I did a search and it seems it is a 50/50 on where to do a trans go shift kit or get a tuner and mod the auto trans that way.

My car has 81K miles and not sure if tranny has ever been serviced so kind of seeing what other people think about which mod to do. If I get the transmission serviced might do the shift kit but if the most of you say it is a waste of money will put it to a tuner

Thanks

 

following

 

As a tuner----My experience is that it is not a good idea to put a shift kit in any computer controlled trans---Yes you can make some part swaps like a better servo but never a full shift kit--
Any tuner can make a 4l60 trans shift aggressively with tuning---enough to bark the tires in 2nd gear--The stock trans tune is extremely mild when it comes to shift times--so there is lots of room to firm up the shifts---Not only the gear shifts but the converter lock/unlock speed and firmness as well--
A higher stall converter is the best mod you can ever do on any auto trans--and especially on a C5---it really wakes them up --almost tripling the TQ on a hard launch!!
Most shift kits increase line pressure--- and we were trained at EFILIVE that doing that is not the correct way to firm up shifts---But rather by quickening up the solenoids at a shift---Eliminating TQ management to get rid of delays and lowering the "shift time" tables---As an example the stock program commands like .50 second shift time---But tuners can easily cut those in 1/2 to a safe .25 second shift time----
Quickening up the shifts without increasing line pressure will make the trans clutches last longer so they don't slip and also reduce heat of the trans fluid---as soft lazy shifts make the trans temps go up-- and allow the clutches to slip somewhat to make the shifts seamless and extra smooth ----all bad for longevity and performance

 

I remember reading in a previous post this exact thing you posted thanks for posting it here for everyone to see. So then you recommend a HP tuner to mod the trans then?

 

Don't the RPM rebuilt transmissions include the TransGo kit as part of the rebuild?

 

More line pressure is the only way to make a 4L60e shift quicker. The shift solenoids are basically on-off devices and have no control over pressure or shift time. When it's time to shift, the PCM just turns a shift solenoid either on or off. there are 2 solenoids so the PCM follows a somewhat binary shift pattern as it goes through the gears.

During a shift, the PCM adaptive line pressure control routines attempt to make the shift time match what the table says as the shift is occurring. So, if the shift takes too long, the PCM will increase the line pressure the next time meaning that setting a shorter shift time will cause a higher line pressure.

 

Before "I/We" recommend that you GO in any one of several 4L60E improvement directions,,, we need to know some information:

- Year C5?

- Current engine /Drivetrain Modifications? Power Level?

- Desired and or future drive train modifications??

- WHAT ARE YOUR GOALS/NEEDS to modify the transmission?

- Budget


The 4L60E is a good all season transmission. It was designed to handle STOCK LS1 power levels in a wide range of uses. GM did a good job at PROTECTING the power train from sever abuse.

They added lots of:
- TORQUE MANAGEMENT (When you mash the accelerator to the floor, the PCM decides how much the throttle opens and how fast!) Trust me,,, it IS NOT what you think it is!!

- Delayed shift times

- Moderate line pressures

When you start removing all that protection, adding power and driving the car a LOT harder, BAD things start to happen.

The transmission runs a LOT hotter and starts to COOK internal parts (seals, bands and clutches) Weak parts in the transmission start to fail.

YES!! There are also some inherently WEAK links in the 4L60E:

Here is a small sampling of some You Tube Vids that explain what can and will BREAK!



Tuning is a MAJOR part of increasing the performance of the 4L60E. It is NOT the only part of the equation. Adding improved shift improvement hard parts, better servo pistons, performance clutches and bands, improved shells and planetary gears and better valve body parts is necessary for total transmission performance and life expectancy.

If and when you add a higher stall speed TC, you MUST add an external trans oil cooler to prevent transmission overheating. The C5 transmission programming is contained within the PCM.

Bill

 

Yes Bill, you can improve many parts but you don't put a shift kit in an "e" transmission to adjust the shift speeds when adaptive line pressure control is active. The adaptive line pressure control will see the transmission shift quicker and lower the pressure to make the shifts take the right amount of time which defeats the purpose.

 

RPM does install a TransGo in their units.

 

From TransGo site,

There are lots of things a kit can improve besides making hard shifts.

