Fellow ISSF members, I finally have sufficient tools, experience and confidence to offer 4L60E valvebody and pump rebuilding services on a very limited basis.
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You probably can tell by my posts on this forum that I've been working on 4L60Es as a side hobby for about 20 years. Shortly after buying my first B-bodies in 2003, I ended up with two broken 4L60Es that summer, and apprenticed myself to a shop to learn how to rebuild them. This was three years before youtube, mind you; the only things available to the DIYer were ATSG manuals, the TransGo catalog, and kind transmission builders.
One year later, I thought I knew everything and could rebuild a 4L60E pretty quickly, but honestly I was pretty naive, and there was a lot of industry-wide unknown. Thanks to significant R&D by Sonnax, TransGo, and others, the key causes of 4L60E failure are now well-understood. After having built six 4L60Es since 2018, and invested hundreds into proper test and rebuild equipment, I am now convinced that valvebody wear (causing insufficient line pressure) is the number one root cause of 3-4 clutchpack failure.
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As a testament to this, summer 2023, I rebuilt the valvebody in my gold wagon with 155k on the stock LT1 and unrebuilt 4L60E, then road raced it over 300 miles (WOT 3000-5500 rpm sustained) and it still drives perfect. I've put 9000 miles on the car in the year I've owned it, driving it daily, and it just drives and shifts perfect. I drove it out to Topeka, KS for the 2023 ISSCA nats, drove it the full 20 minutes EVERY session, then drove home. That fall, my son and I drove it the full 25 minute sessions both days at Barber Motorsports park for two days straight. Then drove it home. UPDATE 2025 - drove it 1900 miles round trip to the 2024 ISSCA Nats, 134 miles on road course, drove it home no problems.
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Removing and reinstalling the valvebody is not for the novice, but if you are mechanically inclined, willing to learn and get your hands dirty, and push your transmission rebuild out a ways longer (or have these parts rebuilt while you rebuild the rest), this may benefit you. One thing I ALWAYS do is replace the Torque Converter Clutch (TCC) regulator valve with an oversized sleeved Sonnax 77754-04k valve which permanently fixes the lockup valve wear issue in the '95-up 4L60Es. It is the best solution, and allows the PCM to continue to control the apply rate so you can make the lockup as smooth or as firm as you want.
![Image]()
You probably can tell by my posts on this forum that I've been working on 4L60Es as a side hobby for about 20 years. Shortly after buying my first B-bodies in 2003, I ended up with two broken 4L60Es that summer, and apprenticed myself to a shop to learn how to rebuild them. This was three years before youtube, mind you; the only things available to the DIYer were ATSG manuals, the TransGo catalog, and kind transmission builders.
One year later, I thought I knew everything and could rebuild a 4L60E pretty quickly, but honestly I was pretty naive, and there was a lot of industry-wide unknown. Thanks to significant R&D by Sonnax, TransGo, and others, the key causes of 4L60E failure are now well-understood. After having built six 4L60Es since 2018, and invested hundreds into proper test and rebuild equipment, I am now convinced that valvebody wear (causing insufficient line pressure) is the number one root cause of 3-4 clutchpack failure.
As a testament to this, summer 2023, I rebuilt the valvebody in my gold wagon with 155k on the stock LT1 and unrebuilt 4L60E, then road raced it over 300 miles (WOT 3000-5500 rpm sustained) and it still drives perfect. I've put 9000 miles on the car in the year I've owned it, driving it daily, and it just drives and shifts perfect. I drove it out to Topeka, KS for the 2023 ISSCA nats, drove it the full 20 minutes EVERY session, then drove home. That fall, my son and I drove it the full 25 minute sessions both days at Barber Motorsports park for two days straight. Then drove it home. UPDATE 2025 - drove it 1900 miles round trip to the 2024 ISSCA Nats, 134 miles on road course, drove it home no problems.
Removing and reinstalling the valvebody is not for the novice, but if you are mechanically inclined, willing to learn and get your hands dirty, and push your transmission rebuild out a ways longer (or have these parts rebuilt while you rebuild the rest), this may benefit you. One thing I ALWAYS do is replace the Torque Converter Clutch (TCC) regulator valve with an oversized sleeved Sonnax 77754-04k valve which permanently fixes the lockup valve wear issue in the '95-up 4L60Es. It is the best solution, and allows the PCM to continue to control the apply rate so you can make the lockup as smooth or as firm as you want.
