1996 Legacy Auto Trans fluid change advice.

[tedbull]

Hey Guys, I am doing a full service on my 1996 Legacy L wagon. My questions pretains to the automatic transmission. Most of my vehicles to date have been manual transmissions. This is my first auto trans service. I have read the procedure and its as simple as it gets, pull the plug, drain, add fresh. From what I gather it should take about 4 quarts to fill with just draining the pan and not messing with the torque converter.

 

My question is this: What fluid should I put in there? Stick with cheap fluid or go to something sythetic or "performance". The car has 132,000 miles on it. I purchased from the original owner but have no service paper work. I have put 45,000 on it since I bought it and have not done anything but oil changes untill just recently. I drained both front and rear diffs today and the fluid looked excellent and was not dirty or tinted at all. So, maybe the trans has been serviced as well??? 

 

But, either way. I want to start fresh. What is the best method here? What fluid to you recommend? Should I drain and add, then drive for a week and drain and add again to try and cycle as much old fluid out as possible. Should I consider pulling the pan and replaceing the filter screen while its on the lift?

 

To make this longer than necissary post longer. - The condition of this trans is basically good. It shifts a little hard at times but nothing anoying or concerning. the only thing it does do that stands out is this: At idle while stopped in gear the car will shutter when at a stop light. It shudders pretty damn hard. I own three subarus total and this is not the normal boxer rumble. It is not related to the CV axles like some will likely say. This is different. And when the trans is placed in neutral the shudder goes away completely. Place back in gear and its right back again. The shudder is significant. Been doing this since I bought it. It has not improved or become worse over 45,000 miles. Any ideas?

 

Thanks. Ted.

Edited May 7, 2014 by tedbull

[Fairtax4me]

You don't want to go synthetic with an old transmission.

Modern synthetic fluids may not play nice with the seals. It could do more harm than good.

 

Just stick with a regular Dexron III spec fluid. I use the Walmart Supertech Stuff and it works great.

 

The 4eat shifts a little hard anyway, especially when its cold since it seems to hold out the gears a little longer. Pretty normal.

 

As for the shudder, do both axles have the Subaru green cv joints? If not, probably the source of the shudder. Strange as it may sound, using aftermarket axles DOES make the car shudder.

Other than that, you'll want to make sure the maintenance is up to date, good plugs and wires, filters, PCV valve, and make sure there are no vacuum leaks, and the breather and PCV hoses are attached where they should be.

Run a half can of Seafoam in the intake to clean out intake and combustion chamber deposits and that will help smooth out the idle.

[tedbull]

You don't want to go synthetic with an old transmission.

Modern synthetic fluids may not play nice with the seals. It could do more harm than good.

 

Just stick with a regular Dexron III spec fluid. I use the Walmart Supertech Stuff and it works great.

 

The 4eat shifts a little hard anyway, especially when its cold since it seems to hold out the gears a little longer. Pretty normal.

 

As for the shudder, do both axles have the Subaru green cv joints? If not, probably the source of the shudder. Strange as it may sound, using aftermarket axles DOES make the car shudder.

Other than that, you'll want to make sure the maintenance is up to date, good plugs and wires, filters, PCV valve, and make sure there are no vacuum leaks, and the breather and PCV hoses are attached where they should be.

Run a half can of Seafoam in the intake to clean out intake and combustion chamber deposits and that will help smooth out the idle.

 

 

Alright, I will stick with the manufacturer recommended fluid.

 

The shudder was present when I purchased the vehicle with around 95,000 on it. The axles were all original I beleive. I replaced them with all aftermarket recently. This did not change the amount of the shudder at all. What gets me is that it completely goes away when shifting into neutral. That makes me think it is transmission related.

[Fairtax4me]

Transmissions don't shudder unless something is broken inside. Nothing inside the transmission is turning when the car is sitting still. All of the engines rotation is absorbed by the torque converter. So unless there's a clutch slipping in the trans, there is nothing moving to cause a shudder.

 

Two things happen when you put the trans in Nuetral.

1 it takes load off the engine. When the engine is under in gear at idle any roughness is amplified because the engine is trying to turn against the torque converter.

 

2 it takes load off of the drivetrain, mainly the front axles. Due to the way the auto transmission works, there is no transfer of motion to the rear wheels unless the front output shaft is turning. Front output shaft turns the front pinion gear, front diff and thus the front axles.

 

There is also stress on the engine and transmission mounts when in gear which is released when put into park/neutral so be sure to check those as well, though its not common for any of those to go bad.