Quick Question. Vx V6. auto
Hey all.
Just got a quick question. Its hard to explain but ill give it a shot..
In a VX V6 AUTO, When you are traviling at speed and u drop down gears does your car slown down rite away? as in compression breaking?
Coz in my vx when i drop down to say 2nd gear the car will feeel like its still sorta accelerating as in the throttle is still partly open,
But after 3-4 seconds it will start to slow thrugh compression breaking.(no vaccumm leak's or any other leak's)
.
In my VP V6 AUTO when u put it down gears it would start slowing right away! and the exhaust would pop and do all the usual slowing under compression things.
But the VX wont, the exhaust wont pop or anything untill like 5 seconds later then it will start to slow as the VP did..
not into the exhaust pop just that i know my vp did it right away but the vx is diffrent.
It has done this with the old VX motor and the new VY motor....so may be normal to all vt-vx-vy??? dont know....
but i really hate it!!! u try use the gears to slow u down in an emergency or something but it does absolutly nothing..
Its def not a gearbox issue because u can fell the gearbox is doing its job, just the engine is not...
So its sorta like this- driving along then drop the gears and the gearbox will drop down as normal and the engine RPM will go up but the car will not slow at all. untll 3-4 seconds then it will start compression braking. almost like there is a valve in the TB that stayes open to prevent cool people from trying to be cool..wich we all know there isent!
Thanx guy's
Phatburger fanatic
Maybe someone else more knowlegable than me could offer a better explanation than this, but I would first question what speed you are doing when you downshift. The transmission has a torque converter lockup clutch which is operated by the PCM at various speeds. I have the official holden tech CD so can look up the page that describes the operation of the TCC, but I suspect what you might be experiencing is a lag to disengage the TCC. That could be due to the speed you are traveling at being above 120 km/hr or it could be that you are not simultaneously applying the brakes which should immediately disengage the TCC under normal operating conditions. Anyway, just a thought and as I say, someone else might have a better suggestion...
as far as I believe the torque converter will lockup at about 90km/h.
but depending on what speed your doing when you downshift, as the transmission will not downshift if you are exceeding the gear change speed, for example if your doing 110km/h and downshift to second, it won't actually change to second until your speed has decreased to 90km/h. I believe they designed them that way to prevent compression lockup or engine over rev. (if you downshift to 2nd at 110km/h your back wheels would lock up and cause your tacho to hit redline) i'm not 100% sure on what speeds the transmission will downshift.. but you could possibly read up on this.. it was more a safety feature which I think was a good idea, as I had a VK auto, and when going to overtake I would manually downshift to 2nd and on the odd occaision I pulled it back to 1st and nearly put myself off the side of the road due to the compression lockup..
the transmission speed downshifts are something like
4th - 3rd @ 110 km/h
3rd - 2nd @ 85 km/h
2nd - 1st @ 40 km/h
Like I said I am not 100% sure on the speeds, but this should give you a bit of an idea..
here's another post on a similar topic not much info there though
SIDI SV6 SERIES I Auto - Downshift rev-limiter
Thanx for the info, But even if i am doin 40k-50k and go to second the car wont slow, it 'feels' like the engine has no compression but obvisly it does. but after the 4sec it will act as normal as my old vp did. im goen to powercruse this weekend but when i get back i will take a video of what it does and how it acts. im sure its a VX thing but its just a bit annoying i cant use my gears to slow down.
If i put it down to say 2nd gear doin around 50-60k it will actually be harder to slow for a roundabout or such because its just keeps acelrating ,
But yeh ill get a vid when i get back
Thanx for the help!
maybe your accelerator cable is a bit sticky in a certain spot. (with the engine off) take your air intake pipe off the throttle body and open and close the butterfly by hand and see if there is any restriction there and check the spring has a bit of force to re close the butterfly. also see if there is any carbon built up in there. if there is get a throttle body cleaner spray and give it a good clean. if there is no restrictions in the throttle body, undo the accellerator cable and see if it is sticking anywhere. other than that it could be a computer glitch, disconnect your battery for about an hour this should reset the computer in the car and see if that helps.
