Hard shifting with tune

[06MonteSS]

nope... the tunes are exactly the same... they're identical, so there are no tune issues....

has to be a mechanical issue somewhere...

[Ill_Born_SS]

Lew,Thanks for the info!
For me its when I install the 93 no DoD or 93 tune, It throws three codes in the 700 series (tranny) before I even get to the highway 3kms and if I reset the codes and try from there I get shudder followed by the codes again.
Does not happen with any other tune.
What could be different for the 93 tunes?

[06MonteSS]

really????? you too????? interesting... maybe your guys' trannies are on their way out and can't handle the extra torque being put to them... heh..

93 No DOD tune is the only one I've ever used, and have had no issues ever in the past 3 years since I've had it in there...

as far as I know, the only thing different in the 93 tunes is some additional/higher timing...

I will compare it to a 91 tune when I get home tonight and see if there are any other differences and letcha know....

[Ill_Born_SS]

First tranny did it , had gm hand rebuild no fault found. Then had the tranny built/ modified, guarenteed 600hp, many extras. With the stock tune or the 91 no DoD can break the tires loose at 80 kmph, no shudder or vibration. Only with 93 no DoD.
Have not tried it with Dod tunes due to the surging previously encountered, besides don`t want DoD.

Your help is most welcome,

[ffej0127]

Just a quick update (if thats what you want to call it!), just got back from the dealer and basiclly they told me its nothing. I took your advise Lew and told them i went to auto zone and had the code read (P0700) and they looked it up and told me that all it really is, is that the tcm is communicating with the ecm and its telling it to put the engine light on because there might be a problem, and after so many seconds and turns of the key if no problem is dectected with the car the light goes off and the computer resets.

So my car does this it goes off and my problem goes away for a while. But on the way home it started shifting hard again but no light came on, so i tried something, i pluged in the tuner and checked for a code and nothing was there, so i selected clear codes anyway, and just like that no more hard shifting.

So basicly im stuck with it unless the light stays on for a while and then they can plug in to see if there is a problem or not. but they seem to think its just a computer glitch like a loose wire or a ground possibly a bad tcm but again can not tell that if there is no code present. But they said its not mechanical which i guess is a good thing.

So maybe ill just get the tcm reflashed or try to buy a new one all together.
Also he also said that sometimes that when this happens the computer will increase the pressure in the lines resulting in firmer shifts.

[Ill_Born_SS]

Hey guys

I spent all nite on a dyno trying to figure this out.
It is not the tcm module, is not the wiring, not the ground!

With my stock tune and the 91 no DoD tune I am under 325 ft lbs of tq at the wheels, with the 93 no DoD I am over it.

As Lew said "there must be something mechanical" he is correct!

The 06 LS4 has a 6 bolt flex plate and later models have a 8 bolt.

As it turns out the flex plate is flexing just enough to allow a small amount of air to pass into the tranny fluid, thus causing the shudder and hard shifts at times due to a computer call for higher pressure.

I had the tranny completely done and even the tq con. cut open and furnace brazed but I reinstalled it to the stock flex plate not knowing this was happening.

To change the flex plate with the 8 bolt design I would also have to change the crank and do not know if it will cure the problem.

There is another option and that is to change the tq with the smaller (245mm) and lighter one from:

http://www.transmissioncenter.net/alto_2.htm

Anyhow, I got to get some rest and then do somemore homework!

[06MonteSS]

wow, good info Ill!!

wonder why more of them aren't doing it then.. you guys are the first two I've ever heard of having this issue....

I've got just over 68,000 miles on mine, and mine doesn't do that at all....


and 325 ft/lb's tq at the wheels??? stock is 323 at the crank... figuring 15% drivetrain loss, that's about 275 ft/lb's to the wheels... which is what I've seen on other's dyno sheets...

interesting...


you get a HP number while you were on there as well??

[Ill_Born_SS]

A little update, Flex plate was found to be cracked along three mount holes (eddy current).
While using the 91 tune there was little to no tip in KR, but with the 93 tune I was getting 3-6* tip in KR. This was just enough to give the whip effect to the flex plate and allow to air to be siphoned thru the input shaft, even though all the parts and seals were new. We repeated it many times to prove it the actual problem. Now on to bigger and better stuff.

Oh! Lew, and about the tq thing, my mods started at the heart of things and work outwards. 4.06x3.62,Ti rods, c/crank,fgdAl 10.5-1,and more to come.