Rough transmission and braking

[supercow2610]

Hi, i have a 2.5i with cvt tranny.

A few things:

The engine shudders more with a/c on

The transmission is more irratic at low speed (i.e stop n go traffic or rapid cycling between deceleration and acceleration at lower speed). It doesnt do a smooth transition even if i try to ease on the gas or the brake. I tried manual mode and chnaged gear ratio using a paddle shifter and the transition is smoother.

Brake is less sticky with ac on.

 

I have new belts, water pump installed at 100k. Most of the issues start with ac on but occasionally without ac.

Tranny fluid changed at 90k at Subaru dealer.

 

Engine mount, belt tightened n pump straining on the engine. I cant really think of any.

Anyone with similar problem or input?

 

Thanks

[1stTimeSub]

Did you ever get this resolved?

 

I had this same issue awhile ago also and took it into the dealer, they said it needed a new serpentine belt and per my request I had a drain and fill on the CVT at the same time, I noticed the problem was greatly reduced. That was about a year ago @ around 85,000 miles. I cannot confirm if they truly did a drain and fill - the dealership by me is hit or miss - but I think they did.

 

A little more info... I had the battery replaced because I was told by the dealer it was time to look into replacing the batter. So, I shopped around and got a battery that was well priced, changed the batteries out, and then... as I was driving to return the old batter, I had this irratic engine behavior going on with the A/C on. I got a check engine light after coming to a full stop at stop light. I can't remember the code, but it had to do with something electrical. That's what prompted me to take the car to the dealer. In my mind I thought the CVT was the culprit (which is why I requested the drain and fill on the CVT), but the dealer checked it out and said it was the serpentine belt. That makes sense to me since there was a new battery (new component to the electrical system), the belt drives the alternator (recharges the battery and critical to the electrical systems), and the compressor (which is why the a/c being on amplifies the issue).

 

I am noticing this issue coming back now. My car is just over 95,000 miles. I inspected the belt and it looks perfectly fine to me. I need to take the car in for the airbag recall and I am thinking about asking for a drain and fill on the CVT again. I do a lot of city driving so it wouldn't hurt anyways, but I'd love to know the root cause of this issue. Given my previous experience, I can't say it is the CVT, but I have read all around the internet that a drain and fill on the CVT is never a bad idea.

 

If the problem is still there, I'll try changing the serpentine belt myself since it is pretty easy to do.

 

Other thoughts I have had is:

- any of the pulleys attached to the belt could be going bad, including the compressor pulley

- Tensioner could be bad too.

[YeuEmMaiMai]

my trans acted funny at low speeds due to low relaxed my driving is. Talked to the Subaru dealer and they did a relearn. been fine ever since

[1stTimeSub]

Does a relearn cost anything at the dealer? Is it any different than what is described in an ECU relearn in the link below?

 

https://legacygt.com/forums/showthread.php/relearn-idle-after-battery-disconnect-257323.html

[YeuEmMaiMai]

that is for the engine control, not trans control. Trans relearn requires Subaru Select Monitor to be connected to the car. I asked my dealer if they would do it when I was in for an oil change and they did it no charge (I only paid for said oil change) but beware I bought the car from them and also have been going to them for the last 14 years as they serviced my 2002 CL type S, and still service my 2003 and 2014 Subaru Legacy cars

[1stTimeSub]

I just talked to the dealer and they wanted to do a more thorough investigation, which I don't fault them for at all.

 

But, he went on to say you should only do a TCM re-learn once in the lifetime of a car. Can anyone comment on this? Would more than 1 re-learn hurt your car? I'm not so sure I believe that.

[stewdogg]

I just talked to the dealer and they wanted to do a more thorough investigation, which I don't fault them for at all.

 

But, he went on to say you should only do a TCM re-learn once in the lifetime of a car. Can anyone comment on this? Would more than 1 re-learn hurt your car? I'm not so sure I believe that.

 

That sounds like BS to me. Did you ask him why? I would be very curious as to his reasoning.

[Loya1ty]

That sounds like BS to me. Did you ask him why? I would be very curious as to his reasoning.

 

The only thing I could think is that as the car's components age and run over time, the computer takes in the different variables from sensors and mechanics that works to improve the efficiency of the vehicle (which would be much different from a 0 mile car).

 

The computer being re-learned could cause some disparity between the 'real' function of the car and the 'ideal' model the program has when shipped with a new car.

 

All of this is me just spit-balling w/out any experience in Automotive computer chips and programming, but software engineering experience based on input and variable programming in general.

 

One could also make the argument that the re-learned program would cause the vehicle's sensors and components to function to spec rather than everything work together in a harmonious, but inefficient way.