View Full Version : Automatic Transmission Engine Braking

11-02-2008, 08:05 PM
Hey everyone, been a long time.

So lately, the main vein between my hometown and where I'm going to school has been closed due to a 'geotechnical hazard' (check it out, it's nuts http://www.arthon.com) and I've been forced to drive through a mountain pass to get between them.

Last night I'm coming down this massive hill, must be a 7% grade for at least 20km. I'm barely applying throttle, enough to keep a constant speed, then, after about 3KMs, all of a sudden the overdrive seemingly comes off and the engine RPM spikes to around 4k at ~110-120 km/h (speed limit's 110). I thought I had accidently clicked off the button, but engaging and disengaging had no effect. Thinking something weird had happened to the tranny, I put it in neutral, turned off and restarted the engine, but the gear was still engaged. As I wanted to conserve fuel, I simply put it in neutral and just coasted down the remainder of the hill (for a better idea of the steepness, I could maintain 120km/h in neutral). When the ground leveled out, I put it back in drive and it seemed to have switched back.

Anyways, long story short, I'm wondering if the (1990 GT) Celica AT tranny has some sort of automatic engine braking system when a certain amount of load is applied. I think this would be plausible, the computer monitoring TPS, RPM and speed have all the factors that indicate hill driving; however, in the 6 years I've owned my car I've never noticed this happening before. I guess I may be looking at some tranny wear here (~450 000 kms and still strong!).


11-02-2008, 10:07 PM
Huh, so there is someone who owns a 1990 with more kilometres than mine -- I'm sitting at a mere 320,000 km (haven't been driving nearly as much the last couple of years).

Not something I've ever noticed before either, but then I've not encountered a hill steep and long enough to reach 100+ km/h while coasting. However, the OD is based on having a certain engine load, so it's entirely plausible...

11-02-2008, 11:18 PM
Kickdown cable. Happens to me all the time on the highway. Its a matter of adjusting it in the right spot for your preferred driving style.

Tighter the cable, the longer you will stay in each gear (quicker), but higher chance the car will downshift on its own during stable speeds at increasing/decreasing loads.

Looser the cable, the quicker it will try to get into a higher gear (slower), better chance of staying in the highest gear.

11-05-2008, 07:43 PM
Well, isn't the kickdown cable really only a factor in throttle position? That's what I always assumed.

I had no throttle applied coasting down this hill.

11-05-2008, 08:08 PM
holy shit lol did you see the cracks in that thing dude any time now i say it will fall i'm glad they found that before it came down on some people

11-05-2008, 08:37 PM
Ok..... well its shifting, so its tied to the transmission in one way or another.

It doesn't matter if your applying throttle or not, if the cable is tight on its own it could do it.

( I can almost guarantee if you loosen it enough you will not need to worry about it downshifting on you....)

Well, isn't the kickdown cable really only a factor in throttle position? That's what I always assumed.

I had no throttle applied coasting down this hill.

11-05-2008, 09:15 PM
well on engine brakes "jake brakes" they activate when the throttle in closed so the kick down cable is probably doing the same thing the throttle is closed and the car is under a load so it down shifts making the car slow down and also since the car is slowing down it could just downshift because of the decrease in speed

11-06-2008, 07:17 AM
go adjust kickdown cable

11-06-2008, 07:31 AM
has anyone figured out how to convert to paddle shifters on these cars. Ive seen write ups for other car types. IE http://forums.turbobricks.com/showthread.php?t=47229&highlight=paddle+shifters+960

11-06-2008, 09:34 AM
I guess the real question would be, can you do it with factory ecu? or how?

I was looking at bgb online for 6th gens (5th gen wiring section was having issues) and I am not cool enough to figure that one out. yet...

11-06-2008, 10:30 AM
I did some homework, I guess aftermarket TCUs are the way to go...