5EAT Ask your Questions!?!

I'm very interested in any more info on the final drive ratio swap. I have a guy here with a 5EAT BR9 (EDM) currently at around 330whp/350wtq on a billet 18G and meth. The car is very quick (like stg2 STi quick) through to the top of 3rd gear but 4th gear is a little disappointing. We were also looking at the Tribeca hypoid sets and learned a few things. Both the 3.083 and 3.583 gear sets use a 12T pinion so it may be possible to just swap the ring gears (even they're not sold separately). That makes swapping the gearing in the transmission much simpler as the front diff resides in the front casing which can be removed without stripping the whole trans down.

The Tribeca has the skinny, repackaged R160 rear diff with the filler and level plugs on the side of the main case, like ours. I'm not sure the old OXT hypoid set from '05, which has the full-size R160, will fit into the skinny case.

 

BTW, the BR9 ECU has tables defined for gear determination thresholds which it uses to calculate which gear the car is in based on engine speed vs. vehicle speed (which is sensed from the ABS system). It's easy to modify these thresholds by the amount by which the gear ratio differs, about 16%. That should keep the ECU happy. I have noticed on the CVT cars there are additional vehicle speed sensors for front and rear wheels, but these are absent on the 5EAT wiring diagrams. That makes me hopeful. I also could not find any sensor on the 5EAT for gear position, so I would think in that case the TCM is getting it's gear position data from the ECU (which we can modify). Frederik, is your ECU ID DEM5301C? I can tell you that the '11 Legacy 3.6R (DE5IB00G) has these tables present, even if they aren't defined in the '13 Outback 3.6R ROM. They are there for sure, just absent from the definition, and I've asked the Adept who made the definition to delve a little further.

 

The other reason we are looking at this is to reduce load on the transmission's clutch packs and planetary sets, which would allow us to further develop the torque output. I'm too scared to push it any further at this point, though the trans has an external cooler and has stood up to a lot of hard use so far.

Edited September 10, 2014 by fahr_side

i dont see how you could reuse the pinion and change rings to get a different gear ratio..

 

the pinion is the only thing that changes diameter and more importantly the pitch diameter.

 

both pinions maybe 12 tooth but they are not the same diameter.

 

typically ring and pinion are always matched .

 

the 5 eat has a front diff speed sensor inside the unit. and a rear speed sensor witch is external

 

the 5 eat gear position is taken from the shiftier inside the car as far as i know. and there are pressure pots in the trans mission to determine where there is pressure.

fahr_side, if you and your friend are able to get over this hurdle, I would be next up for the swap.

 

I'm holding off on trying it on my DD. I am working on slight improvements on the car and on the driver to get better track times for now.

 

Cheers!

Frank_ster, I know about the switch sensor in the shifter assembly. When the shifter is in D and can shift through all forward ranges, the ECU still wants to know which gear the trans is in so it can choose tables for things like per-gear timing compensation or per-gear boost target compensation etc. I think the TCM should have this data in real time but for some reason the ECU still has tables of parameters to calculate gear position from and you can log the calculated gear position from the ECU, which tells me it's using them.

 

Thanks for the info on the speed sensors. I thought they were CVT-only. I read up on this... the data is used by the TCM to control the center diff duty cycle. I don't think they necessarily are used to measure vehicle speed, just the speed difference between front and rear axles. Vehicle speed data is supplied by the ABS system.

the gear calcualtion is left over from the manual cars, the tcu knows what gear the trans is in.

but the tcu may not like the abs speed sensors reading differently from what the tcu thinks the vehicle speed is. but not sure.

the gear calcualtion is left over from the manual cars, the tcu knows what gear the trans is in.

Yes, I would have thought the TCM would work in a loop where the gear position was requested via the solenoids and confirmed in some way from the solenoids being in an energized state or not.

For an experiment I will try changing the thresholds 16% from stock and see who complains first, the ECU or TCM.

 

but the tcu may not like the abs speed sensors reading differently from what the tcu thinks the vehicle speed is. but not sure.

