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2,476 Posts
Discussion Starter · #1 ·
The big problem with these 4L60Es is that the torque convertor never really hooks up nor totally releases 100%. There's always some slipping going on to make the shifts smooth and not very noticeable to the general public.

Therein lies the problem of overheating when we/you tow something and no external cooler is going to make much difference in overall life to the unit because it is cooking itself on the inside.

The life of the TCC is shortened - but the fluid is cooked as it comes boiling off the clutch in the convertor.

The clutch material itself is Kevlar® and it can take a lot of abuse - up to a point.

I'd been feeling the TCC in my 2005 TB/EXT getting weaker and weaker so I decided to get it rebuilt before I lost 3rd (Direct) gear altogether.

If it's not time to rebuild your transmission, then I suggest that instead of trying to drop kick an aftermarket cooling radiator in the transmission cooler circuit, that you eliminate the problem itself - the TCC slipping.

Now --- I'm gonna pimp for an old fried of mine from many years ago. Although he personally has passed away, the company thrives on with new products and improvements to modern transmissions as they need help to not only make them well again, but to make them stand up and bark!

Gil Younger makes a "Shift Kit®" (that term: "Shift Kit" is his registered trademark and is not legally used by any other shift improvement kits on the market) that is - if not thorough - it's somewhat capable of taking your stock slipping unit into a next-to-manual-shifting fire breathing transmission.

There are varied levels of performance and I had the HD-2 unit added to my transmission ...............

Font Auto part Electric blue Rectangle Brand

{cont'd}.............. that will solve that problem and when it finally turns out that you need to finally go into the unit for a full rebuild, then finish the installation at that time.

Actually ---> you can put a lot of the kit into the transmission while it's in the car - except for drilling the front return circuit and putting an improved front seal and keeper on that seal without removing the unit anyway.

Manufacturer's notes:
(The above) 4L60E-HD2 Reprogramming Kit fits 1993 to 2015 General Motors vehicles equipped with the 4L60E, 4L65E and 4L70E automatic transmission.
NOTE --> Common complaints on this transmission are TCC slip or shudder, code P1870 or P0894, harsh 1-2 shift, double bump shifts, 2-3 flare up, burnt 3-4 clutch plates as well as inconsistent pressure boost problems.​

√ The torque converter clutch regulator valve bore is very prone to wear causing the TCC slip complaints and related code.
√ The TCC slip code leads to the harsh 1-2 upshift as the ECM recognized the TCC slip and commands high line pressure to avoid further TCC slippage and damage.
√ The 3-4 clutch plate failure as well as the 2-3 flare up complaints are caused by an inconsistent pressure boost and poor overall calibration of the shift accumulation system.

  • TCC slip or shudder
  • Code P1870 and P0894
  • Harsh 1-2 shift
  • Long soft shifts
  • Double bump or slide bump on the 1-2 shift
  • 2-3 flare up
  • 2-4 band failure
  • Burnt 3-4 clutch plates
  • Burnt forward and low/reverse clutch plates
  • Pump slide and valve bore wear
  • Second servo piston spring, two shims and two O-rings
  • (2) 1-2 accumulator springs, spring seat and three spacers
  • 3-2 Downshift valve spring
  • Actuator feed limit valve spring
  • (2) 1-2 accumulator valve springs
  • USA-made hardened steel 1-2 shift valve and spacer
  • Low valve spring
  • USA-made hardened TCC regulator and isolator valve, spring and installation bolt
  • (2) Pressure regulator valve springs and spacer
  • .500” boost valve, bushing and snap ring
  • EPC screen wire spacer and oversized 1-2 checkball
  • (2) Drill bits
  • (2) Reverse input piston orifice cup plugs
  • 3-4 accumulator spring
  • (2) Valve body gaskets
  • Pan gasket
  • 3-4 clutch return springs and orifice capsule
  • Forward clutch return springs and installation washer

2,476 Posts
Discussion Starter · #3 ·
The Transco 4L60 / HD-2 is right at $100.00, depending on provider.

Some of the kit can only be installed during complete teardown.

2003 Chevy Trailblazer LT
393 Posts
What is the valve body mod ? Im hoping I can get a few more years out of it before it needs a rebuild. I still need a passanger door. That rust is gonna keep getting worse.
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