Manual Downshifting on Auto

[AWD Chaser]

Today, I was approching a roundabout and downshifted to second and then to first, but when it hit first, the rears locked up, and the back started drifting out. I only got it going again by giving it some foot which got the rear wheels rolling again.

The rtoad was dry, I had already been driving for over 30 mins (so tyres were warm), and they have plenty of tread... Has anyone else had this in the dry?

[janek]

you just kicked it down too early mate... the BTR 4 speeds are a little wierd on quick gear changes

[ClassicAU]

sounds to me like compression lockup i think. if i ever down shift it to first, i try not to do it above 60km/h just to be safe. how fast were you going when this happened?

[Fairlane]

i downshift all the time and am yet to have a compression lockup, thats a weird one considering how long the BTR first speed is.

Then again the BTR's are a funny box.

[AUIIForte]

Does sound like you where driving abit fast... Ive swtiched into 1st fron 'D' while going at about 70km/h by accident (meaning to hit second), but the wheels still didnt lock up, so im thinking that you must have been going abit too fast...

[AWD Chaser]

I was already in second approching a round about while lightly applying the brakes... down to first and lockup... i may have been going a bit fast for 1st, but def not more then 70....

[Mechan1k]

I only downshift to 1st if under 40km/h (and that would be maximum) .... only times I do it is under heavy load ... or towing and having to come to a stop ... just so i don't overload my brakes.

Any higher speeds than that ... and your gearbox will have a premature death.

Also when downshifting ... i do it smoothly ... nothing quick ... and i make sure revs aren't high either.

Be kind to your transmission ... and it will be kind to you (ie: will not cack it's pants and leave you with frigging expensive repair bill).

[galaxy xr8]

I thought down shiffting in these auto's were BADDDDDDDDDDD.

[Mechan1k]

It is .... but if you have to ... do it nice and gently.

[NEG]

yeh what Mechan1k said.

iv changed into 1st doing about 50 and nearly hit my head on the steering wheel. I would rather replace brake pads a little sooner than have to get the tranny rebuilt.
also with the comment about tyres being warm, steet tires arnt the same as racing tires they dont gain grip as they warm up. Normal street driving wouldnt 'warm' them up anyway.

[AWD Chaser]

Originally Posted by NEG

yeh what Mechan1k said.

iv changed into 1st doing about 50 and nearly hit my head on the steering wheel. I would rather replace brake pads a little sooner than have to get the tranny rebuilt.
also with the comment about tyres being warm, steet tires arnt the same as racing tires they dont gain grip as they warm up. Normal street driving wouldnt 'warm' them up anyway.

Compared to straight out of the carport in Canberra -2 weather... yes, the tyres were actually warmer then when I firt stated the car... anyways... no more downchanging to 1st for me then...

[The Monty]

Yeah I only downshift under 60. Anything over that and things get too fun. Especially in the wet.

[4.9 EF Futura]

If the AU BTR is anything like the s-series (which it is) then you must be REALLY keen to shift down into 1st???

Did it a couple of times at around 40. You know when you do something to a car and you can tell the car really didnt like it? Well... that was one of those things. IMO 1st gear in pretty much any car is too short to be selecting in "normal" driving. - from a beautiful 4 speed AU to a ratty manual datsun...

You can generally tell with these boxes when they're not happy about something the operator has done. If it feels good, do it. If it doesnt... then dont. lol.

[galaxy xr8]

I must addmit I have downshifted but only to 2nd never to 1st, and if I do have to go to 1st it's only when the vehicle is nearly at a complete stop, not at any great speed.

[XR6-VCT-2000]

Compression lockup .. lol , yeah good way to crack ya head on the windscreen / head-but it ..lol , I've done it in the past too ..lol . And yeah as Mechanic mentioned you will kill the tranny kicking it back like that !, according to most manuals/handbook specs for most trannys you especially shouldn't even be shifting down from second to first manually, unless towing and it is absolutelly required ( to get up a hill or something with a heavy load ).
But im not saying don't do it ! , just try to keep the revs lower when changing back , so at least then you'll get a bit more problemless life out of the auto . Even constantly shifting back the auto to first gear to slow down around 45kmph and above is gonna trash it in a pretty short time , give or take the odd few 'freak' auto's that never seem to give-up ! ..lol

[Dark Horse]

Lol I'm not going all out to test if mine's a freak auto or not.

