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4EAT binding problem gear ratio guru's


spacechiken
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Background, I am very mechanical, was a Nissan Master tech for years and have always owned Subarus so I am familiar with them for the most part. This is my first 4EAT car.

 

Kind of pulling my hair out on this one, here is a short history. I purchased the car with no transmission and a blown engine. Car is a 98 Legacy GT wagon automatic. I refreshed and installed a JDM EJ25D with automatic transmission (which is what the car was originally). I am getting a shuddering on acceleration even going in a straight line. I can hear the strain on the tires as they fight for grip and such and can tell the difference when I bring it from drive to first or second and it goes to 50/50 and gets worse. Tires are all pretty close, measured the circ. to be just outside the Subaru recommended tolerance. I am planning on buying new tires soon as well but this shouldn't be binding going straight like it is, I've even filled the tires to be the same diameter to eliminate that.

 

So I got underneath he car to check the rear diff and rest of the driveline. When I turn the rear diff the gear ratio comes out to be about 2.3:1 which from what I can tell is not a Subaru factory gear ratio. It does not look like it has ever been replaced (no marks on bolts, etc.) My question is since I am not very familiar with the 4EAT, does the center diff not have a 1:1 ratio but instead has a reduction to give the final drive of 4.44 like what is supposed to be in the car? I don't have another diff to physically measure the ratio output. The car drives great in FWD with the fuse in and once you get up to speed the center diff doesn't seem to bind anymore. I've been driving it with the fuse in just because I don't want to grenade the center diff if the gear ratios do indeed turn out to be way off.

 

The shudder and binding have gotten better with a few fluid changes and was almost completely gone one day so maybe the clutches are just sticking and need to be cleaned off? But it still wouldn't explain the binding going straight.

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^ there is a spot in the fuse box called "fwd" when you put this fuse in the car becomes totally fwd. try this ...

 

the out back has 4.44 ratio and legacy has 4.10 ratio if you changed the tranny and put in an outback tranny into a legacy you will have this problem.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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^ Read above, I've been driving in FWD with the fuse which is why I know the Duty C is working properly along with the fact that I can feel a physical change in the bind from drive to 1st and 2nd when the AWD goes from 90/10 to 50/50. Car drives great in FWD. The transmission I installed is the correct 4.44 gear ratio that I thought my car was equipped with. Where I ran into trouble is when I turned the diff, the ratio I got was closer to 2.3:1 which totally baffles me. Subaru didn't make that ratio that I know of, I know other vehicles use the R160 but I don't have a clue why anyone would install that ratio in this vehicles when it was pretty much stock when I bought it. Either something is really messed up with the diff or I was hallucinating when I was turning the shaft. Diff feels fine, no grinding or popping, a little more backlash tolerance than I think is supposed to be there but it shouldn't effect ratio. I'm going to put it up on all fours this weekend and see if the rear tires are indeed moving about 2:1 to the fronts and also recheck the ratio just to make sure my sleep deprivation wasn't getting the best of me.
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^ were the two back wheels turning together? if only one rear was turning you would get the results you speak of.

 

there is no center diff on the regular model of the 4 eat its front wheel drive wit a clutch pack sending power to rear wheels.. so when you accelerate it sends power to the rear once you maintain speed its pure fwd.

 

i'm sure your rear dff is 4.11 coupple months back some one pm'ed me with the exact same issues as you.

 

leacy 4.11 outback 4.44

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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My car should be 4.44 since it's originally a 4EAT GT, the 5 speeds had the 4.11 ratio. I didn't think of the open diff possibly throwing off the ratio with one tire spinning. I'll see if I can rotate both at the same time to get a better idea.

 

That's interesting about the AWD, I know the TCM uses the speed signal variance to help with power transfer to the rear when slipping and turning but on acceleration does it change it from a load signal or is it just a basic "x" amount of transfer per slope of the increasing MPH?

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^ 4 eat legacy is 4.11 4 eat outback 4.44 as far as i know.

 

so it looks like you put 4.44 tranny and front diff with the 4.11 rear diff.

 

 

not entirely sure how it does the math for the transfer clutch , it seems at higher throttle loads but once our up to speed its fwd.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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My car should be 4.44 since it's originally a 4EAT GT, the 5 speeds had the 4.11 ratio. I didn't think of the open diff possibly throwing off the ratio with one tire spinning. I'll see if I can rotate both at the same time to get a better idea.

 

That's interesting about the AWD, I know the TCM uses the speed signal variance to help with power transfer to the rear when slipping and turning but on acceleration does it change it from a load signal or is it just a basic "x" amount of transfer per slope of the increasing MPH?

 

definately if only 1 rear tire is turning is going to miltiply the ratio by exactly 2.