check your air filter element also, if it is getting a bit dirty it can cause your engine to run a bit rich, (less air to fuel) and on decelleration the engine could be burning the extra fuel in the manifold before it starts to slow. (long shot, but check the air filter)
have you also checked for fault codes logged by the computer. I think you short terminals 5 and 6 together and count the flashes of the engine light on the dash, the first set of flashes is tens and the second lot is ones, if everything is normal you should get code 12. 1 flash (short pause) 2 flashes... if you get any other code, check out what it is.. (again possibly a long shot, but it's free to do and it is easy so why not)
Automatic transmissions are not designed to be used as brakes, period. Pulling them into lower gears has a similar effect to towing with motor turned off. It can and will destroy your transmission over time, very short time in some cases. Ask your experienced Holden tech/mechanic about it. Or any automatic transmission repairer.
there is no stickyness, no carbon buildup as i clean that frequently, new air filter and no faults logged, hmmmm...
I recently reset the computer so unfotunatly that dident fix it, great help tho thanx!
Oh and to graham- im not using my gears to slow down frequently, i only wanted to try fix this problem incase i ever Need to stop a bit quicker in an emergancy. and plus i would like my car to act as normal as of right now its not.
even my car not slowing down from lower gear changes could indacate a bigger problem that i would like to get fixed thats all... im not a young P plate driver who does it all day long to make the exhaust sound good... just simply want to find out why my car is not doing as it should..
I will try get that video asap, but was thinking it may not be the best because you prob wont be able to hear what the motor is doing, it will only show what the RPM is doing.. but ill give it a go anyway..
So i guess this may not be a VT-VX thing as i first thought? must only be my car...
Have you tried putting it in power and doing it?
I notice that in economy the downshift is pretty bad,But in power it is quite different.
I use to have the problem of the car coughing a bit when it would shift down a gear.
Then one day when I went to leave work it wouldnt start,Was turning over but getting no fuel.
Got it to the garage and they said the fuel module had shit itself ( think it was the module )
But had it fixed and it runs so much better now,No shuddering on downshift or coughing and farting.Just a nice quick clean shift.
did you figure out the problem by any chance?
I have a similar problem. I have had the gearbox stripped down and looked at but there is nothing wrong with it. gearbox guys said its a engine problem
bad for transmission dude... not to sound rude but my advice: If you want a manual... buy a manual... not a "semi-auto" tiptronic, or an auto... a proper manual car with a clutch.
its not bad for the transmission if it is built for it. I have a stage 3 which is built for manual shifting. Stage 2 and 3 are more popular then manuals because they can shift faster then what we can in a manual. I have had manuals and i wouldn't swap my auto for a manual
I drive my auto like a manual a lot of the time, and Ive never had a problem with it. It still shifts etc as good as the day I got the car,and Ive done around 200,000 k's in it now. I do service it regularly though. Every 20,000 k's for the auto trans, filter and fluid change.
Last edited by Brett_jjj; 01-05-2012 at 06:31 PM.
It is bad for a standard transmission, I never said anything about a shift kit. Obviously they are purpose built for heavy duty application. Ask any mechanic, and they will tell you, an automatic transmission is built to leave in drive, the only reason you should be in 3, 2, 1 is when towing a heavy load, up a hill. Other than that, to leave it be.its not bad for the transmission if it is built for it. I have a stage 3 which is built for manual shifting. Stage 2 and 3 are more popular then manuals because they can shift faster then what we can in a manual
Even though you shift like a manual, you are still taking the time to examine and service your transmission, which holden only does every 80,000k's or something like that (somebody confirm). It's called preventative maintenance, and is a good thing.I drive my auto like a manual a lot of the time, and Ive never had a problem with it. It still shifts etc as good as the day I got the car,and Ive done around 200,000 k's in it now. I do service it regularly though. Every 10,000 k's for the auto trans, filter and fluid change.
My auto is just a standard 4L60E. The owners handbook that comes with these cars says that the lower gears can be used to slow the vehicle etc. Heres what it says about using the auto transmission in the VN handbook,which is the only model handbook I have handy at the moment,
3rd or Drive (D)- Most effective when overtaking and gives responsive acceleration and deceleration, especially in hilly areas.This position allows the transmission to shift to first, second and third as conditions require.(overdive 4th is excluded).
2nd Second (2) - Use this position when going down a moderate gradient where you want to slow down without using the brake.The transmission will shift from first to second as required.
1st First (1) - Use this position when a strong breaking effect is needed on steep gradients.
Theres nothing mentioned about towing uphill and shifting down, the auto will automatically shift back to the required gear anyway when going uphill.
