The 4L60E is the latest in a long line of durable, high-function GM overdrive automatics that have come our way since the 1960s. The TH350 three-speed automatic had long been a mainstay with Chevy performance buffs, and GM followed that act with the overdrive automatic 700-R4 and 4L60 transmissions in the 1980s and 1990s. In the early 1990s, GM completely redesigned the 4L60 with an improved geartrain and electronic control, renaming it the 4L60E (with the E standing for electronic).
Because GM has always kept a sharp eye on improvement, the 4L60E has only gotten better with time, eventually becoming the 4L65E. Eventually the torque capacity was raised even more, netting the 4L65E a new name: 4L75E. The 4L75E is a specification you can build into your 4L60E/4L65E with parts or a complete build from Performance Automatic. The 4L75E is all about improved torque capacity and it can withstand greater amounts of horsepower, torque, and load than the 4L60E it replaces. This is good news for those of you building more powerful LS and small-block V-8s who don’t want the weight penalty of a much larger 4L80E.
1. We’re working with a 1996-up 4L60E transmission with a bolt-on bellhousing. This isn’t the newer, and improved, 4L60E/4L65E case with the widely spaced cooler lines, which would be the better option if you had a choice. We’re going to take this 4L60E and give it the greater torque capacity of a 4L75E.
2. To look at all of this is a bit intimidating for the average enthusiast. Fortunately, Performance Automatic does this every day so this large array of parts is no problem.
3. If you’re amassing parts for your 4L60E build, opt for the sun shell on the right from Performance Automatic. This is a thicker, stronger shell with a hub that can take large amounts of torque and not break. The sun shell takes a lot of abuse, so when you’re doing a trans rebuild always get the strongest one you can find.
4. Performance Automatic also steps up to this 39-element sprag for greater holding power in its 4L60E builds.
5. On the left are the stock clutch plates, also called “steels,” next to the heat-treated, high-performance steels from Performance Automatic. No matter what you intend to do with your 4L60E, toss the existing clutch steels and go with new, high-performance frictions like the ones from Raybestos.
6. Torrington bearings reduce friction and improve clearances in the 4L60E. These guys are a stunning improvement over stock thrusts because they reduce heat and free up power. The benefit of more power is obvious, but heat can kill a transmission so anything to help mitigate this is a huge plus.
7. The 4L60E/4L75E has an anti-chatter clip like this to absorb geartrain movement during the shift process. This is one item you do not want to miss during assembly because if you do you will get an annoying “clunk” during shifts.
8. The five-pinion front planetary yields greater torque capacity than the 4L60E’s four-pinion planet and ring gear. This is one of the times where more really is better.
9. On the left are the factory clutch steels. On the right are Stage-1 high-performance frictions and steels, which stand up to the increased torque expected with a 4L75E build.
10. The Raybestos Stage-1 frictions and steels are used in the forward clutch for solid engagement without slippage. Slippage generates heat, and as we said heat kills transmissions.
11. The reverse input drum is assembled with another set of Stage-1 clutches and plates. The plates are heat-treated and engineered to remain consistent under high-horsepower and torque application.
12. We’re asked from time to time what these three pressed-in inserts are. Performance Automatic provided the answer. The input shaft is drilled with hydraulic passages for both pressure and lubrication. When the machining is complete, these inserts are installed to close off the drilled passages. So, the simple answer is that they’re plugs.
13. As the clutch packs are completed at Performance Automatic clutch function is checked with compressed air. The telltale click indicates clutch piston function.
14. The input geartrain is then assembled and readied for installation into the case.
15. The 2-4 servo gets a specialized treatment to improve pressure on the low-reverse band.
16. The manual 1-2 band is installed once the input geartrain is in place. There are a lot of parts inside a modern automatic transmission, so experience here really helps.
17. The front pump assembly is then installed and seated. Each 4L60E/4L75E pump is blueprinted and fitted with new components to improve durability and pressure.
18. The accumulator, which stores line pressure, is fitted with a new piston and seals.
19. The stock accumulator spring (left) is replaced with one from Performance Automatic. This new spring, which helps firm up shifts, is included in the rebuild kit and complete transmission builds.
20. The accumulator cover is then installed along with new springs.
21. The completed 4L60E/4L75E valvebody is now ready for installation. The valvebody has been rebuilt and upgraded with a Performance Automatic shift improvement kit along with shift and pressure control solenoids.
22. The modified separator plate and valvebody gasket are properly mated together, making sure all the holes line up. At this time the control harness is also installed.
23. The completed valvebody is installed and all of the electrical connections are secured. There are no unimportant connections, so attention to detail is critical. Shift solenoids and sensors all must be connected for proper function. Manual shift remains manual shift on these electronically controlled GM automatics.
24. The rebuilt 4L60E, now a stronger 4L75E, is complete and ready for customer shipment. Each Performance Automatic build is dyno-tested before it leaves the facility.
Photography by Jim Smart