 

so leave one rear wheel on the ground count how many times you need to turn the driveshaft for the other rear tire to turn exactly twice.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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Checked the ratio today with one wheel blocked. I have the correct 4.44 in the rear so that eliminates that. Fluid was pretty much new when I drained it but installed new fluid anyway. The only thing that I can think of now are the tires which aren't terribly out of spec from each other. I'll be buying new tires in a couple weeks. Going to keep my eye out on some Michelin sales around black Friday. Going to throw in some lubegaurd for the time being, I saw a few threads where someone was claiming great results on multiple cars using it so might as well give it a try.

 

On another note, any Tampa people going to the rally cross event tomorrow?

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There is not a huge jump in the AWD ratio between 1 and 2 or any other gear, it's pretty subtle.

 

However, above a certain speed the TCU stops looking for a front/rear driveshaft speed mismatch which would indicate slippage and a need for more AWD lockup.

 

If the speed sensors think there's a mismatch it will apply a lot of AWD lockup at lower speeds, then release the amount at higher speeds.

 

Is the ATF Temp light flashing on startup?

Have you checked for TCU codes? There can be some error codes without the ATF temp light flashing.

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No at temp light flashing. No codes while driving in fwd. Sometimes in awd I will get a torque converter lockup code p750 I believe which is cause by the binding I am finding. Going through the trouble diagnostics everything checks out and one of the causes of the code could be mechanical influence.
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^ well you said the shuddering went away when you put in the fwd fuse? right?

 

um try this..

 

jack up both drivers side wheels

 

put a paint mark on each wheel ..

 

put a camera on them and put it into drive.

 

watch the video in slow motion and see what you get.

 

as far as the tcu keeping track of front and rear output speeds i dont feel that its realy doing that. itts active 4wd not reactive.

if you put on blocks and accelerate to 30 mph and maintain 30 mph the 4 eat cas i played with the rear wheels stop completely maintaining pretty much any speed.( the only one that would is a 4 eat vdc model that actually has a center differential. )

if you up on blocks and then accelerate and the rear wheels are not turning they will start again. and freewheel to a stop once you stop accelerating.

 

so for this test to work nicely you will probably will have to hold the brakes and give some throttle and maintain like 5 mph.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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The 4EAT adjusts the lockup (duty cycle of the solenoid signal) based on front/rear wheel speed variation up to 20mph or 30 mph or something like that on my '03, there is no question. I am pretty sure the gen before that behaves the same.

 

I had a dramatic example of this when I put an '04 trans in my '03 and for '04 they reversed the solenoid signal polarity.

 

On snow I would step on it and the fronts would spin alone until the fronts reached the magic speed, then when the TCU *stopped* calling for AWD based on the different wheel speeds the AWD would bang in.

 

(when the TCU called for more lockup, the trans responded by providing less)

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I won't have time to put it up on blocks until after thanksgiving because I'm working everyday until then maybe longer. I may have found some info though, I found one thread where a person with the same part number as me and he found that he has a 4.1 ratio transmission even though they are stated as 4.44

 

Can anyone look up a transmission ratio for a part number of a transmission? I am having trouble finding them. My transmission part number is TZ102Z1AAA-CC

 

If this transmission is a 4.11 as it turned out to be for this other guy that would be my problem. I may have a lead on a 4.11 diff if this is the case.

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Is that the new trans part#?

 

Do you have the # off the old trans?

 

If your eyes are good enough, you can see the ring and pinion looking down the dipstick tube. Of course you have to be abl;e to look and get light down there at the same time.

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That is the new part number. I bought the car without a transmission so I don't know the original. I do know the new part number is JDM specific and I'm having a hard time decoding it. The 7th digit is supposed to be the ratio. A 2 would be 4.44 and an A would be 4.11 from what I have found but I can't find anything on it being a 1 other than that guys thread where he said he found it was 4.11.

 

I can stick my scope Down the dipstick to see the front diff but I may have a hard time finding a good reference point to count revolutions.

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I'll try to check that tomorrow before I head to work. From what I'm finding I'm leaning towards it being a 4.11 so I'm going to get this diff coming, couldn't pass up the deal for an LSD. I think my scope is small enough to fit down the dipstick and it has a light on the end so as long as the gear fluid does get on the camera and blur it out I should be fine. I'm just surprised there isn't more information on these transmissions since most JDM importers are selling this very part number.
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  • 3 weeks later...
Update, after working for pretty much two weeks straight I finally got a day off today so I installed the wifes coil overs and threw the new 4.11 diff in. Fixed the problem entirely. So if anyone searches this transmission part number wondering what gear ration it is, it's definitely a 4.11 rather than the 4.44. From everything I read all second gen 2.5 auto's were supposed to have 4.44 transmissions. I wonder what model this came out of, it's a 1996 motorset so it has the hydraulic lifter heads.
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