My 4L60E Transmission Journey

This section records my journey with the transmission in my 1993 Chevy C1500 Indy Pace Truck. When I purchased it, it had the original GM 4L60E automatic transmission in it. The 4L60E is the electronically controlled evolution of the original 1982 Turbo-Hydramatic 700R4. The TH700R4 was renamed “4L60” following the new GM naming convention when the electronic version, 4L60E, was phased in as the 4L60 was being phased out. This happened in 1993 for trucks (mine), vans, and SUVs, and 1994 for rear wheel drive passenger cars. 

I do not know if this 4L60E had ever been rebuilt before I purchased it.

Sometime in late 2014, I starting out on a road trip to Florida hauling my 2008 Triumph Bonneville, when the 3-4 gears went out. I learned from subsequent research and talking to my local mechanic that this is a common occurrence with this particular model transmission. So, I had a local transmission shop that my mechanic recommended,”rebuild” the trans and to “beef up” its performance in the process.

That 4L60E rebuild lasted maybe 10,000 miles of normal driving before it failed again in 2017. So, the next rebuild was done by a different transmission shop recommended by another mechanic that I had found in the new town where I had moved. This time, I had them install a TransGo shift kit and to change the shifting to be quicker, with less slippage.

That rebuild lasted maybe another 10,000 to 15,000 miles before it failed again… on June 18, 2020, the very day that I was able to test drive the truck with the newly rebuilt and replaced Blueprint Engines 383 Stroker in it. This time it was not only the 3-4 gears, but also the trans would just spin in “D” and would not move forward unless I put it in “D1”, then shifted manually to “D2”. When I got the truck back to Dave’s Auto Service, and discussed what happened with Paul, the Chief Tech, he knew exactly what had happened. His diagnosis was confirmed when he had pulled the trans and opened it up – the input sprag had failed.

input-sprag-fail

Input sprag in pieces

4l60e-transmission

The 4L60E transmission ready for tear down

clutch-plates

Several of the clutch plates show signs of wear

June 24, 2020

I authorized Dave’s Auto to go ahead with a complete rebuild of this trans, hoping that the third time will be done right. Based on the quality of work Paul did on the 383 Stroker engine, I trust that this will be the case. Parts were ordered and as soon as they all arrive, the trans will be rebuilt and upgraded to include

  • A heavier duty shift kit
  • A Corvette servo
  • New clutch plates
  • New solenoid
  • Wider band
  • Higher stall torque converter

Paul (Dave’s Auto Service) has guaranteed that the rebuilt and upgraded 4L60E trans will be more than able to handle the 363 HP and 437 ft.lbs. of torque of the Blueprint Engines 383 Stroker.

new-servo-billet-cover

New Corvette servo and billet cover

4L60E-trans-painted

4L60E transmission rebuilt, painted and ready to be re-installed.

new-4l60e-parts

New 4L60E parts begin to arrive

4l60e-servo-installed

New Corvette billet servo installed

band-comparison

New band is significantly wider than the original

4l60e-valve-body-mods

Valve body shift kit mods being done