Thanks Frank_ster, I know you've done a lot of research on the TCM logic for your Megasquirt project. I'm much more familiar with the ECU logic so please bear with me if I have things wrong.

As I understand it the TCM parameter of front-rear wheel rotation ratio is used to calculate an appropriate duty cycle for the center diff.

It looks like the TCM is reading rear axle speed from the rear output shaft and front axle speed from the rear of the shaft that drives the pinion for the front diff. That would mean the TCM is measuring the rotational speed of the pinions to calculate this ratio, not the average speed of the wheels. I don't understand why Subaru does this instead of grabbing the data from the ABS system.

It does seem the TCM calculates a vehicle speed from the transmission sensor data but it's not clear if it compares that with the data from the ABS system. I don't see any error codes that reference those conditions in the transmission diagnostics. As you suggest it will probably trip an error code if it does compare. At least the wheels spinning slower than expected for a given engine speed and gear position should not cause a VDC intervention. The diagnostics for the TCM suggest the range for tolerance of the transmission vehicle speed sensor and that reported via SSM is 25 to 30%. There are codes for gear ratios being incorrect, from P0731 to P0736, which refer to issues with vehicle speed sensor, turbine (torque converter) speed sensor and gear shift clutches (slipping clutch packs). That suggests there isn't a comparison being done between TCM's calculation of vehicle speed and that from the ABS system, and that it only checks that rotational speed of the output shafts is commensurate with the torque converter turbine speed and gear position. Actually, based on the diagnostic steps for incorrect gear ratio codes I think this is how the TCM determines if the gear targeted has in fact been selected successfully. So it would seem both the ECU and the TCM have logic for this determination, though it's for different purposes. TCM is checking the transmission is functioning as commanded and the ECU is determining which gear is in play so it can select the appropriate table for per-gear compensations in timing, boost target etc.

 

If I'm right the TCM doesn't care if it's vehicle speed is correct or have any way of checking with the ABS system to see if it is. If I'm wrong.... I wonder if using the Tribeca or STi A-Line (also has 3.583 FD) TCM is necessary to work around this. I'll have a look around for some 'vacation photos' for guidance on compatibility.

 

EDIT: Yes, the Gear Determination Thresholds tables are there in the 3.6R ECU, and have the same values as the BR9.

Edited September 11, 2014 by fahr_side
Moar info

well the tcm will use the wheel sensors via abs contoller when the speed sensors in the trans mission are not working.

^ I was just about to write that. It is the safe mode fallback to maintain proper shifting speed.

Hmm. Does that mean that if the transmission output speed sensors are working the ABS data is ignored?

well maybe not ignored.. but not used for shifting...

 

my cars if i have them on the lift and run through the gears.. one of the front wheels stops turning the abs and sport light start flashing.

Yeah, they will do that as stock as well. Even on the dyno they throw a bitch fit if the front and rear wheels aren't in lock-step. Then you get CEL, ABS, cruise control... everything basically. Xmas.

fyi in the rom you can disable p0700 . so if you have a trans error the sport light will still flash but it wont set the cel and disable the cruise.

and the actual code of the problem will still be stored. so no real downside to doing this as far as i have seen.

^ Thanks, I'll bear that in mind!

Have a mouse chirp coming from what I believe is my transmission. Slightly increases with increased RPM's. Thoughts? It has shifted oddly the past 5-8k. Nothing really out of the ordinary, but I'm thinking it's the beginning of the end for the transmission. Filter change help possibly? Or flush? It was flushed 30k ago. 108k on the car.

^ drive shaft maybe ?

I'll take a closer look tomorrow when I can get her in the air. That's a possibility I considered, just sounds like its coming from too far up front and with the odd things the transmission does from time to time, I had it crossed off.

 

Thank you though.

is it normal for the ECU to pull timing when the shift lever is engaged during manual shift mode?

 

i'm seeing negative FKC increments (or, feedback knock correction), but no FLKC increments, and I think it's tied to when I press the shift lever, but I don't have a parameter to log to catch the shift lever engagement (I don't think). I'm shifting with full throttle. running the HexMods VB.