But yeah, some keen manual action auto shifting driving going on here...

[AWD Chaser]

You know how these commodores work you up when your driving to work....

[XR6-VCT-2000]

Originally Posted by au3 chaser

You know how these commodores work you up when your driving to work....

Hehehe , sure do ;) .

Just to mention too , heavy braking at high speeds with majorly front biased brakes can cause the butt of the car to lift a bit and the nose to dip / causing the rear wheels to loose traction on the road and the rear brakes lock ;) .

[DOC]

Originally Posted by au3 chaser

I was already in second approching a round about while lightly applying the brakes... down to first and lockup... i may have been going a bit fast for 1st, but def not more then 70....

As others have said, you slammed it down to soon, and by what you have written, way to soon but all good, when and if needing to slam to first, not as above where your lightly on the brakes = no, you would need to be slamming them on hard before even thinking of going to first, even then as you say you were nearing a roundabout, the time to hit first would be when coming out of the roundabout i.e foot of brake, slam first, foot to floor.

timing but you will get there, and yes this all happens in the saftey of a track enviroment :

[SVR73]

AU's really hate being above 30 when going back to 1st
have had two of em and I downshift always, all other gears are fine but whenever you go into first too early, the trans/diff clunks
I shift down to first at no more than 20 and with accellerator off and it's fine
Did it in the forte a few too many times and fortunate to not damage the tranny

[JC]

Originally Posted by SVR73

AU's really hate being above 30 when going back to 1st
have had two of em and I downshift always, all other gears are fine but whenever you go into first too early, the trans/diff clunks
I shift down to first at no more than 20 and with accellerator off and it's fine
Did it in the forte a few too many times and fortunate to not damage the tranny

Same here. I down shoft all the time, but only ever as far as 2. the car sorts itself out if it wants to shift all the way down to 1 - and being an eight, it does it more often than not when accelerating hard from a slowish speed (up to about 50). I do use first off the lights though, and when I want to hear that glorious V8 burble on throttle down.

[The Monty]

I find if you dont want the gears to clunk while downshifting, you have to release the brakes at the time of the shift. I never get a clunk except if Im on the brakes at the time of the shift. It still feels as if you are braking, as the engine takes over the braking for a sec, so its still a continuos brake, but without the clunk.

[AUIII XR8 MAN]

I down shift mine to frist all the time. I found that if your going to fast it will not change down untill it reachs the correct speed even if i put the selecter in frist.

[JC]

Originally Posted by AUIII XR8 MAN

I down shift mine to frist all the time. I found that if your going to fast it will not change down untill it reachs the correct speed even if i put the selecter in frist.

Yep, that's the in-built safety for the auto trans. After getting mine rebuilt 12 months or so ago, the trnasmission guys recommended not to downshift to first manually. They said second's OK, but first tends to wear faster if you do that. They did say that selecting first for a standing start is fine - just upshift before you hit the rev limiter.

[sednwol]

I down shift mine to frist all the time. I found that if your going to fast it will not change down untill it reachs the correct speed even if i put the selecter in frist.

Pardon my ignorance but does the XR8 have the same box?

[XR6-VCT-2000]

Thats the same for any auto really , if your going way to fast for first gear then drop it back to first gear then it will hold off until it is within the max rev range of first gear, then just about throw you through the windscreen when it does drop to first gear near redline ! / and prolly get the rear end lockup for a split second ..lol . Not good for the tranny , or yourself / whip-lash ..hahaha

[autickfordfairmont]

I always downshift however only to first when really slow 30km/h or less, normally less, if i need to take off it will kick down by itself at those speeds. If im having a run from the lights i will only change when basically completely stopped, then change up when i hear the ***** scream, oh i mean before redline.... haha, have only ever had the rear end lock up from downshifting and that was in the old ea, somehow when i slipped it back a gear it jumped a little to far (Worn Gates didnt always need to press the button) and hit first at about 95Km/h, *** end went out a bit, but i soon hit the breaks pretty hard to pull her up so she wasnt having an internal hemrage for to long. But that box was pretty ****ty anyways, would drop into second very very hard and chirp the rears all the time, with no shift kit installed, and soon enough it died, chewed the hell out of itself.

Cheers.