Last edited by Brett_jjj; 01-05-2012 at 07:00 PM.
That would be under load (towing) or on a gradient, where there would be constant braking (as you had said... otherwise you boil brake fluid, causing failure)... slowing down to get to a corner on a normal road, or when approaching lights, it would be smarter and safer using your brakes cause you are braking... when you are engine braking you car still creeps forward... but think about it this way...
What's cheaper? New brakes? Or new transmission?
What would you rather replace? A brake disc, a few pads and some fluid, or a transmission?
What's cheaper to fix/replace? Braking components or transmission?
What will leave you stranded? A failed brake or a failed gearbox?
great conversation and all but does anyone have a answer to the forum question by any chance? this problem is really starting to annoy me. it doesnt happen all the time, just every now and then. is there any chance this could be a vacuum problem?
If the auto is not shifting up or down properly, but the transmission itself is all good, then check the TPS, as the ECU uses info supplied from the TPS to help control the auto's shifts etc.
Last edited by Brett_jjj; 02-05-2012 at 11:07 AM.
If the lower gears were not supposed to be used or selected manually in an auto transmission, then the shifter wouldnt even have the option to shift back to first, second or third etc. And you can still use the gears to help slow the car down along with the brake, it doesnt matter if its auto or manual, shifting back will help slow the car,manual or auto, and it doesnt matter if you have a load (towing) on the car or not. .. if the auto is kept serviced properly etc, it wont wear it out any quicker than it normally would, and it wont break anything.Originally Posted by Sizzle87
Most auto failures I see are either from people who dont know how to be mechanically sympathetic to their vehicle, or when they dont keep it serviced regularly. Also driving the vehicle hard when the engine and trans are not up to operating temp will shorten their life considerably. I just pretty much idle along in my car until its fully up to operating temp, then I hold it flat everywhere.Hehe.
Last edited by Brett_jjj; 02-05-2012 at 11:35 AM.
Hey guys, Nah no fix yet unfortunately (errrr), Although i can confirm it is not:
vacuum leak. <--- all checked and well!
gearbox issue(hardware) <--- all well there too!
engine low on compression <---all good!
sticky throttle. <--- free as a bird!
Like i said, i never downshift gear's to be cool, Only when needed, like to prevent burning out brake's..
BUT, just the other day i tried downshifting again to refresh my memory as to what the car does AND previosly i had never really downshifted to 1st, only really from 4th to 3rd to second, BUT the other day i was doing ohh id say around 40kph then i downshifted from D to 3rd to 2nd then 1st and seriosly, when i got down to 1st i was doing maby 20k - 25k and the car would not stop.
Rpm's went up as all cars do but they just stayed there, just kept driving along like i had cruse control on wich i dident, it was so wierd, Like i had felt it previosly doing this hence my first question but never had i gone down to 1st at such a speed. it's so wierd, the car just keep's on driving like i have my foot on the accelerator.
I have spoken to quiet a few trans places but they just look at me like an idiot and say they have never heard of this before, SO i really dont know how to solve this!, Like i said i do know it's not the gearbox its self because you can feel it's doing what it's sposed to, It's just something to do with the engine....But the engine is fine, no vaccuum leak's, no issue's at all, also no fault's logged....
It is an ex cop car, well not the one's with police sticker's all over but i think it was a detective's car or something, sice then i have put a new VY engine in, and still has this wierd issue....
Like im sure it's not sposed to be doing this, every other car i have driven when u drop the gears the car start's to slow down, you can feel it pulling up, But not mine...
feel's like i still have my foot on the accelerator slightly ( i don't), But it's def not sticky throttle...
ONLY thing i can come up with is some sort of odd tune someone may have put on??? maby the police? some sort of feature they like??... i dont know enough about tuning to be sure though...
what else could it be??
Once i get a chance ill record & add a video here (can u do that here?), it may not help to much as you more than likley will not be able to hear the engine but ill give it a go.
It's really annoying and just want it solved.. You dont know what you got till it's gone!
EDIT: Just recorded a video but can not get it on here...It's 16.5mb and cant get it smaller so no go.. any idea's??? the road was on a slight incline so rpm's were dropping more that they normaly would...
Last edited by vx_commodore; 02-05-2012 at 10:20 PM.
Posting Permissions
1Likes
LinkBack URL
About LinkBacks
Reply With Quote