Hi everyone.

I wonder if you all have that weird tranny behaviour that i have
Note : It was chasing me even when the transmission was completely stock. (Now i have fully modified the bottom end)

Long story short, the tranny does not hold the gear. It releases it with throttle.

It happens to me the most when i go slowly uphill, around 10-30 mph, Second gear but in D position (It happens in 3 selector position too), When i release the throttle to slow down, and then apply light throttle again, without a complete stop, i feel like my transmission bangs into that second gear again. I can definitely feel it re-engages. It follows with a sound of clutches like you shake your 3-4 drum in your hand but once. It drives me nuts and i have a feeling im driving some old car.

I have a feeling that when i release the throttle, the gear disengage completely. Is that normal? Something i can do with it?

Thanks guys.

 

Hows the condition of your fluid and filter?

 

Hi Ryan?
Thanks for visiting.

Its brand new. Not a long time ago i upgraded and cured internal leaks in my original valve body.

It was like that when it was stock too with old filter and fluid.
Nothing changed.

 

Do you have any misfires or trouble codes present? do you have software like hp tuners?

 

When you release the throttle in OD or D position in the 4L60E the sprag overruns or free wheels. Like a ten speed bike when you stop peddling it just neutral like freewheels along with the fact you have probably shifted to at least 3rd possible 4th gear, when you come back in you get two things happening a downshift back to second in the conditions you describe and a catchup (spool up) of the input sprag which will feel like a clunck grab back into gear. It is normal in the stock overun set up valve body as the overrun clutch is off in all but actual 3rd gear d3 in the 60e (THE ATSG MANUAL IS WRONG AS IT SHOWS IT ON IN ALL GEARS D 1-2 3) and the feeling compounded by larger servos bands, pressures and feed hole sizes.

This is somewhat solved with the Sonnax HD 2-3 valve in the D3 (IT DOES KEEP THE OVERUN CLUTCH ON IN D1 D2 D3 POSITIONS) position though it won't hide the downshift back to second and can also be addressed again to some extent by routing the overrun clutch to stay on in D4 1-2-3 with additional VB mods , However this is also a trade off as you will then feel a distinctive downshift clunk as the trans downshifts to second coming to a stop though this too can be mitigated in the tune to make it less annoying.

In summary though due to the nature of the 4l60e and particularly when the stock feed sizes , servo sizes, feed holes and accumulators along with tuning is altered this somewhat clunky feel in the conditions you mention is just nature of the beast as they say, In fact if you look at the stock tuning tables with pull backs and shift timing GM went to great efforts to hide or lessen the effect even with the stock VB configuration, however these measures at the same time are not necessarily great for performance and durability.

 

Absolutely not. I did everything to make my spark and ignition work like i injected Testosterone in it.
I use the best Spark plugs wich are NGK Ruthenium and coils for my 4.2l 2008 Trailblazer.

No missfires occur ever.

I do have HPTuners

 

Hi Mr. Frank!

The mod i did is :

1-2 - .074
2-3 - .135
3-2 - .135-.
3-4 - .110
BR - .101
FwD Clutch -stock
Lo/Rev - .Stock
Rev - stock

-Block 3-2 Valves inboard
-Use the spring of 3-2 white spring into AFL Valve inside the current spring
-Block the 4th acum feed hole and keep the guts out
-Remove the Case Checkball
-Keeping the stock .471" boost valve because i cant change it.(ISS)

Installed the following :
-Sonnax 2nd and 4th super servos with 0.60" travel
-New 1-2 piston (I have the tranny with 1 spring only)
-Sonnax pinless FWD piston
-O ringed end plug
-Directionall superior capsule for 3rd.
-Reverse and FWD Abuse plugs
-New separator plate with steel checkballs
-FitzAll TCC Isolator for Canbus-Oversized AFL Valve from Central Valve bodies and theyr oversized end plug.

Note : Stock 471 boost valve.

 

With those Mods as I stated the feeling you get under the conditions of the description you give are pretty normal. You may be able to mitigate some in tuning. Normally I would say Try increasing the 3-2 solenoid duty cycle to try and mitigate but with the 3-2 valve blocked the 3-2 downshift solenoid does not do anything, You could play around with the upshift downshift tables under those conditions or even pressure tables (not suggested) but sounds like its a nature of the beast kind of situation.
The 4L60E can be a be a great Performance Trans however most of the mods to make it hold up also have some unintended consequences of feeling / drivability issues. As I said even looking at the tables in the tune at those conditions you will see what all they did with the pressure tables etc. to mitigate it even with all stock setup.
Frank

 

Sounds like Line-Pressure is pegging when you experience the kick-in-the-seat feeling.

Confirm with a Gauge to start out.