I just bought a 97 Legacy Outback. It's my first Subaru and first automatic transmission. I'm noticing some strange behavior from the transmission and I can't seem to put together the right keywords to find anything about it.

When I'm at a stop (at a light or in traffic) I can feel the transmission engage suddenly and try to pull the car forward. It doesn't happen all the time, but I'll be holding the brake for a while and then the transmission will kick in, the RPMs drop, and if I'm not on the brake hard enough the car will start driving forward as if I'm pressing the gas. 

It can't be good for the transmission to be fighting to drive while I'm fighting to hold it in place. I've been reading up on torque converters, but I don't have much experience with autos. Any ideas?

What is the fluid level? First things, always check the obvious. But usually if the fluid is low, you have a hard time engaging. More feedback please. 

I've checked the fluid. It's full - probably even a little higher on the stick than it should be.

How high is it idling? Should idle at around 750. If it's pulling hard when sitting still it's probably idling too high.

 

These have a somewhat common issue with delayed downshifting when stopping or when stopped. The trans will hang in third or second gear. The jolt you feel is when the transmission finally kicks down to first gear. High idle will cause this.

 

Always a good idea to change the trans fluid if you suspect a transmission problem. Even if the fluid appears clean it can often be worn out without looking so on the dipstick.

I have to ask since you're new with autos, are you checking the fluid level with the engine running and checking the correct dipstick?

 

I've had customers check the front diff instead or check with the car off.

 

Out of curiosity is there any correlation with anything else happening, like the ac clutch kicking in?

I have to ask since you're new with autos, are you checking the fluid level with the engine running and checking the correct dipstick?

I've had customers check the front diff instead or check with the car off.

Out of curiosity is there any correlation with anything else happening, like the ac clutch kicking in?

I did some more troubleshooting today. It seems my first description wasn't quite accurate. The RPMs weren't dropping, they were increasing slightly. Once I realized that, I found that I was able to trigger it by turning on the lights or fans. This leads me to believe that the change in RPM was caused​ by the alternator clutch locking. The increase in RPM was applying more torque to the transmission, which was giving that pull that I was feeling. This seems like the normal operation of an automatic transmission and I'm freaking out about nothing.

 

I was checking the trans fluid with the car warm but off, so I'll be sure to do it right in the future. Thank you guys for putting me on the right track.