what weight of synthetic gear oil/transmission fluid/ engine oil?

[IndyBlk5.0]

plan on changing my gear oil and gasket, going fresh on everything, might as well... so i need to know what weight of synthetic gear oil, then what type of synthetic transmission fluid? And im going with a fresh shortblock and heads with valve job and port, but using same pistons/crank/rods. but new bearings and rings. What weight of synthetic oil should i run?

 

[90mustangGT]

Synthetics tend to run thinner than dino oils, so running a little heavier will yield the same, but synthetics don't need the extra weight. So for the rear, 70W80 or 80W90 will work fine. For the tranny, synthetic ATF. I have mobile 1 5W30 in mine, and have had it in there for over a year now after a tranny builder said to go with this. I asked him about using Mobile 1 synthetic ATF and he said that might be better. For the engine, I run Mobil 5W30 Synthetic and also have an oil cooler. Remember the first number is the cold viscostity number the second is when it is warm. 5W30 and 10W30 flow the same once at operating temps, but 5W30 will get there faster on cold startups.

 

[HISSIN50]

i agree with 90GT.
for the motor oil: unless your engine guy says to do it, let the motor bed in before using synthetics in there. dont want to glaze the walls, etc. (i know you probably knew that, but just in case).

for the trans, i run Redline D4.
rear, like 90 said. your choice of what flavor. i like Redline and Royal Purple. anyone use Mobil 1 synthetic gear oil in the pumpkin? curious as to how you like it. i can only get 75/85 (think that was it) here, and i wanted something thicker last time i did it.

BTW, good idea on freshening fluids. i try to get friends to do it and they are too lazy or cheap. gives good piece of mind and improves wear characteristics for not much money. just me.

 

[IndyBlk5.0]

great info guys, i wasnt planning on running synthetic until i change my oil a few times, first at 100 miles, the again at 350 miles. then synthetic... still would like a more rock solid answer on what sny tranny fluid to use on a stock borg warner t5 with a spec stage 1 in front, thanks!

 

[IndyBlk5.0]

and how do you like your b303 cam 90mustanggt?

 

[87gtconv]

For the Rear Axle Oil I would use Red Line 75W90 and it takes about 3 quarts if you use the the 4 oz bottle of friction modifier. Engine oil either 5W30 where it is cold or my favorite weight 10W40 of course Red Line and 5 quarts is a fill. The T-5 fluid I recommend is Red Line D4 ATF and it should take about 3 quarts before it starts to dribble out the inspection hole!

 

[IndyBlk5.0]

is there a seal where the driveshaft connects to the differientials, if so, how hard is that seal to replace? i think it is leaking... Thank you...

 

[CobraWannabe]

I heard Mobil 1 is dino and not truely synthetic. Is this true? And when are oil changes due with dinos and synthetics?

 

[HISSIN50]

for motor oils, i personally dont use an extended OCI for the cars that use them. hydrocarbons and other contaminates still get in the oil. some (especially diesel owners) use an extended OCI. they also generally have oil analysis done to see how things are inside the motor.

as far as i know, M1 is one of the relatively few real synthetics. Castrol, etc are supposed to have a dino base stock.

indy, do you have all wheel drive? if not, i think you have one differential. there are seals on each axle (behind the brakes) and one on the snub (where the driveshaft meets the pumpkin).

 

[IndyBlk5.0]

yes, i am wondering how hard it will be to replace the seal where the driveshaft meets the "pumpkin" lol, excuse me if i dont know the lingo yet... (still trying to figure out how i got red fluid on the back of one of my flowmaster brackets... weird) I will check it out better later...