Does anyone actually know hexmods number?

i'm seeing negative FKC increments (or, feedback knock correction), but no FLKC increments

I just wanted to point out, in case I am confused as to what you're saying, that when it comes to knock control strategy, it's either or. In other words the car is either in FLKC mode or FBKC mode, but never both at the same time. There's many things that go into it but as a general understanding, from what I know is that FBKC is active on fast load changes, whereas FLKC is more granular and active when throttle changes are not large and sudden.

Here is what I sometimes see on my car. Knock sum goes up, and no FBKC registered. It is a situation, from what I understand, that the car thinks there was a knock event, but the situation did not call for a correction to timing.

Seeing pulled FLKC will never tell you if this is a new event or just learned FLKC.

Am I helping or just confusing you?

You are saying the car is actually showing pulled FBKC, that can be either real knock or noise.

In the tune itself, you can tune how much timing to pull, then the TCU tells the ECU it is about to shift. But this timing retard is not shown in FBKC or FLKC. So now it's a matter of looking into your FBKC, is it happening at high load or low load, how often, how much it is pulling etc.

I have had what has been deemed noise induced FBKC since I have owned this car.

Edited October 1, 2014 by fishbone

I'm seeing negative FBKC when WOT sometimes. It's not consistently at the same RPM but after looking at my logs it seems to be occurring in the few hundred RPM before RPMs drop, meaning I engaged a shift, whether that be mid range or high RPM. I don't see knock in any other driving condition.

 

The comment about FLKC was just to specify I am only seeing FBKC. I realize (only in the past few days, I've been reading) that they are separate and exclusive.

 

Your second to last sentence, starting with "In the tune itself...," answers my question.

 

I'm monitoring things closely now since I have a rebuilt engine. Trying to make sure it doesn't have to happen again...

I am by no means a tuning expert, but from what I have been told, if you see FBKC at WOT and high revs, it is likely that is not noise. Keep an eye on it.

Hey guys I just purchased a 05 lgt wagon 5eat, it drives fine and only 28k , and just for peace of mind , I wanted to do a tune up. All fluids and spark plugs hopefully sp will help my gas milage , meter reading 16.5 per gallon,

But to my question about changing my tranny fluid , from reading and local people have different opinions on how to do it, I bought and oil synthetic ATF , and Lucas 75-90 for diffs, is it ok just to drain and fill ? Is that all that's needed to do? Also wrong thread but since I'm here is it recommended to change my coil packs when changing spark plug ?

Hey guys I just purchased a 05 lgt wagon 5eat, it drives fine and only 28k , and just for peace of mind , I wanted to do a tune up. All fluids and spark plugs hopefully sp will help my gas milage , meter reading 16.5 per gallon,

But to my question about changing my tranny fluid , from reading and local people have different opinions on how to do it, I bought and oil synthetic ATF , and Lucas 75-90 for diffs, is it ok just to drain and fill ? Is that all that's needed to do? Also wrong thread but since I'm here is it recommended to change my coil packs when changing spark plug ?

 

Wow, 28k! That's a find! I guess "because Hawaii car"?

 

No, no need to change coil packs when doing plugs, unless you're getting misfires or something. As for mpg - city driving, you're probably not going to do much better than 16.5 mpg. With mods, worse. I'm getting around 12-13 in the city these days, but it's a LOT of acceleration and braking.

Cool no need coils , that saves me sum money for other stuff, I purchased it from a 96 year old guy 1 owner , actually his son sold it to me but yah didn't drive much so I was lucky it only had 27 k when I bought it, minor scrathes but everything else is sound so I really wanna take care of it:) n so drain and fill is good enough for tranny?

Heh guys , so this is my problem when im doing full gas acceleration my transmission kind of thinks before changing and it happens with 1-2 and 2-3 gear changes. It hits rev limiter and thinks for while and then changes. Car is 04 jdm lgt 5eat , any help ?