Help My Mechanic Has No Idea? Gearbox Trouble

[QIK51X]

I have the exact same problem although my box isn't shift kitted yet its all just stock. Have had it serviced which still didnt fix the problem and it is only when the box gets hot. But the problem is exactly the same as how you have described, won't drop back gears and will only manual shift to 2nd not 1st.
I thought i was the only one who had this problem.
I don't see how the alternator would be the cause as its only when it gets hot? and same with the tps?
Any ideas? I am going to get my box rebuilt soon with shift kit and high stall which i was hoping would fix the problem.

My mechanic told me if the alternator hasn't got the right voltage it could make everything electrical play up. Thats why I changed it going on his word. If you are going to rebuild the whole box, Stage 2 shift kit is a must its the best mod I have done on my car. I let friends drive my car and most of them love it and giggle like little kids, but it does get annoying some days when your in traffic. Take my word for it get a stage 2 shift kit and definitely get the biggest aftermarket transcooler and fit that on aswell as it will keep your gearbox cool. :thumbsup:

The mods I have done to my car are:

-3.91 diff ratio
- Rebuilt motor (Crow Cams Stage 3 Cam Package)
- Rebuilt gearbox (Stage 2 shift kit)
- SS Inductions CAI + K&N Filter
- 2 1/2 inch exhaust custom made, Hi flow cat, hot dog resonator.

So far the car has done a [email protected] in this setup untuned. Not bad for a V6.:yeah: :yeah:

 

[tysons_2001]

yeah well i am going the turbo path so would be expecting a better time than that
And also was hoping the rebuild and shift kit would cure my problem.

 

[Rickman]

Hey, my gearbox had the same problem. The dash engine light would come on and the symptoms were the same - wouldn't kick down etc. Had it into the dealer and spent $700 dollars over 2 visits. They found error codes, but still couldn't really pinpoint what was happening. This happened about 3 years ago and it hasn't reoccurred. I have fitted a tranny cooler and found that changing to a new battery seemed to solve the problem. I would agree that it's electrical and I've now fitted one of those charger things that connect under the bonnet and leave it turned on. My car has a TH700 and is a Calais, which seem to suck power anyway !

 

[tysons_2001]

hmm so maybe it is a battery, alternator problem but i cant see how it only does it when the car is hot? i have a big sound system which sucks a fair bit of power which could be causing problems but it doesnt just do it when i have it turned up even if im having a quiet day just because its hot i run into trouble with no downchanges.

 

[Rickman]

It's definitely an erratic problem. Mine only really did it when it was hot as well. I reckon it goes into limp home mode, but don't really know why. I decided to live with it as I was only making the dealer richer. They replaced parts etc, but it didn't stop the problem. Anyway, it hasn't done it for a few years now so I'm pretty happy about that.

 

[tysons_2001]

Hmm so nobody knows the real cure to the problem?
Well i will soon find out if my auto rebuild will fix the problem.

 

[Immortality]

hmm so maybe it is a battery, alternator problem but i cant see how it only does it when the car is hot? i have a big sound system which sucks a fair bit of power which could be causing problems but it doesnt just do it when i have it turned up even if im having a quiet day just because its hot i run into trouble with no downchanges.

the ECU waits untill the engine is up to temp before it uses all the sensor inputs etc as these change as the engine warms up. i'd suggest it doesn't go into the limp home mode straight away, possibly with the wrong voltage in the system to begin with when the engine gets up to temp some of the sensor readings are far enough out of the normal operating range that the ECU goes into limp home mode. these cars seem very sensitive to voltage fluctuations

 

[QIK51X]

the ECU waits untill the engine is up to temp before it uses all the sensor inputs etc as these change as the engine warms up. i'd suggest it doesn't go into the limp home mode straight away, possibly with the wrong voltage in the system to begin with when the engine gets up to temp some of the sensor readings are far enough out of the normal operating range that the ECU goes into limp home mode. these cars seem very sensitive to voltage fluctuations

I think you hit the nail on the head with your last few words. My car is still running normally since the TPS, new alternator and trans cooler. I'm still trying to figure out which part fixed the problem. But i'm leaning towards the alternator problem and the voltage fluctuations. I should of changed one part at a time then I would of definitely known what the problem was.

 

[Immortality]

at least your car is now running and others will have a starting point if a similar fault occurs in there cars. and it never hurts to increase the collective knowledge on these vehicles

 

[digisol]

I see all this transmission talk and think of the real nice old lady with a stock VS sedan, now she is a definite lead foot, but I always heard the transmission upshift when she drove/raced off or up the driveway it always upshifted to 2nd.

Problem is it no longer upshifts unless she revs the clappers outa it and then backs off, one local mechanic has said there is no problem but I have heard different with the V6 reving way past 5,000 in first.

1st to 2nd 2nd tp 3rd needs to be coaxed in order to make it upshift and every change requires that she backs off the throttle fully, hard to do when all she knows is that R pedal makes it go, judging by the dents there are other ways to stop a VS other than the brake pedal alone.

So then, I was going to bung in a paperclip to see what the ecu shows but it would be handy to have a head start on what might be wrong.

Rest assured the thing is driven hard so the engine obviously works, although I have heard it idle at near 1000-1100 so it's a likely the tps or idle control valve are also stuffed, good thing the uni's work ok.

The car used to upshift quite normally now its reving on several thousand more before having to back off in order to make it change.

What ya reckon