 

This is contrary to everything we were taught at EFILIVE training--Simply increasing line pressure will--Lose HP at low RPM's as the trans pump is trying to create too much pressure----Excessive line pressure is hard on your trans as well--seals will blow--
And finally NO the solenoids are not simply "on/off" they are all controlled by the ECM---The solenoid can snap slow or quick--The table in the FMC table is based on fluid temp and line pressure--For example at normal fluid temps the solenoids have a 1 second delay or "snapping time" --- as the line pressure goes up the snapping time goes down to like a .88 second time---- Shortening up the snapping time is the best way to get crisp shifts---Most tuners at WOT will reduce that time from a STOCK .88 to a far quicker and safer still .68---In the P/T areas it's best to subtract a % to the solenoid times---On a C5 a -15% is a good starting point--which is still safe and will result in quick crisp shifts-----

 

Saying you can shorten shift times or firm-up the shifts without a higher line pressure must have been the layman pseudo-explanation of how it works brought to you by some tuner who can understand the effect changing parameters has but doesn't have a clue how the transmission actually works. The explanation you just posted that was apparently taught to you in the school is complete and utter BS. It's a tech class so they should teach the correct thing, not some BS made up crap about how it works.

The shift solenoids simply switch on or off. The PCM control is limited to turning them on or off, nothing more. There is a small delay because anything mechanical takes some amount of time to move, but it's pretty much a fixed delay based on the characteristics of the solenoid and it happens much quicker than the total shift time. The tuning school story about the shift solenoids taking a variable time to switch or "snap" is complete BS.

The force motor solenoid is a completely different device than the shift solenoids. It is the main pressure controller on the output of the pump. The PCM uses a PWM signal with current feedback to control this solenoid which controls the line pressure. More current means less line pressure.

Once the solenoid switches, the line pressure still has to overcome clutch springs and accumulators before being able to apply the clutch and then the pressure in the clutch has to build enough that the clutch quits slipping and actually starts to hold the engine torque. All of this takes time to happen and is the real reason the shift takes the 0.88 seconds you describe, not because the shift solenoid takes 0.88 seconds to "snap".

So, to sum it up. The solenoid switches and then the line pressure engages a clutch or band. The higher the line pressure during the gear change, the quicker the clutch or band will overcome the engine torque and engage. That's the way it really is. There is no such thing as a faster shift without increased the line pressure.

The FMC table is not pressure vs temperature. Sadly, it sounds like they told you that that the 0-96 scale was pressure. It isn't. It's just an offset or think of it as percentage of pressure with 0 as the least pressure and 96 as the most pressure.

To be very basic. all of the PCM tables and calculations come up with a value representing the desired line pressure somewhere between 0 and 96. Then, there is a scalar that is typically called maximum pressure. It's function is to cap the value. Finally, the PCM takes the value and transmission temperature and looks up the current in the FMC table. If then applies the current to the force motor and whatever pressure results is a function of the mechanical operation of the pump and force motor when that current is applied to the force motor.

Now - shift time compensation. All this does is measure the time it takes for the shift to occur. The PCM does this by measuring the input vs output speeds of the transmission and decides that once the speeds have changed enough that the shift has completed. If the PCM sees the shift take too long or too short of a time, it will make a modification to the above pressure value for the next shift. This is why when you shorten the shift times that the transmission takes less time to shift and has a quicker firmer shift.

There are no tables in the tuning software that gives line pressure because the PCM does not know the line pressure or directly control line pressure. All the PCM knows is the force motor current, which it's in direct control of.

Also, the story about a higher line pressure blowing seals and causing damage isn't the whole story. The 4L60e can easily withstand up to about 230-250 psi of line pressure without damage. That type of pressure is the expected pressure at full-throttle. Making mechanical modifications to the transmission (at the line pressure controller or force motor solenoid) or adjusting the FMC table to have a lower current could increase this maximum pressure. No other table adjustments will cause the maximum line pressure to be higher.

 

Gotta agree with lionelhutz on this. Real reason you were taught to not tweak the line pressure values is because the PCM will adjust the line pressure trims to match the times and effectively undo your tuning change - unless you change the shift times. The two are related much as idle airflow and idle rpm values are related. If you just change the airflow the computer will apply idle trims to get the car to idle at the rpm value.

A shift kit can allow for faster times without increasing the line pressure due to changes in accumulator spring rates and opening up a bit some passages in the separator plate that are by design restrictive, but it too will be affected by the PCM adapting for the targeted shift times in the tune.