Car won’t move after a sudden hard stop
 

Hi guys,

As the thread title states, my 7AT Z is having trouble rolling forward after a hard stop. I was out drying my brakes around the block after a wash to put the car into the garage. (I have to do this every time or else the Stoptech street pads will “weld” to the rotors). When the car would not move for about five seconds after hard braking and coming to a stop. I want to point out I just had the Trans fluid changed. Is this normal or is this a cause for concern? In the past I never applied the brakes until I came to a full stop, so idk if this issue just came about or I been having it.

Thanks in advance

Weird. I've never heard of the stoptech pads doing that but that's the first place I'd look. Too easy to change out pads and see if the problem is solved.

Thanks JARblue, I am not sure it’s the brakes but I’ll have a look. I am thinking of maybe going with oem pads. These leave a pad imprint every time I wash it . I do want to state that after the car came to a stop it would not accelerate it just revved for a second or two and then got going. It felt like it was trans related but then again it might be in my head since I just got the fluid changed 2 days ago.

Sounds like a possible trans fluid level issue. I have the Stoptech sport pads and they weld to the rotors after a wash if I don't dry them out.

If I wash my Z and leave sit overnight. My Carbo's will stick to my RacingBrake rotors. Nothing serious. They will break away easy. And there is an outline of the pads on the rotors. Around the block one time and it's gone.


OP, has this happened before?

I don't know how to check it unfortunately :(
I'll send the shop that performed the work an email and get their thoughts too. I didn't want to bother them with my assumptions if this is normal. So I figured I ask here since this forum has always been a great source of help. Thank you.

Yes, the pad sticking to the rotor issue I found out about when I bought the Akebonos to upgrade my stock calipers. They are coupled with the Z1 2-piece rotors.

The issue with the car not rolling after the hard stop is something I can't know for sure, as I just noticed it yesterday. :( When I bed in the brakes after the initial install I never came to a complete stop.

Yesterday is the first time I decided to stop as my phone had fallen out my shorts. That's when the car wouldn't roll forward. I was able to trigger the symptom at least 3 times.

I don't want to sound like I'm blaming the trans fluid change but like I said before the car revved freely for about a second or two then got going. It didn't feel like the time the pad got stuck to the rotor. I'm going to try it again tomorrow night when I get back from the gym to see if it acts up again.

The only way to get the pads to stick really hard is to get the rotors glowing red hot. Coming to a stop, and keeping your foot on the brake pedal until the brakes cooled completely. You're not doing any of this.

What you are describing is a tranny issue. You're coming to a stop. Step on the gas pedal. The engine rev's up, then the tranny hooks up. and then you move.

Yes, exactly as you summarized it in the second part of your post. At least it’s how it feels to me too. I’ll still do a couple of hard stops tomorrow night and will update on the symptoms. I will definitely get a hold of the shop if it persists. Thanks for your help. :tup:

OK, so it is definitely not the brakes I don’t think. I went out just now and applied the brakes in a mild and hard fashion and the car did the same thing. It stood still for a second or two then hooked up and rolled forward. I captured it on video from a decent stop. I hope the trans isn’t messed up, I was trying to prolong the life of it by getting that fluid changed :(

https://youtu.be/UpRGKRjNyfA

That's tranny issue.

FML :( I got a hold of the shop just hoping to hear back soon.

Sounds like the tranny is low on fluid after the fluid change.

The shop that performed the work will have a look at it tomorrow morning. I called Z1 and they said the same thing as Spooler. Crossing my fingers I didn’t sustain any damage to the transmission.

Thanks everyone who has helped me on this.

You should be fine.

Ok so it looks like it was low on trans fluid. The shop added some more and it is back to normal. Thanks again everyone!

If they don't know how to fill the transmission, there is at least one thread on this site that tells how to do it without any special equipment from Nissan. There is a procedure in the FSM but it requires CONSULT (or some other way to get trans temp).

Do they know the proper refill procedure? Simply adding cold fluid to a hot or cold trans isn't always going to do the trick. The fluid need to be at the correct temperature when determining fill level. I can almost guarantee you that was the problem when they did it the first time.

I did find a few threads on here on how to do it but didn't trust myself to actually perform it. That is partly the reason why I had a shop do it.

The shop is regarded as one of the best (Z shops) here in Southern California. The reviews online were mainly positive. But I am disappointed that they botched this job. Not gonna lie. They installed a Quaife diff on my car last year and haven't had problems with it, so I'm a little undecided on what to do for future service(s).

Ok so I am at a loss now. I feel I should have never messed with this a this point. The car is doing the same thing now but only when cold. After I got it from the shop yesterday it sat in the garage for about 4 hours and then my Dad and I went for a drive. No issues then. I got in the car just now after it had been off for about 24hrs and it did it. Once it got up to temp it did not do it. What should I do?

Sounds like the tranny fluid is draining out of the valve body over a period of time. Then takes a while for the valve body to refill.

Thanks Rusty, will more fluid fix this then?

Sometimes yes. Sometimes no.

It is still a little low. When the tranny fluid is cold it will contract. When it warms up it expands. You are still just a touch low.

Were there any issues with the car before transmission fluid was replaced?

The shop will look at the car again tomorrow. Hopefully 3rd time is the charm. I’ll update you guys. Thanks again everyone.

No not at all. I only did it to try and prolong the life of my transmission as I didn’t think the fluid was “immune” to degrading.

Maybe just add another litre and see what happens.
But I heard that overfilling auto transmissions can cause issues as well.

You should only add cold fluid to a cold transmission. Then you have to start the car and idle it for a few minutes to bring the fluid up to temp. The transmission fluid should be 104F in order to verify the proper fill level. Note that you may have to back flush the AT cooler to remove any debris that might have built-up.

Just a quick update guys, the shop saw the car Saturday and let the car cool for about 30 min. They then proceeded to filling it some more and I can confirm the issue is no longer there after I tested it cold. Thank you all.