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Redline oil in the trans + diff


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Well with the cold weather and increased difficulty getting into gear quickly, I decided to put the redline oil I bought a few months ago in my daily driver RX. I did 75W90ns for the transmission and 75w90 for the LSD. The results are in...

 

It is probably the best 'mod' I have done to this RX so far. It feels like driving a brand new car! I have this in my other RX, but since I only drove it during summer months and never that often, I never truly appreciated it.

 

At 20 degrees outside and on a cold start, it shifts better than it did when warm on the old oil that was in it. There is virtually no difference between hot and cold, just super quick syncro and butter smooth shifts. Also it might be just me but it seems to pick up speed faster rolling down my sloped driveway (concrete) now when it's cold.

 

I was getting 28 on this car with 50/50 highway-city and babying it, and this last tank I got 25.5 with all city and not keeping out of the boost. I'll see what difference if any this oil makes on the next tank and report back. Anyway I feel comfortable saying this is the best $60 or so I've spent on the car so far.

 

The RX is now 100 times more enjoyable! All I can say is DO IT!

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I have been recomending Red line fluids for a long time now.

glad to hear somone who agrees.

the MTL might be feel evin smoother than the 75w90.

my wagon has the 75w90 in it and still is stiff cold.

my old RX (junkies) would consistantly grind 2nd gear when I got it. I changed it to MTL and within a week it was shifting smooth.

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I saw a lot of recommends for the MTL on nasioc and a few here as well. I almost got it but then decided to get the 75w90ns becuase it was GL-5 instead of GL-4, which is what you are supposed to use in a trans with internal hypoid diff. Conversely, most GL-5 spec'd oils also wear syncros faster, which may be why so many of these cars with high mileage develop shifting problems. I think a GL-4 like MTL would almost certianly provide at least some better shifting quality, but how much so, and at what long term effect on the differential I am not sure.

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I can report a very similar experience with redline 75w90NS in my manual tranny, 88 SPFI, 175k miles.

 

There is no comparison to shifting now than before I put it in. I can actually shift now (especially when cold)!

 

However.... I may have waited too long... I need to double clutch on downshifts otherwise it won't shift that well...

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what is a hypoid diff... i never understood that.

 

Hypoid is the way modern differential gears are cut. You see that the gears teeth are 'curved' and also that the driving gear (pinion) is located to mesh above or below the center line of the driven (crown wheel) gear.

 

In the olden days, bevel cut gears were used, which you may be familiar with, from cheap lawnmower steering boxes, technic legos, etc. They make contact exactly on thier centerlines at right angles. This means that the driveshaft had to be mounted higher, and the gears are noisier.

 

Hypoids are quieter because of thier nature, they have a sliding, more gradual contact pattern. Thats all well and good, but it makes the contact pressure higher, so a higher pressure rated oil is needed. Regular helical, bevel, and spur cut gears do not need the high pressure, GL-5 rated oils.

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A standard interval would be 60k (30k extreme service), and I would suggest keeping that if the car is subject to any abnormal abuse. Since manual transmissions are not subject to any filtering, and only have a magnet to collect metal particles, a full flush is the only way to really clean the system. Under normal daily operation, I would say 100k would not be a problem. In fact many people probably have run regular dino oil out past 100k in many of these older cars.

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  • 2 weeks later...

can this stuff make much difference in a perfectly running manual trans that doesnt' have any problems and has new synthetic gear oil in it...comments?

 

is this more a function of replacing old oil or a help for poorly shifting transmissions or something that even a perfectly running/shifting trans can gain benefit from? i always drain/fill with synthetics on my manual trans and have never noticed a lick of difference in anything.

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  • 2 weeks later...

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