So other than my LS2 project truck I have a 2009 Colorado ZQ8 with a 4L60E. It was miserable to drive stock so after a tune from Blackbear Performance about 20k miles ago it really woke up the response and power. After driving it faster than the average guy the shifts are starting to take a bit longer. I can only assume this is due to clutch wear and therefore a longer shift interval due to increased travel. Whats my best option? have the extended warranty (and the bone stock ECU/TCU) and could have the dealer look at it or I have thought about upgraded parts. Anyone have any feedback? thanks

 

I would start with just a boost valve to raise all-around line pressure. The Sonnax 4L60E-LB2 (note the "2" !) costs under $30 and after dropping the pan takes barely 5 minutes to install. Any trans shop can order it from their distributor and hopefully not charge you more than 1 hour labor. I probably have documented the exact steps sometime on this forum.

The TCU could be tuned for somewhat tighter shifts too.

If that doesn't do enough, I would next install the Transgo HD2 shift kit ($80). That requires dropping the valve body which might be outside your comfort zone; probably 3 hours labor at a trans shop. (It also comes with a boost valve, but skip that step if you have the Sonnax installed; Transgo boost valve instructions are wrong for your year anyway.) It is best to remove the Servo to install the HD2 parts for it. At that point you should ensure you have the Corvette servo for the 2nd gear piston. (Only $15). Or install the Sonnax Billet 2nd gear servo. ($80).

I suspect you actually have a 4L65E which has the better 7 friction 3-4 clutch. By that year the sun shell is hardened, the sprag reinforced and other improvements made. Hopefully the trans will not need to be pulled and rebuilt for quite a while.
(BTW - I bought a brand new '09 4L60E and had to mod it to work with a '02 PCM. Later I rebuilt it with $3K in aftermarket parts such as billet shafts, close-ratio planet, etc.)

Is that the kind of info you are looking for?

 

This guy^ Mrvedit knows his stuff! Lol

 

The Delphi EPC solenoids in the late model 4L60E/4L65E transmissions are notorious for sticking after they age a bit. They tend to stick in the low line pressure position and then unstick suddenly. This will give you a very sloppy, kind of "slide" shift, usually with a thump at the end when the solenoid unsticks and the line pressure corrects suddenly. They are not that expensive and easy to replace.

I had a 2005 GMC Envoy just this week that was in for a complete build because he was told by the "five letter" transmission shop that he needed one. He was very pleasantly surprised when, after a routine service and a new EPC solenoid, he was good to go...

 

Very good info guys. Since I am still under warranty I worry about aftermarket parts and the dealer wanting to not cover related items. Is clutch wear what I am experiencing? The shifts just seem longer, especially 1-2. but 2-3 is almost the same. Occasionally i get a shift that seems to hang up and shift at a higher RPM than normal for a given throttle application. That never happens more than 10 minutes after startup. I'm thinking I'll put the oe ECU/TCU back in and see what the dealer says. If they don't think the longer shifts don't require repair I will look into the aftermarket parts.

Questions:
Can I order the Sonnax 4L60E-LB2 online somewhere?

Also, on the shift kit, Summit lists the kit for a 4L60E from 1993 through 2009. Does that kit also work on the 4L65E? Dropping the pan and the valve body aren't out of my comfort zone. It also lists that you can hold 1st, second and 3rd to any speed. OE 1st stays in 1st but if you select 2nd it starts in second and holds. Does the shift kit negate the 2nd gear start?

Thanks for the help guys.

 

First, I doubt any dealer mechanic would notice the bigger boost valve; also you could easily put the old one back in.

The 1-2 shift does not engage a clutch - it engages the band which is controlled by the 2nd gear piston in the servo. I suppose the band could be wearing already. The HD2 kit includes a special servo cover shim that might tighten that up.

"That never happens more than 10 minutes after startup" - You should not worry about small things before the engine/trans is fully warmed up.

You can order the Sonnax boost valve here:

http://hptransparts.com/general-moto...g-kit-509.html

Or here:

http://www.transmissionpartsusa.com/...-04l60elb2.htm

Since shipping is about $10, the total would be close to $40. Try a local trans shop or ebay too.

The Transgo HD2 kit will indeed fit all years of 4L60E, but you have to be careful with the boost valve. The (skimpy) instructions show using a thick aluminum spacer with the boost valve. The '96' through '05 use a taller boost valve, and that spacer is then critical (or line pressure will be too low). However, around '06 GM changed the pump design and went with a shorter boost valve; it is then important NOT to use the spacer or line pressure will be sky high.
(?? Pre '95 4L60E may have had a shorter boost valve too. ??)

The Sonnax instruction for their boost valve show this difference:
http://www.sonnax.com/system/instruc...LB1-LB2-IN.pdf

I would recommend the Sonnax boost valve over the HD2 one anyway because it includes o-rings for a tigher seal and therefore better pressure control.

Personally I have always left the Transgo "hold any gear" valve out as I have no desire to overrev my engine and I can tune my exact shift points. Putting the shifter in D2 will still give you a 2nd gear start if your PCM does that now.

 

Great info. Based on reading the Sonax install sheet it looks like the booster goes into the pump but instead of removing the pump through the bell housing it is accessed from the side of the pump through the pan opening? It also looks like they have a recommendation chart for orifice feed hole enlargement. Do you suggest simply installing the booster valve and not enlarging any orifices?

Thanks again.

 

You only have to drop the pan and filter to change the boost valve. You need a pair of snap ring pliers. Have a good light to make sure the snap rign goes back in properly.

I would start with just the boost valve. Enlarging orifices requires dropping the valve body as which point you are basically installing a shift kit. You might want to wait until your trans warranty is expired.

 

While a larger boost valve is definitely a good modification, you can put all the boost valves in it that you want and it's not going to fix your failed EPC solenoid.

You're getting noticeably longer and softer 1-2 shifts. Even if your band had worn to the point of having a larger than ideal amount of servo travel, as long as you had proper line pressure control, you would actually feel your 2-3 shift getting sloppy due to the excessive servo travel, and not your 1-2. In fact, in many cases, you will actually feel the 1-2 beginning to become harsher as the PCM ramps up the pressure in an effort to bring the shift times in line, compensating for the longer servo travel.

But, you have a line pressure control problem...

Also, FWIW, "shift kitting" a 4L60E is very easy and does not require a "shift kit". I build more than 200 4L60E's every year and haven't used a "shift kit" in years... With the proper parts used in the build, proper servo and 3-4 clutch clearances, some orifice sizing and some accumulator mods and you're there!

 

As I understand it, Dynamic396 believes that you might have a bad EPC solenoid. Therefore you might as well replace that too if/when you install a bigger boost valve. It is also easy to replace, just a single 8mm bolt holds it to the valve body. (Correction: You also have to remove the 1-2 accumulator - 3x 10mm bolts). Be sure to get a late model one as early model ones had a different electrical connector.

Dynamic396: I've been suspicious of it, but some people "adjust" their EPC by 1/4 turn to increase line pressure across the board. Kind of a poor man's "tune". What are your thoughts and might it be useful for the OP?

 

You'll also have to pull the 1-2 accumulator to get the solenoid out of the valve body. Replace it with the late model Borg Warner solenoid.

While you can adjust the screw on the EPC solenoid and change the range in which the solenoid regulates by a little bit, I don't do anything with them. I prefer to make any pressure adjustments at the regulator valve (PR springs, boost valve, etc.).

 

Oops, I keep forgetting that in my posts. I corrected it above.
Glad someone is keeping an eye on me. Thanks.