2008 5.3 4l60e 3.73 gears 180,000 miles lifted about 3 inches with 32 inch Ko2 tires
Hello gentlemen,
When I purchased the Blackbear tune for my motor and trans I was very unsatisfied with the transmission performance and I went back and forth with Justin and loaded a few different tunes he sent me but ultimately I was never happy with the trans but I didn't want to put it on blackbear, they said the trans is probably worn. The trans is old but still works great so I didn't want to push the issue.
Problems I had with the blackbear trans tune: harsh 1-2 shift until warmed up, very short 2-3 (happened very soon and didn't feel like it is in sync with engine speed), and 3-2 downshift flare (RPMs will raise high and then the gear engages and RPM drop back down as it goes into gear. almost like dumping the clutch, feels very concerning)
I will say that these problems probably existed before the trans tune but were amplified by the tune bringing them to my attention or were masked by factory trans tuning.
To solve the short 2nd gear problem I asked Justin to extend the duration of the 2nd gear but this basically got rid of 4th gear for me, my truck would go from 1st, 2nd, to 3rd to overdrive and only hit 4th gear under certain situations, I only ran it like this shortly before deciding this isn't a good solution and reverted back to stock trans tune in 2022.
This spring 2023 I reinstalled the first trans tune from Blackbear and have found parts of it enjoyable but the passing aspect when going uphill or passing on the freeway when I need that 3-2 downshift really is a problem.
This morning I came across this post that outlines someone else journey in solving this same problem:
https://ls1tech.com/forums/automati...2-downshift-flare-any-4l60e-experts-here.html
Here is an album the poster made that includes the original problem, some servo testing and then another video explaining their fix and showing the results:
https://photos.google.com/share/AF1...?key=MTh2MjR3bmQzY3o0RHlYRS1YSGUyallEQnAtZVB3
All this being said, it seems that the fix is to extend the length of the servo pin by welding a bead to the tip. This helps tighten the 2-4 band in turn eliminating the 3-2 dpwnshift flare.
Now my question is what do I do? I don't weld, is there a longer aftermarket servo pin I should use? Would a corvette server work? Do I get an extended servo pin AND a corvette servo? Can I run a corvette servo and trans tune at the same time?
- Signed by a man looking to milk every mile out of this transmission while drinking a lot of coffee this morning.
Dustin,
Drop the pan and check your 2-4 band clearance by moving it back and forwards using a flat blade screwdriver. You should see no more than 1/8" travel. If it's more than that you'll need to remove the servo assembly and look at the end of the apply pin. GM produced four different apply pin lengths to my knowledge.
There should be either no grooves, one groove, two groves or three grooves. The more groves you see, the shorter the pin is.
Based on your band clearance and pin size (assuming you have too much travel, e.g. too much clearance) you can do one of two things:
1. Locate a longer pin and install it in place of your current pin
2. Install a Transgo shift kit that includes a gold-colored shim that will take up the excess travel by physically moving the 2nd gear assembly and pin appx .100 closer to the band anchor location, taking up the excess slack
Shift flares in these transmissions are usually caused by
> excessive band clearance
> worn servo sealing rings
> excessive 3-4 clutch pack clearance (as the 3-4 pack wears, the clearance increases and the timing of apply and release between the band and 3-4 pack becomes out of synch)
> check balls stuck in the separator plate (see
@dkad260 's post above)
- The 1-2 check ball wears the plate and get's stuck much more so than the others
- Inbalance between hole sizes for the 2-3 shift feed port and 3-2 exhaust port in the separator plate (seen only after rebuilds and the builder drills one out but not the other)
Servo Info:
The 700R4 and 4L60E servo assembly consists of two different servo pistons: one for second gear and one for fourth gear.
There were three different 2nd gear servos that are commonly found in the 4L60E, they are typically identified by the last three digits of their respective part numbers. I put them in order of their respective apply surface areas (the more apply area, the stronger the hold on the band, all other things equal):
- "554" - installed in lighter duty applications w/v6 engines
- "553" - installed in the majority of v8 applications
- "093" - known as the 'corvette' servo, installed in vettes, f-bodies and some sub-models of Escalade, Yukons and pick ups
This picture shows the 553 servo on the left and the 093 servo on the right - the 093 servo has appx 10-13% more apply surface area and if substituted for the 553 servo will firm up the 1-2 shift slightly. A sonnax super hold 2nd gear servo will firm up shifts more than the GM vette servo. Note the grooves on the end of the pin. Two-groove pins are the most common and likely what you have.
The fourth gear servo piston is inside the cover and the same servo piston was installed in all models. Install a billet forth gear servo piston kit if you need more holding power in overdrive.
My recommendations
Put your truck up on all four jack stands (or at least the rear wheels), put it in neutral and then,
1. Drop the pan and check band clearance - this will also allow you to view the pan and determine if the trans needs to come out for a complete rebuild or if installing a shift kit and tightening up band clearance will suffice
2. If band clearance is too high, install the Transgo SK4L60E shift kit along with new valve body gaskets (use the orange stripe gaskets) - that should fix your clearance problem (and possibly others as well)
> follow the step by step instructions provided in the kit
> If your spacer plate has check ball locations that are excessively worn, install Fitzall's repair sleeve kit (this is a separate kit from the Transgo kit) - otherwise you should not have to replace it
> Install new shift solenoids and a new electronic pressure control solenoid (all of these are on the valve body which you will have on the bench to install the shift kit)
3. Reinstall the servo assembly after you have installed the shift kit parts but BEFORE you reinstall the valve body
> Air check the servo's operation by introducing compressed air into the two feed port locations (see pic below) - fourth gear port is on the pan rail and 2nd gear is between the worm tracks
4. Once you have validated the servo functions and applies the band upon air check, measure clearance again - should be 1/8" or so; spin your drive shaft to confirm it's not binding
5. Reinstall the valve body - tighten all bolts to 104 inch lbs - make sure the long 8mm bolts go back into the exact same holes that they came out of - if not, their added length will interfere with and lock up the sun shell (or not go all the way in depending on where you try to install them)
6. Install a new filter, pan gasket and pan (don't forget your magnet) - Torque all pan bolts to 98" lbs
7. Restore the factory transmission tune and take it for a test drive
If band clearance is acceptable upon initial inspection, follow steps 2-7 anyway as likely your servo sealing rings are worn and fluid is being allow to bypass - other components (acc springs, plate, solenoids, etc are also worn)
I have a few 4L60E videos you can refer to for guidance:
>
Valve body reassembly (simply swap the shift kit parts in place of the factory parts, following the instructions in the kit)
>
Servo Assembly (skip to 49:00 for the servo)
>
Final assembly (skip to 5:00 for the air check procedure)
If i think of anything else, ill edit the post.
