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  Topic Review (Newest First)
12-03-2012 04:25 PM
flstffxe Depending on what ratios you have in your 5mt this may be worth a read.
Changed my 5th gear ratio (manual, non-turbo) - NASIOC

Originally Posted by subeman90
So ever since I bought my Baja I have wished it turned fewer revs on the highway. Really I think the gas mileage is not that great either. I decided a long time ago I was going to do something about this someday. Well someday was finally last week Jan 5th 2012. Long story short I have a great friend that works at a Subaru dealer and he was nice enough to order me in some 5th gear sets for my Baja. In the picture below from left to right is a WRX .738, impreza .78, and Baja factory .85 5th gear sets. Part numbers are on the boxes in the pics if you are interested.

Here are a few pics of the inside of your manual transmission (5th gear is the one hanging off the end of the pic (sorry not my pic but borrowed from the net) and a pic of the case together with 5th gear exposed:

Now I am not going to sit here and tell you how to do this. Quite honestly I had a shop do it as I have no time for this nor can my car be down for an extended time frame. Here is what I can tell you. The transmission DOES NOT have to come out (unless you want to go that route) and those gears are kind of pressed on but a little heat and gentle love made mine come out. I had an independent Subaru mechanic do this for me and he charged me for 6 hours of labor. There were a few test drives in there and he was going into uncharted waters so I have no problem putting some extra $$$ in his pocket. In the end are the numbers that matter to us.

Here are my numbers: ( speed, revs old, revs new) I installed the .738 set
40 1800 1600
50 2300 1950
60 2800 2350
70 3350 2800
80 3800 3250
90 4250 3550
100 4850 4000

So with that being said I have no data for gas mileage. I filled the tank and parked it for the weekend and I really have no plans for any good highway trips for awhile.

here is a pic of a semi-legal speed with the new gears in it.

here are the links for 3 videos that were shot on the test track (#1 is before, #2 is after in the lower speeds, and #3 is after in the upper speeds)
Subaru Baja factory 5th gear - YouTube

Subaru Baja new 5th gear with .738 ratio (part 1) - YouTube

Subaru Baja new 5th gear .738 ratio (part 2) - YouTube
Look at this chart to get an idea of your 5th gear ratio.

IIRC most of the Forester NAs are a .780 and the XTs are a .738. However I have not dug through the chart to confirm. Just going off memory.

Subaru part number 32315AA420 is the .738 5th gear set. and can be had for just over $100. Labor is on you or your shop.
12-03-2012 11:00 AM
Duderotomy To expand on my previous post.

The gearing in the Outback and Legacy 6MT is barely an overdrive gear.
They both have a 6th gear ratio of 0.695 with a 4.111 or 4.444 final drive. The LGT has a 0.666 6th gear on a 4.111.
That will give you a marginal improvement in highway mileage, but compared to the Forester diesel's 0.557 6th gear ratio and 4.444 final drive it is minuscule.

Either way the 6th gear will improve fuel mileage. The split-case 6MT hasn't been proven to be any stronger or weaker than the outgoing 5MT as of yet.
If they throw the diesel's 6th gear in you'll get a true "overdrive" gear that will knock down your fuel consumption on the highway significantly. Subaru did this once before with the Legacy Spec.B
12-02-2012 08:39 AM
Duderotomy Hey guys, the 75mm 6MT that is coming in the new Forester is the same unit that comes in the Legacy, Outback, and diesel Forester.
The only version that will give the "overdrive " effect you're looking for is the diesel Forester versions. Every other iteration uses very similar 6th gear ratios to the normal 5th gear in previous gearboxes.
also, the 75mm 6mt is based on the 75mm 5mt. The STi gearbox is a completely different 85mm unit which uses larger diameter gears.

It has yet to be determined whether the 75mm 6mt is stronger than the 5mt. They're designed similarly using a split-case design, which isn't the strongest. The new gearbox has yet to be truly proven at higher power levels. The diesel has been a good test, amd the MY10 Legacy GT guys have only pushed as far as 400 lb-ft of torque. That specific LGT was sold off before they could conduct any durability tests on the gearbox.

I don't specifically know whether they retained the same gearbox length of the 5mt, but if they did then it will inherently be weaker than the 5mt since gears would have to be narrowed in order to fit everything into the transmission case.

