formerGMguy

I'm about to change my diff/trans fluid and I'd like to get the project done before I hit the track this Sunday. I was doing some research and Redline seems to be highly recomended but I have no local source (1 million plus people in the Grand Rapids area, apparenly no one here needs good lube, go figure...). That said I'm considering the Mobil1 fluid, but I've yet to run across any specific info or reviews on Mobil1 75w-90. Anyone have good luck with the Mobil1, or is there anyone who's used both fluids?

bader$

I used it in a rear axle in a pickup truck and it did well. I have Lucas 75w90 in my 944S right now and it seem fine.

nickg

every car I used Redline in (and i always call them to get what is supposed to be used) has had the tranny fail after using Redline....i would not reccomend it. I use Lubromoly Vol synthese or Swepco only in the porsches....Vw gear oil is awesome stuff...but not cheap

Zero10

nickg, what fluid by Redline did you use?
If you were using their 75W90 I am shocked that you had more than 1 transmission fail. Of course, I don't know exactly what you mean by transmission failure.

As for the comparison, if you are sticking with 75W90 GL-4/5 gear oils, I would reccomend Amsoil MTG, that is their generic 75W90 gear oil, GL-5 rated but compatible with yellow metals. They have distributors everywhere.

I have heard many good things about the Mobil 1. It's viscosity is right in the middle of the range for 75W90 gear lubes (cst@40*C of 106, cst@100*C of 15.2), so it seems like a good oil for a normal-condition transmission. The Amsoil is a bit thinner which will make for easier shifting (especially when cold), but is probably more expensive.

For those of us with worn synchros, I am going to use Redline MTL (MUCH thinner than 75W90 gear lubes since it's a 75W80, but still carries GL-4 rating). I am hoping this will cure my notchy shifting problem. I will be swapping fluids next week sometime, and will report back with my results.

streckfu's

Swepco, baby.

nickg

i used Redline in VW's and a few other cars i had(porsche too) and without fail, all of them failed the tranny. I called Redline direct to get their reccommended oil for the specific application each time. All of the cars had no problems before and I changed the oil and withing 5 months it was humming with bearing noise. I used to sell Redline at a job and it happedned a lot to others with VW transaxles with relentless certainty.

OriginalSterm

i'm running motul right now. www.turbofrogperformance.com is where i buy it.

StoogeMoe

Zero, I don't think you will like Redline MTL. I tried that first in mine and it was slightly notchy. I switched to MT-90 and it is perfect.

____________________________________
1986 944 NA - Guards Red - 87k miles
1983 944 NA - Platinum metallic - awaiting new engine
1985.1 944 NA - Guards Red - donor car
1984 911 Carrera Coupe - Guards Red (gone, but not forgotten)
"If you're not living on the edge, you're not living"

35thSLP

Swepco here!

formerGMguy

Thanks for the replies guys. I think I'm going to go with zero10's advice and try the Mobil1. I'll make sure to leave a review for future use.

Zero10

Haha, I can give a completely neutral review and somebody says they will go with my advice

I've never heard a bad thing about using the Mobil 1 75W90 gear oil, but I haven't heard a lot of good things. It appears to be hard to find.
Do you have any shifting problems right now?

formerGMguy

I've got minor problems with the second gear synchros, plus some issues with the shift linkage that are unrelated.

Neutral reviews are the best "advice" in my opinion. I'd rather hear unbiased facts than personal feelings about how well something works.

Zero10

So far I have read about 100-150 reviews of various gear oils in RWD transaxles. From that I have found the general trend that the thinner the fluid is, the better shifting will be. There are exceptions for those in warmer climates, where it seems to have much less of an impact, and I even saw Amsoil Series 2000 75W90 referred to as making shifting easier (ha, ha, ha......), but it was from Florida where the temperatures don't get low enough to see it's ugly side.

What I draw from all of this is that you should get the thinnest fluid that still offers appropriate protection. Of course track cars require much more protection and therefore should run thicker fluids.

The mobil 1 75W90 seems to be at the thin end of 75W90 gear oils (the only thinner synthetic I found is Amsoil 75W90), so from my initial criteria it seems to be a good choice.

bgiere

FYI, this is the factory fill and recommended oil...it is NOT the same as the Mobil 1 at Autozone,etc...

http://www.lufteknic.com/Merchant2/m...ode=lubricants

Legoland951

I have used redline, mobil 1, and swepco on the track. I swear by redline. Never had any transmission failure other than mis-shifting while powershifting into 3rd on the track. Redline made worn out synchros shift better than swepco and mobil 1. In fact, the only failure I had was with swepco in my 85 4+3 speed manual transmission (corvette). The transmission blew up cracking the trans casing. I drive hard but I know how to shift as I am used to shifting WITHOUT using the clutch for either upshift or double clutch downshift other than 1st gear.