Slightly scary (and dangerous) Auto shifting 'problem'

[MA70_Powa]

Hey guys,
I have a bit of a 'problem' with my car and it's shifting habits. Before I start, its an Auto with a 4.3 LSD.

Basically, I've had a shift kit installed in the transmission which cuts the shift times down considerably. Now, the problem I'm experiencing is that sometimes when it shifts gears while I'm on boost the rear end will kick out to the side (usually to the left) and I'll do a mini fish-tail until it stabilises and then keeps going. I've noticed that this happens more when I'm going around a slight corner rather than straight, and I've almost gone into the other road lane more than once.
(also, slightly unrelated but when it shifts I notice my boost can spike a little bit - used to make me hit fuel cut before LEX/550s lol - is this normal?)

Is there something I can look at to combat this? like subframe bushes, diff, driveshaft, etc? or do I have to live with it since I'm making massif powaaa lol

 

[aljordan]

Run stickier tires.

 

[Turbo Habanero]

wider tires might help..Stickier too just put some big ass monster truck tires on there they wont spin

 

[aljordan]

wider tires might help..

Wider does not help with traction. Only contact path (deflate tires) and compound will achieve more grip.

 

[Turbo Habanero]

Wider does not help with traction. Only contact path (deflate tires) and compound will achieve more grip.

I thought maybe it would help from sliding out around corners as he said it was doing.

 

[lewis15498]

Hey guys,
I have a bit of a 'problem' with my car and it's shifting habits. Before I start, its an Auto with a 4.3 LSD.

Basically, I've had a shift kit installed in the transmission which cuts the shift times down considerably. Now, the problem I'm experiencing is that sometimes when it shifts gears while I'm on boost the rear end will kick out to the side (usually to the left) and I'll do a mini fish-tail until it stabilises and then keeps going. I've noticed that this happens more when I'm going around a slight corner rather than straight, and I've almost gone into the other road lane more than once. (also, slightly unrelated but when it shifts I notice my boost can spike a little bit - used to make me hit fuel cut before LEX/550s lol - is this normal?)

Is there something I can look at to combat this? like subframe bushes, diff, driveshaft, etc? or do I have to live with it since I'm making massif powaaa lol

Simple fix, learn how to drive.

 

[MA70_Powa]

lol when I say slight corner I mean maybe like 10-20 degrees off straight, not like a 90 degreee turn...

And I probably shouldve said before, I've got 9" wide wheels on the back and 8.5" on the front - with relatively new tyres.

Guess I could try deflating em a bit. But it truly is random when it happens, which is the annoying part!

 

[Moy]

well... the shift kit, making the shifts more firm, probably cause the rear tires to "chirp" or momentarily lose traction. you'll kick the ass out in a turn for sure if you lose traction, even if only for a split second

 

[lewis15498]

I have no idea what this "shift kit that drastically improves shift times. Autos shift instantly compared to a 5spd. Thats why they are preferred for drag racing as they hold boosts between gears.
Your issue is your throttle input. This isnt a pickup with a 22r. You give it too much power its going to kick out on you at even the slightest angle. sometimes even in a straight line, regardless of if its shifting fast or not.
Your tire has a max amount of traction. This changes depending on may conditions, were not going to get in why. the front tires job is to dictate the direction of the car. The rears A provide traction to propel the car forward, and B hold the car in place and fight the lateral g in a corner. as your speed increases soe does the grip required to do that. A 15degree turn at 60mph creates more lateral g than at 30 mph.
If the car is going straight ahead with no outside forces, (this rarely ever happens as even the slant on the road to help rain run off has a small input) Close to a 100% of the grip in the rear is available to move the car forward. as you start to move the weight transfer to the rear increases grip. Regardless, you must know if you exceed the available grip the tires will spin.
Apply this principle while in motion. Any turn large or small will use some of the grip. So if your turn uses 30% of available grip, then only 70% is available to move the vehicle forward. Keep in mind that you dont have to be accelerating, even maintaining speed is done by applying tq to the wheels. Even on decel, you are using grip as the tires are caring tq back to the engine.
This may seem complex but its not if you think about it
if Grip used to thrust the vehicle + grip used to keep the rear end planted exceeds 100% of available grip the tires will spin. when the tires spin your available grip plumits only worsening a car, and essentially making the rear end practically float over the pavement. There are additional inputs such as the difference between potential and kinetic engery i.e. the amount of force required to start the rear end sliding (higher) vs the force to keep it sliding (lower)
Bottom line too much throttle (or a sudden strong throttle lift) will cause the rear end to break free.
Solution: Do some research so you get a better understanding of whats going on, and then modify your driving to solve your dilema (primarily your throttle input) because while your driving may not be the only input here, its the primary one.
/End book.

