View Full Version : How to know when slipping occurs?

08-11-2007, 05:25 AM
Ok first of all I have an auto. And second of all Ive only had this happen at full throttle. Since the auto only has 4 gears, they are spaced more apart. On first gear it shifts fine, right at redline, but at second, and grantid Ive only done this once..it seems "iffy" at redline in 2nd gear. By that time Im already going about 65-70MPH, and I dont know if its slipping or what, but just about at redline, I was waiting for it to shift and the needle went back and forth real quick, about a cm or so, and made a noise, thats similar to the sound in a game like NFS when your in manual mode and you forget to shift, and it scared me so i let off the throttle. What the hell was that? Was my transmission slipping?

08-11-2007, 06:25 AM
Bouncing off the rev limiter?

And your tranny shifts at redline on 1st every time? Damn. Either somethings wrong or Toyota is pretty brave in how they program their tranny's.

08-11-2007, 06:29 AM
i have a tranny slip gauge.

i wonder if you could get one for the celicas

08-11-2007, 06:57 AM
redline at full throttle.

08-11-2007, 07:16 AM
Dude you're hitting the rev limiter. There's probly a bit of slippage there thats letting you hit that high in the rpms before shifting.

If you wanna know why it's doing that. You answered your own question. Why are you redlining 2nd? It sounds like you're beating the hell out of it.

08-11-2007, 05:00 PM
But I dont understand, its an automatic its supposed to shift at redline, I dont see why I would have hit a rev limiter, It should have shifted?

08-11-2007, 05:22 PM
Ok it sounds like you're trying to race it from the 3rd party perspective. When you're in WOT the transmission won't shift until it absolutely has to. You hit the rev limiter that was the sound you heard. You just shouldn't have been at full throttle in that high of an RPM. If you're really worried about your transmission try this.

Go out and start driving get up on it in 2nd gear. Put the gas to the floor, when you reach 5k rpm let the gas almost all the way up. If you don't shift into 3rd you're slipping. Get it checked out. If it shifts then you're pretty good. You can manipulate the shifts this way, I don't know if you've realized it yet so if you have. Excuse the redundancy.

08-11-2007, 08:56 PM
So are you saying that if im full throttle, the car only likes it for the first 2 gears, and to get past that I have to let up a little , to get into 3rd and 4th? Im trying to understand this. I figured since its automatic, if i want to floor it, it should just redline 1st, 2nd, 3rd, 4th.

08-11-2007, 11:30 PM
It's not a dogbox. It's not made to slam gears at high rpm's.

The car doesn't like being redlined period. The transmission is setup for economy. A comfortable ride. You have overdrive for MPG reasons. It's not the mechanics of the transmission you need to understand as much as holding WOT to redline is a bit of a beating on an automatic transmission. The transmission has set shift points like 4-5k It's not soposed to shift for you like you're racing at the track. It will however hold itself in a gear longer if you're at WOT.

The GT-S automatic came with an option called ECT power. From what I've noticed it sets your shift point higher in the RPM range when it's active. It shifts maybe 500rpm before redline.

It's called the Red Line because it's where your tachometer tells you DANGER TO MANIFOLD!... well not exactly but danger period. It's neering the max stress limits that should be reasonably put on your engine. Thats why the Rev limiter is there. In the event of gear slippage or someone holding the gas down in neutral. It won't let your engine spin itself to pieces.

If you want to race with it, and slam into gears at redline. Do a 5speed swap. Or else you're going to have transmission problems worse than a little slippage.

If I'm wrong or not getting it... I can name about 10 people here who can easily correct me. So feel free to jump in if I'm wrong.

08-12-2007, 12:04 AM
Actually it determines the shiftpoints depending on how hard you press the gas. I think your not getting it, to be honest. I shift normally and dont beat on it all the time, only if i get into a race. Therefore, if your light on the pedal it will shift at 1.5k, 2k, and if you slam on the pedal, its SOPPOSED to shift at redline, because thats the max shift point set on an automatic. And I know why its redline, and I understand that the automatic is sopposed to shift at it at WOT, I just dont understand why it doesnt in 2nd gear.

08-12-2007, 12:17 AM
It determines shift points by Vac. You probly have a bit of buildup in the valve body. That would stop it from shifting properly in 2nd, but it would do it all the time not just when you're at WOT.

When you're too heavy on the gas vac builds up and holds the shift valve until a safer shift point. There are separate shift valves for each gear in your valve body. Each one reacts to different pressures, determined by the relationship of the governor and speed.

It sounds like nothing is broken, You romped on it and it held too long hitting the rev limiter in 2nd gear. You said it only does it when you're at full throttle. If there is a problem it most likely relates to the valve body. You said it only did it once. Have you tried to replicate it since?

08-12-2007, 12:27 AM
Hmm, alright thanks. I was just worried maybe my trans was slipping or something. I may try it again sometime this week. BTW cute cat in the sig lol.

