Rough Transmission (6MT) After Car Sits In Garage For a Week. Why?

[Veloist]

My BRZ is not my daily driver and I normally drive it once every 7-10 days for about 25-50 miles. Other than that it sits in the garage.

I notice that everything about the transmission pretty much sucks the first day when I get back in my BRZ. The RPMs drop differently, the clutch has a numb and higher engagement point, and the revs don't drop quick enough.

Now say the BRZ sits for 7 days, I drive it 25 miles on the 8th day, and then drive it again on the 9th day. On the second day of getting back in the BRZ, everything about the transmission is exactly how I know the car is supposed to feel--a precise clutch engagement and the rewarding notchy shifts. I can describe as "Smooh and Precise."

My main questions are...

What is happening to the transmission when the car sits for a week? Does It have to do with transmission fluid or other fluids moving away from the gears? Does anything temporarily dry up?

Why does it take at least two days or 50 miles for the transmission to feel proper again?

And here's a twist...

Does this phenomenon apply to cars that are parked outside where it reaches 70-75 degrees throughout the day? Because I work at a dealership, normally when I take a BRZ out of our lot, the shifts feel perfect even after they've been sitting too. Sometimes when I drive my car to work and park it in this warmer climate, it feels smoother even though it's the 1st day back on the road. Does it have to do with heating of the metal and heat radiating from the ground to the transmission?


I've owned my car 10.5 months and it has 2800 miles on it. I shift around 3000-4000RPM. Mostly short city and highway driving. Average temperature of my home's outside climate is like 55 degrees thought daytime and nighttime, so my car is usually sitting in my garage that is about 60 degrees most of the time.

Really curious about this. I'm more amazed than worried, if at all. Would love to hear some insight or other experiences. Thanks!

[cjd]

My car is garaged, but it sits for weeks (and during the winter, months) without being driven and I only notice the usual cold start symptoms with shifting... Easy to deal with by holding rpm a second or two before shifting, and usually gone during the summer by the third or fourth stop/start.

OEM and Motul behave about the same. 12,6xx miles since May 2014.

[Drakiv]

I would think that the reason is all the oil has moved away from the gears not necessarily drying up parts but just getting down to the lower half, and then the oil is cold. You do short little drives and the oil doesn't have a chance to really warm up in the trans, and then after your couple drives the oil has gotten around the gears and in the passages and even being cold is decent. If you have stock fluid, I would change it to something like Motul or equivalent and it might help some. I don't think you are causing any serious damage, but your synchros are probably getting a little angry. That's what I think is going on, someone correct me if you think im wrong.

[ZionsWrath]

It's a machine. If you don't use it you lose it!

25 miles once a week

[humfrz]

Oh, I wouldn't worry about it if I were you.

Heck, at 2,800 miles.....it's still breaking in.

Just drive it more ...... it will be happier .....


humfrz

[PMPB]

Hot, evenly distributed oil is what this transmission was made to run with.

I notice the same thing as you. If the car sits, the transmission feels clunky and loud, it's not good until I have probably 20km. If I drive it every day, it's quicker to get back up to feeling "sweet", maybe only 8-10km (just about the time I arrive at work).

[Romanov]

I see you've converted your BRZ in a large paperweight.

Just drive it, most likely the transmission syncros haven't fully broken in and the lack of transmission oil/diff oil distribution causes it to be not happy after sitting.

[wparsons]

I wonder how much is in your head, and on the second day it just feels more comfortable since you drove it the day before? I've been house sitting for a relative for years and cycle through their cars when they're not home, every time my car feels really odd to drive after driving one of theirs for a couple days. It's happened with every car I've owned, not just the FRS.

[Veloist]

I've driven the car almost 300 miles in the last 4 days lol and the transmission definitely feels smooth as butter.

It could be a mental/motor-skill thing but like I mentioned, when I drive the brand new BRZ's at work to move them or bring them to a test drive, they feel fine so I don't know if it has to do too much with breaking in.

I'm convinced to believe that the more the car is used the better it will feel on subsequent days.

[GotMunchies?]

It is very common for transmissions to feel rougher after sitting for a period of time. When not in use, the lubrication of the gear sets will drain off over time into the sump of the transmission.

Most automotive (and many industrial) gearboxes lubricate by spinning the gears through an oil bath in the sump (bottom) of the transmission. As the gears spin, the oil is transferred to the various rotating components of the gear-train. As long as the gears spin and there is oil in the sump, the oil will continue to lubricate. At rest, gravity does its' work and the oil will slowly drain into the sump and remove lubrication from the gear train.

Here's a good video that illustrates how it works:
[ame="https://www.youtube.com/watch?v=s7ZS1t7Y3po"]Lubrication Engineers Gear Box Demo - YouTube[/ame]

[Veloist]

Thanks for the video!

So this is the most I've ever driven the car in a 5-day period and I can confidently say that there is a difference in how the gearbox acts when driving it consecutively. It's buttery smooth meaning I need less effort to throw it into any gear especially the dreaded 1st to 2nd change.