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Motul Gear 300 in Rear Diff

8K views 9 replies 5 participants last post by  Acrdys 
#1 ·
I am getting 5 liters of Motul Gear 300 for my MT, which only requires 3.5 liters. So I will have atleast 1 liter left for the .8 required in the Rear Diff. Does anyone not recommend Gear 300 in the rear diff?
 
#2 ·
yeah i beleive is 3.8 for the tranny and just keep pouring in the rear diff until it starts spewing out :baaa:

I just did used motul gear 300 on my rear diff. Took it for a run and didn't feel a difference (duh) I just wanted to check leaks :)

Jacked the car back up and did my tranny. Feels awsome.

I ended up using 5 bottles and some left over.
 
#3 ·
Yeah, you should be fine with that. Go to the transmission sticky that you'll find in the maintenance forum, it'll tell you all the variations that people use. As for filling the diff, remove both plugs, let drain, then replace the bottom plug. Fill until it starts to come out the top plug hole.

For the tranny, get a funnel with a long flexible tube end. Fill as you go, but do not overfill too much. too much will cause it to foam, and that can bad for gear life.
 
#4 ·
Does anyone not recommend Gear 300 in the rear diff?
I don't recommend Motul 300 in the rear differential.

You will likely not need all the volume specified for the gearbox. You should add some, check level, add some more and so on until the level is correct. It is likely you will find that you are using less than 3,8L (or whatever is specified). Although overfilling is not a problem (the gearbox is vented and excess will spill out onto the ground) as you now know Motul 300 is not free.

Save it for the next gearbox fill instead, and use something else of the correct specification (see owner's manual) for the rear differential -- something inexpensive and readily available. This saves you money.
 
#6 · (Edited)
Now, maybe I'm a little off, but everyone here keeps saying the trans holds 3.8 Litres. Isn't it 3.8 quarts? Not to be a smarta$$, but there's a big difference....
3.8 Litres = 4.02 Quarts (slightly higher then 3.8 Quarts)
3.5 Litres = 3.69 Quarts (slightly less then 3.8 Quarts)
3.25 Litres = 3.43 Quarts (Much less then 3.8 Quarts)

Good place to purchase, offers quantity estimates

Am I incorrect? Just want to make sure that the true amount doesn't get lost in translation...Under or Overfilling isn't a good practice....
 
#7 ·
Am I incorrect?
Not in your location, no. I think you're correct.

I checked to see what a "quart" is -- turns out 3.5L is 3.1 Imperial QT or 3.8 US QT... The clearest measure is 3.5L but old habits die hard I suppose.

On the bright side, the dipstick will warn of under filling, over filling isn't a problem with the splash-type vented system as far as I can tell, and the rear differential takes care of itself in that the level is dictated by over filling anyway. You're correct in the observations as far as I can tell though, thanks.
 
#8 ·
Cool deal. I've always run that way (capacity wise) on all my Subarus. I just didn't want to accidentally convey the wrong information. I've learned that while Forums are a REAL good source, some people end up taking the wrong information as gospel, not knowing any better. It was more for clarification to the poster who was asking the ??, as you seem more then knowledgable! The only real difference (maintenance-wise) between the sti and wrx tranny I believe is the fuild type (spash trans as opposed to a helper pump) and capacity...There are many other different compoents in the operation of the 2, but I believe those are the 2 for maintenance...
 
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