 

[MA70_Powa]

Yea I thought of that Moy, but as an experiment I've tried doing the same thing on the same corners/straights a few times at as close to the same conditions as possible and it doesn't happen all the time - sometimes I can hear/feel the tyres breaking traction but it doesnt kick its tail out.

and lewis, cheers for the theory behind it. but wouldnt that mean that if I was going around a left corner that the tail end would kick out to the right, as that'd be the side with the least grip? when it happens to me it kicks out to the left about 99% of the time no matter which way I'm going.

As I said above, I've experimented with the same pases on the same bits of road, and it doesnt happen every time. I can pretty much avoid it most of the time while daily driving, but sometimes it comes out of nowhere and freaks me out lol.

Oh, my shift times are quicker btw. It's true

 

[lewis15498]

Yea I thought of that Moy, but as an experiment I've tried doing the same thing on the same corners/straights a few times at as close to the same conditions as possible and it doesn't happen all the time - sometimes I can hear/feel the tyres breaking traction but it doesnt kick its tail out.

Things like temp, condition of payment, dirt or moisture on road can change the amount of available traction. Its your driving mate. I would suggest educating yourself on physics, and suspension dynamics if you want a better understanding. But you definitely need to modify your driving habbits. Based on moy's description of said shift kit, it sounds like this would worsen the problem. I would disengage/remove it until you get your driving worked out.

 

[Poodles]

Paging IJ...

Sounds to me like the cable adjustment...

 

[lewis15498]

Paging IJ...

Sounds to me like the cable adjustment...

Maybe I'm wrong, sounded like we were just talking about to much throttle. In which case i would have to be sorry I said it was your driving.

 

[jdub]

You could always go with a 3.9 LSD.

 

[IJ.]

Wow..... guys if you don't KNOW please don't offer advice really this thread is overflowing with dastoopid.... :nono:

Line pressure cable will only affect full throttle shift firmness, so unless you're Nailing it in bends that's not your issue.

Sounds like a tired LSD to me and it's just going open from time to time couple that with the shift kit and it will do what you describe.

 

[iwannadie]

Wider does not help with traction. Only contact path (deflate tires) and compound will achieve more grip.

Uhm, wider tire means more contact patch which means more rubber on the road which would give you more traction.

 

[IJ.]

Uhm, wider tire means more contact patch which means more rubber on the road which would give you more traction.

Very minimal effect in a straight line though you get more from a taller tire die to it's longer contact patch during acceleration when the sidewall deforms.

 

[MA70_Powa]

Yea guys it's not my driving habits, I've tried it under all sorts of conditions as I've said. And it's random.
Tired LSD sounds like it could be possible as I have nfi about the condition of mine.
No idea when the fluid was changed in it or anything

 

[gaboonviper85]

Sounds like you need to take it easy

 

[MA70_Powa]

omg stop telling me to change my driving habits people!
just because I say I'm 'on boost' doesnt mean im flooring it or speeding etc!
I get boost from 2000rpm, even with light throttle. this means a lot of my driving - normal and 'spirited' is within my boost range.

As I have said, this problem occurs randomly. It's even happened to me while going around 50kph and driving like a granny.

maybe I shouldve initially said 'while driving' rather than 'while on boost' ...