08-12-2007, 02:33 AM
I have an automatic st. I don't beat on it "that much". But when im in a bad mood once a month or something i do tend to slam gears on the highway. A little hard driving once in awhile (not every day or even once a week) isn't going to tear a car apart. Now if you do stupid things like shift the automatic like a manual, or do neutral drops, that will kill it fast.

My automatic shifts about x300 before the red line, its hard to notice but thats about where it shifts. I have never had it "hesitate" when shifting when the gas is held down. All the way to overdrive.

I don't think your transmission is actually bad, otherwise it would have trouble shifting shifting at lower RPMS. Maybe change the fluid? I dont think you have much to worry about. I definitaly would do what your doing though if it was acting funny. At least until you figured it out.

on the 4th gen GT-S? Maybe GT, they had the ECT button or whatever it is too. When my buddy turned it on and hit the gas it actually went PAST the red line by like x400 nice little feature:)

08-12-2007, 02:59 AM
on the 4th gen GT-S? Maybe GT, they had the ECT button or whatever it is too. When my buddy turned it on and hit the gas it actually went PAST the red line by like x400 nice little feature:)

They were the 3sge I believe. Also I've heard of them liking the rev much more than the 5sfe.

08-12-2007, 01:55 PM
WAIT I KNOW WHAT IT IS!!!!!!!!!!!!!!!!!!!!


had to do this on my vert when had the motor put in, may take a bit of "test and tune" but u will get it how u want it eventaly

08-12-2007, 03:34 PM
Good thinking, that may be very well what it is...

08-12-2007, 04:44 PM
Keep It Simple ......... right :)

08-12-2007, 09:44 PM
PhillyDRFT: Since when does vac determine shift points? My 90GT was shifting at 1500-2000 rpm, even at WOT. Then I tightened the kickdown cable and it runs as expected. If I floor it, I have it adjusted to shift a few hundred rpm before redline.

I thought the autos shifted based on transmission fluid pressure, and with the kickdown cable, the more throttle you give it, the more it adjusts the pressure via the kickdown valve in the transmission.

08-12-2007, 09:47 PM
it only took several post for someone to mention kick down cable............. :slap:

08-12-2007, 11:38 PM
I never heard of a kickdown cable. When I learned Auto trans in school it was the valve body that ran from vac. Changing the pressures in the shift valve.

To shift properly, the automatic transmission has to know how hard the engine is working. There are two different ways that this is done. Some cars have a simple cable linkage connected to a throttle valve in the transmission. The further the gas pedal is pressed, the more pressure is put on the throttle valve. Other cars use a vacuum modulator to apply pressure to the throttle valve. The modulator senses the manifold pressure, which drops when the engine is under a greater load.

The manual valve is what the shift lever hooks up to. Depending on which gear is selected, the manual valve feeds hydraulic circuits that inhibit certain gears. For instance, if the shift lever is in third gear, it feeds a circuit that prevents overdrive from engaging.

Shift valves supply hydraulic pressure to the clutches and bands to engage each gear. The valve body of the transmission contains several shift valves. The shift valve determines when to shift from one gear to the next. For instance, the 1 to 2 shift valve determines when to shift from first to second gear. The shift valve is pressurized with fluid from the governor on one side, and the throttle valve on the other. They are supplied with fluid by the pump, and they route that fluid to one of two circuits to control which gear the car runs in.

The shift valve will delay a shift if the car is accelerating quickly. If the car accelerates gently, the shift will occur at a lower speed. Let's discuss what happens when the car accelerates gently.

As car speed increases, the pressure from the governor builds. This forces the shift valve over until the first gear circuit is closed, and the second gear circuit opens. Since the car is accelerating at light throttle, the throttle valve does not apply much pressure against the shift valve.

When the car accelerates quickly, the throttle valve applies more pressure against the shift valve. This means that the pressure from the governor has to be higher (and therefore the vehicle speed has to be faster) before the shift valve moves over far enough to engage second gear.

Each shift valve responds to a particular pressure range; so when the car is going faster, the 2-to-3 shift valve will take over, because the pressure from the governor is high enough to trigger that valve.

08-13-2007, 12:03 AM

Blue Scapegoat
08-13-2007, 12:48 AM
I hate autos. I had a 1990 Pontiac Sunbird with an automatic 3spd tranny. I only paid 500 for the car, so I beat the shit out of it for a good year straight. Tough little car. The gears were soooo incredibly long. 1st gear would take you to 50, 2nd to 80, and 3rd to 105. I learned how to manipulate the tranny to my advantage, just how much to lift up on the pedal and at what points on the tach to get it to shift when I wanted to, and so on... not really helpful to you, but just thought I'd throw that out there.

I consider autos cruel beasts. They're all different and finicky, and get screwy with age and wear and tear. But eventually you'll learn how to get the best out of it

08-15-2007, 08:10 PM
so did i fix newbsters slipping trans? :hehe: