Transmission noise

[DaBlondDude]

New on the forum but I've been reading a lot of your stuff for a while now.

 

I bought a Subaru Legacy 2003 sedan, 2.5L automatic transmission, no turbo. I was losing oil and started to stall so I eliminated the obvious then suspected the head gasket. On my way to my friend's garage I blew through over two litres of oil, limped to his place/garage and when we dismounted it we found piston number four was missing a chunk, right on the lower edge, with no visible damage anywhere else (ÔÔ never even heard of this before). Needless to say I went looking for a motor.

 

I found a Legacy 2003 2.5: Automatic transmission, no turbo but station wagon with a good motor and worn differential bearings (50,00 fewer kilometers). The serial numbers were compatible and It was in better shape overall so my friend and I pulled out my transmission and installed it in the new car. All went well, despite the inevitable skin and blood donations ... lol. We changed the differential, engine and transmission oil, radiator coolant, etc and started it up for a test drive. The initial grinding noise was traced to the heat shield which ended up requiring some adjustment (done). Following that, we found the torque converter needed topping up. Needless to say, I drove a loaner home and left the car there. The last grinding noise/vibration/rubbing has us baffled (and he knows a great deal more about mechanics and cars than I do, I just provide the body, a sounding board and some minor analytical thinking with occasional spurts of imagination)

 

From a dead stop in reverse, all is fine. From a dead stop (under load) there is a grinding/rubbing noise with a vibration starting from the transmission and travelling backwards. We already swapped the new brakes over from the old Subaru so it's not that. The heat shield is good, the bearings as well, the driveshaft is clear and so are the wheels. It's been put into front wheel drive so it isn't the AWD. In first under load, the vibration and noise are prominent. In second if the gas is pressed heavily it's noticeable as well up to about 40 km/h. On the highway it comes back if kickdown is engaged.

 

Since the sound seems to have improved, I'm wondering if air could have gotten in to the transmission. If so, searches suggest that transmissions are self-bleeding, so I'm also wondering if i should floor it until it stops or take it ease (or maybe even play with the gears stopped, with a foot on the brakes). My problem with this is that it doesn't happen in reverse; is that possible?

 

If not, I'm hoping someone here has an idea of what else to check

 

I have recordings of the noises in m4u and mp3 but don't see how to upload them here.

[RumbleRumble]

To me with out hearing it, it sounds like the differential binding. Put it up on a lift or 4 jack stands and run it in 2,3,drive to see if you can pin point the noise.

[DaBlondDude]

In the air, there's no noise unless we brake, then it sounds like it's coming from the transmission. My friend suspects that too, as though the transmission is having difficulty properly gripping the gears when under load. That's also why the air bubble seems possible, as it would explain a lack of hydraulic pressure. Is there something that can be done about that?

 

If not, the differential bearings were shot on the other transmission but the rest seem d to be working fine, is there a part on that I should be looking at swapping over?

[RumbleRumble]

What trans fluid did you put in the tranmisson? What differentail fluid did you put in the diff?

[DaBlondDude]

The stuff the parts store looked up in a book. i forget the numbers, but I could call tomorrow and find out . If it helps, the bottle also had "gear oil" written on it.

Just out of curiosity, could it be the diff even if it shudders/grinds/rubs stopped with the brakes on? I'm still looking for a video/article explaining the nuts and bolts how of the differential and transmission work.

[RumbleRumble]

Trans fluid is Dex III and front diff is 80-90W limited slip gear oil

 

Put the FWD fuse in see what it does.

[DaBlondDude]

Oops, apologies, missed the second part of the question. Transmission was ATF Dextron 3, no viscosity rating on the containers so i assumed it was standard.

 

Diff was gear oil don't have the bottle for the viscosity but that sounds about right. It was what the parts tore looked up for that car.

 

It's already fused into front wheel drive. No difference.

 

My friends is wondering if the clutch pack could be worn, causing insufficient grip on the gears under load. I'm still wondering if it's air bubble that got in when we drained and refilled it and the torque converter.

[RumbleRumble]

air should subside and rise out the dipstick tube over time so I don't think it's a air pocket. Transmissions are not a closed system like brakes are.

[DaBlondDude]

Well, poop .. we added Lucas liquid repair in case the seals were tired and didn't notice a difference. Could it be the clutch pack? That "could" match the symptoms, I guess (this part should be okay on the old car if so, so it's a cheap thing to swap over).

 

Failing that, could moving, emptying and refilling have dislodged something that's now blocking a spring, seal, valve, etc? If so, perhaps a flush could fix that. I'm not sure this would only cause the vibration under load and then only in forward gears, though.

 

If not, I'm kinda stumped, so far.