GL5 gear oils for the transmissions. Due to Ferraris specs Redline will not officially suggest anything other than GL5 gear oils. GL5 basically means an oil that is designed for medium to high offset hypoid differentials. MTL is a GL4 lubricant which means it 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. I am not ordinarily an experimenter with others cars except in circumstances where the official way is obviously not working but I have seen MTL used with great success and zero problems in 308 transmissions since the product was introduced many years ago. It was also the oil of choice in the transaxles of the 355 and 348 Challenge race cars with zero problems. Those transmissions were subjected to greater stresses and heat in one weekend than most of our transmissions are in a lifetime. I cannot say that however of the AGIP oil spec'd by Ferrari at the time. One session at the track finished off several transaxles and we were told unofficially by Ferrari to quit using it in cars that would see track service. That garbage did remain the official oil. I have been using MTL in customer cars that had cronic shifting complaints for several years including one 85 308 in daily service with over 115,000 miles on it and the owner is pleased to this day how his transmission performs. It's great oil. If you have a shifting problem use it. I would not use it in any transaxle in a 275, 330, 365, BB, BBi, TR, 288, F40, 550, 456, 360, 430, 612, or 599. Those are all medium offset hypoid gear differentials and should have GL5 oil.
I believe it would still be preferred to use the 75w-90NS first, and if you do not get the desired results (poor shifting) then revert to the MTL. Most users are satisfied with 75w-90NS (I have been so far) and haven't felt the need to use MTL. But based on Brian's comments, the risk seems low if you went with MTL from the start, based on his experience with Challenge race cars, discussions with Redline, and customers street driven cars. I am considering using MTL on the next years change, as I still have difficulty going into 2nd gear when cold..I just skip to 3rd until it has been driven a couple miles.
I don't use the Redline Shockproof Ultra Light which would have given better shifting at cold. I use the regular Redline 75W90NS. My old italian friend Dominic adviced me not to use the Ultra Light because of the degeneration of protection when really hot as is here in Vegas. So, when cold I found just a little improvement, when hot is OK. I guess i got used to now and it feels good anyway.
Weird thing is that I have never experienced the legendary difficulties with 2nd gear in my 348 Spider or either of the 308s I owned in the past. My real worry is making sure that I have the best protection when hooning around at a trackday. It's not that I am super-tough on my tranny; I try to be smooth above all, but that said, Brian's post is pertaining to the rigours experienced by a track car (okay, "racing car", and I'd be flattering myself to say I was anyway near the abilities of a challenge racing driver). Does anyone have a perspective on 75w-90NS in a car used on the track?
