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Discussion Starter · #1 ·
Ok so im just putting in a new tranny onto my 8V T after the tranny lunched itself about a month back.....so the book says to put in str8 engine oil....is this correct? The tranny is from a 89T....
 

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normal oil will work but I ever had luck with motor oil. It's not made to take the abuse a trans throws at it...... to me motor oil should stay in the motor.

Lots of debate here..... redline MTL or Redline shockproof are by far the best oils I ever used with shockproof according to scanwest being the best (I sold my car with shockproof so I can't state how long the trans held together).

Others like honda's MTF.... a cheaper version of redline

synthetic motor oil is the worst thing for a trans
 

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run gear oil, whatever type is up to you

as stated, motor oil should stay in the motor, 25-30 years ago (when the owners manual was written) motor oil had alot more zinc, and other non EPA friendly additives that were better for gears. these were removed to help clean up emissions (motors that use oil, will burn cleaner)

gear oil still has all the right stuff in it
 

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My trans shaft seal leaked for 4 years and I put the heaviest stuff you can think of in. I actually just used the stop leak syrup think stuff for the last three years. No issues whatsoever and it is clean CLEAN in there.

I got the seal fixed and put like the thickest gear oil i could find in... I did use 10w 40 before that, but found the gear oil works best.
 

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Yeah, this is a heavily debatable subject. In the transmission my father rebuilt for my 91 SPG, I think we're going with RedLine. I've read and heard stories that are both for and against it, but I think that the horror stories probably come from people who are using the stuff in an older tranny that has more foundational issues than the fluid that's run inside of it.
 

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75-90 royal purple synthetic gear oil has been working in my 86 900-T exceptionally well. I would advise against using a higher weight gear oil in a C-900 trans as it will make it too hard to shift and wear the syncros too quickly. The shockproof would be a good oil, but I think it's too thick. Motor oil is not up to the task of a ring & pinion gear, and if used exclusively will break down and cause the transmission to fail.
 

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I would advise against using a higher weight gear oil in a C-900 trans as it will make it too hard to shift and wear the syncros too quickly. The shockproof would be a good oil, but I think it's too thick. Motor oil is not up to the task of a ring & pinion gear, and if used exclusively will break down and cause the transmission to fail.
I used motor oil for a long time until the trans seal leaked, then switched to the thickest stuff i could fine. The thick stuff seemed to shift very nicely. I have personally put over 100,000 on the car and the car has 326+ thousand on it with no tranny issues... ??

I realize that i could be very lucky and or just not be that hard on transmissions, but with no issues after that long, i wouldn't not recommend using thick gear oil.
 

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Discussion Starter · #13 ·
well the tranny goes back in this thurs/fri when I get back to CT to put it in i'll def be putting gear oil in it....
 

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75-90 royal purple synthetic gear oil has been working in my 86 900-T exceptionally well. I would advise against using a higher weight gear oil in a C-900 trans as it will make it too hard to shift and wear the syncros too quickly. The shockproof would be a good oil, but I think it's too thick. Motor oil is not up to the task of a ring & pinion gear, and if used exclusively will break down and cause the transmission to fail.
I thought synthetic was a big no no?
 

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I thought synthetic was a big no no?
meh, why would that be? Is this due to a suspicion of causing leaks? I would say that replacing the trans fluid in a 900 that has had the factory fill it's entire life may start leaks no matter what you put in there :lol: Mine does not leak on the synthetic and has quite a lot of miles on this fluid.

Trouble is really, we have a relatively conventional rear-drive style transmission, but it has a ring & pinion running in the same oil at the end of it to make it FWD. This makes any oil you want to use something of a compromise. There are likely several different gear oil products that will work equally well but I would always say you want a product intended to be used as a GEAR oil, not a motor oil, as motor oil was never intended to be used in a gear box.
 

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how about every one posts what they use and how many miles on the fluid?and results
 

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The "no synthetic oil in gear boxes" is an antiquated notion. Modern synthetics are fine as they do not have the same additives as older synthetics which as SAAB put it would damage the "yellow metals" in the gearbox.

When I first got the car and was obsessing about things I tried a few different gear oils and even a fancy "syncromesh fluid" from amsoil and quickly decided it was just a waste of money. I like to use 5w40 synthetic engine oil when available because it performs better while cold, and is the same thing I put in the engine - this adds a level of convenience in that you only have to keep one bottle of oil in the hatch to top up with if necessary. The synthetic also has better heat resistance than regular oil which is crucial. My odometer has never worked but it's been 3 years so maybe 40-50k miles and the trans is on all appearances in the same condition I received it in.
 
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