Essentially though, if the gearbox still only has a 6th gear ratio of 0.7xx on a 4.111 final drive then it isn't going to be much more efficient on the highway than outgoing models. The extra gear allows them to space the other gears for better fuel economy.
12-01-2012 07:04 PM
The Sub No more than about 150lbs heavier than a comparable SH Forester...

Subaru 2013 Outback research webpage- specs, options, colors, photos, and more

My 2011 with its options is about 3340lbs...the Outback with similar features is about 3500. That is one passenger, not much. I am interested in this swap, but wonder about switching the AWD from MPT to center diff +, probably TCU, etc. Might be easier to just buy the car with the engine/trans you want......wait, that's no fun!! :P
12-01-2012 06:38 PM
twowings Isn't the Outback somewhat heavier than the Forester ?
12-01-2012 06:08 PM
Rand I've been driving a 2013 outback with the fb25 and the 6mt.

you dont use 6th until at least 70mph unless its totally flat terrain.
12-01-2012 04:16 PM
twowings I really believe this FB engine could pull a 6th overdrive gear fairly well until you got into the upper end of the weight rating...I've got great midrange passing and acceleration in 5th gear even pulling a 4x8 utility trailer loaded with furniture and 4 passengers...

I've started a '6-speed tranny fund' in anticipation...SubaruPartsGirl is on the case and when the parts inventory starts to build for 2014s I hope to put a swap together with someone who needs a 5-speed replacement....stay tuned !
11-13-2012 07:49 PM
Originally Posted by twowings View Post
Maybe the resident Subaru Parts person(s) here can find out about purchasing the tranny directly ??
Might not be avaible for a few months-year as Subaru's are selling like crazy, and spare engines and tranny's are in short supply. I was talking to a guy who got a fluke lemon 2012 impreza, and it took over 3 months for them to get a 5-speed tranny to replace his with (clutch came apart and destroyed most of the tranny)! And that was an "emergency need parts now" repair kind of thing, not a "I want to buy a 6-speed because race car!"

I agree however, the 6-speed in previous generations would be cool. Not sure about cost effectiveness, but eh, who cares!
11-13-2012 07:07 PM
twowings Maybe the resident Subaru Parts person(s) here can find out about purchasing the tranny directly ??
11-10-2012 09:00 AM
Lone Ranger I am liking this thread.
11-10-2012 05:34 AM
Originally Posted by Lone Ranger View Post
Does "light weight" mean weaker and easier to break [than the 5MT] under spirited use though? And would it bolt up to an EJ25?
Lightweight means it's not the hand built STi unit. It without a doubt is better than the 5MT in terms of strength. My guess is that it would bolt up the the Ej25, as the 2010-2012 Outback/Legacy had the 6-speed manual with the EJ, and now the FB engine with a 6-speed, and as far as I know, it's the same transmission.

And Dpm, is this actually the same one that is hooked up to the diesel engine? If so, then it probably would be a good choice to swap for a few WRX guys with 5-speeds.

Also, seeing as how the new FB and FA engines are very easy to turbocharge (even if they came N/A from the factory) I see aftermarket turbo set up getting more popular for N/A guys, and maybe even draw several people to buy the N/A with the 6-speed and turbo it....Hmmm....
11-09-2012 11:40 PM
dpm well it can handle the Diesel's torque...
11-09-2012 07:52 PM
Lone Ranger Does "light weight" mean weaker and easier to break [than the 5MT] under spirited use though? And would it bolt up to an EJ25?
11-09-2012 05:54 PM
Originally Posted by twowings View Post
Which 6-spd tranny Sti or Impreza would be a better all-round choice for someone wanting to cruise all-day at 65 mph/2100 rpm and have great mid-range power?
I'm not interested in stoplight-to-stoplight drag-racing prowess or top-end speed ....
The STi 6-speed would be a waste in a N/A Forester. The lightweight 6-speed that is coming in 2014 (and most likely, as already stated, is the same/similiar to the legacy/outback 6-speed manual) will be the best for fuel economy and quietness on the highway. The STi 6-speed would be faster than any other manual, but the lightweight 6-speed will probably be faster than the 5MT, and obviously better than the 4EAT or CVT.
11-09-2012 05:49 PM
twowings Which 6-spd tranny Sti or Impreza would be a better all-round choice for someone wanting to cruise all-day at 65 mph/2100 rpm and have great mid-range power?
I'm not interested in stoplight-to-stoplight drag-racing prowess or top-end speed ....
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