I put in 10w40 for 15 miles or so and only for flushing purposes. After that i poured in Honda MTF3. Gearbox was a 45614 (7 primary added later) in a low pressure turbo.It shifted very smooth and far more easy compared to before.
However if one of your synchros is bad maybe sticking with a little bit thicker mineral or a semisynthetic would help you getting into 2nd.
I suggest flushing with a 10w40 or 10w30, drive a couple of miles, if it does the trick, you either keep it in or try honda mtf3.

 

I like Honda MTF, I've used it in a few cars. It works as great as Redline MTL but it's cheaper. The problem with using engine oil these days is that it has friction modifiers in it which do not allow the synchros to operate properly.

 

A standard 10w-30 or 40 should do fine. I used to use Castrol GTX and I would change it out every oil change, it was easy and cheap enough.

 

I wouldn't use motor oil... those manuals were written many many years ago & now we all know how weak/fragile the trannies are & new trans oils are far superior. I have no clue how the OEM saab trans fluid for the newer cars compare.... I wouldn't try it

I never used Honda's fluid, always stuck with Redline's MTL which cured a few syncro issues & also pinion whinning in a few trannies. Great stuff & FAR superior to motor oil!!!

Being in the south you might want to try Redline's MT-90 which is a bit thicker & can take those 90++ degree days a lot easier.

There is also Redline's shockproof oil which is the best product for the C900 trannies. The boys at Scanwest swear by this fluid.......

MTL is much better then motor oil but it gets thin when the temp gets high. After eating up a few trannies with normal motor oil, synthetic motor oil, syncroshift, MTL & then MT-90 I kinda figured out what worked best for me. MT-90 worked a lot better in the summer & also when I did track days vs mtl & shockproof was a few steps better.

On my old SPG in 80 something degree weather only 10 or so minutes of driving at normal non aggressive speeds the oil temp would get well above 240 degrees causing my DIY oil cooler to kick in, couldn't imagine how hot it would get w/o a nice cooler & that was with a gallon of trans oil.

If it was me MT-90 or shockproof however I have read that people who have a lot of miles on a trans & they then switch to a synthetic fluid loose there trans. Other people have stated the opposite & get many years out of it.....

 

There is no doubt about MTL being better than motor oil. But most people don't have 300whp SPG's that get raced. I had 300k out of a well abused c900 trans.

 

FWIW my experimenting with trans oils was well before the car was in the 300+ hp area. Stock power levels to APC, FPR & exh upgrade.....

I already figured out how much better MT-90 was over MTL for summer months & due to Scanwest went the shockproof route. I would change MTL every fall.... put MT-90 in late spring & after a drivers school. Then switched to shockproof & Scanwest stated change it every 2+ years

 

There is no denying, that your tranny will give up the ghost from abuse, power, or just flat out "all of a sudden it decided to puke its guts" scenarios, WAAAY before it shits out because you used Walmart 10-30 instead of Honda MTF.

 

whats the opinion on using saab mtf0063?

 

if it resembles the consistency of some kind of oil, and you change it regularly, you can't go wrong.

 

My '85 900t 5 spd (246k) had 80w90 in it when I towed it home. I switched to 10w30 syn. Seems like alot of shrapnel on the drain plug when I changed it last and it jumps out of reverse under heavy throttle. I have no idea how many miles on the trans since the VIN indicates autotrans. I have 75w90 synthetic at work, should I try that? I remember reading somewhere that going from gear oil like Redline to motor oil causes rapid pinion bearing wear. Doesn't seem to a science backed kind of theory but we are talkin' C900's here. Years ago when I had my 89 900 the Redline MTL seemed to make it shift kind of notchy. This one seems to shift fine, just jumps occasionally.

 

reverse under heavy throttle.

:shock:

You sound like you like to have fun.

 

honda MTF is great, and its only 8$ a quart,, compared to 0063 saab fluid at 16$ a quart, thats a steal!

ive also had good luck with brad pen 80-90 gear oil. Just be warned that Gear oil shifts kinda tough when its cold, so thats a summer only fluid

 

No clue on the 0063 stufff, designed for the newer trannies not the old ones. Some 900/9-3 owners went from 0063 to redline mtl with great results.

You can get Redline MTL for $8-12 a bottle if I recall... or get a gallon jug of shockproof

synthetic motor oil is the worst thing you can put in these trannies..... way to slick for the syncro's

 

I'm in a similar boat of trying to extend the life of the trans for as long as possible before a full on rebuild. Running w/a basic 10-30 for a few miles and swapping in MTL, I'll update on any improvements/issues.

 

I like MTL also, have used it in my Jeeps. But the Redline site says NOT to use MTL, MT-85, or MT-90 in diffs with hypoid gears. So it probally shouldnt be used in the C900 tranny, right?
From the website..


ABOUT RED LINE GEAR OIL FOR MANUAL TRANSMISSIONS

Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement)
Red Line offers lubricants to pinpoint nearly every transmission application
MTL, MT-85 & MT-90 are not for use in differentials with hypoid gears
Excellent gear and synchro protection, balanced slipperiness for easier shifting in cold climates
Excellent for high- and low-mile transmissions
Compatible with petroleums and other synthetics

 

I have used MT-90 for at least 6 years in my trans. This trans has lasted me the longest. My car is roughly 250 whp. I however do not abuse my trans.