Here is some information that I came across while looking through my numerous files about the 4L60E transmission. I don't recall the source, but for your viewing pleasure here it is:
Top 30 4L60E Problems
What is a 4L60E Transmission?
The 4L60-E is an automatic shift, four-speed overdrive, longitudinally positioned transmission. It has been considered to be the best rendition of the finest overdrive automatic transmission ever produced. The 4L60-E is found in nearly every GM rear-wheel-drive application, including the C/K Truck, Sonoma, Jimmy, Tahoe, Yukon, Astro, Safari, Suburban, Bravada, Firebird, Camaro and Corvette
Before the Late 4L60-E transmission, there was the Turbo 700R, which was introduced in 1982. The 4L60-E is GM's successful continuation of the ever-improving 700R4 (aka "4L60" since 1990), introduced in 1982. The 4L60-E is the "E"lectronically shift controlled version of the 4L60. The Late 4L60-E was released in 1997 in and fully phased into wide use through GM by 1998 in both RWD car platforms (including the C6 Corvette) and trucks in both 2wd and 4wd configurations. (Most transmission models are not distinctively noted with the "E" since all GM transmissions are now also controlled electronically.)
The 4L60E Transmission has went through many changes/improvements over the years since it first came out in 1982. From bells to valve bodies, added solenoids, changes in pump and convertors. The 4L60E transmission weighs 146 pounds dry, and 162 wet. It requires 8.4 quarts (9.64" torque converter) or 11.4 quarts (11.81" torque converter) of transmission fluid,
Top 30 Common 4L60E Transmission Problems and Repair
Below is a list of common transmission problems with the GM 4L60E Transmission and possible solutions to repair. Although you may have some of these symptoms / problems with your 4L60E Transmission, the repair solution may differ. This list is merely a guide to the possible solutions. For a complete diagnosis on your GM 4L60E Transmission problem, contact us for a Free Diagnostic.
1. Slow, slipping or no reverse: “lo-reverse” clutches are worn out, fluid leak in the reverse apply circuit, or broken sunshell. It is possible to remedy a fluid problem by removing the checkball from its cage in the case in the rear of the transmission may help (must remove valve body), or adding a high-viscosity additive or other seal restorer product. May also have worn boost valve (can replace in the pan).
2. 1-2 shift does not happen at WOT (Wide Open Throttle) until you let off the gas: Best case: try replacing the TPS. Middle case: leak in the 2nd gear apply circuit (servo assembly or 1-2 accumulator). Double check by using the pressure gauge and watch for a big drop when the PCM commands 2nd gear. Worst case: poor line pressure rise (see below).
3. 1-2 Shift shudder at WOT (Wide Open Throttle); delayed or abnormal 1-2 shift; There's a problem ONLY on the 1-2 shift: 1-2 accumulator piston cracked or stuck cocked in the bore. Check the yellow spring inside the accum housing for breakage. Also, if the accumulator housing walls are scored, the housing must be replaced.
4. 1-2 shift is delayed and harsh, may not shift into OD: TPS needs to be checked for smooth and linear electrical response over the entire range of motion. If not, this must be replaced.
5. Trans does not upshift out of first, speedometer reads zero at all times: Could be VSS failure. Rear of transmission needs to be fixed. Transmission needs to come out in order to access VSS.
6. No 3rd or 4th gear: “3-4” clutches are worn out: Needs to be removed and rebuilt. The car is safe to drive (in 2) until you can get it fixed.
7. Sudden grinding noise with no prior warning primarily in 2nd gear, behavior in reverse may be abnormal: sunshell is fractured. Must be removed and rebuilt. Try not to run or drive the car or further damage could result.
8. 1st and 3rd only, no 2,4 or R: Sunshell is fractured or splines are sheared off. Transmission must be removed and rebuilt. Try not to run or drive the car or further damage could result.
9. No 2nd or 4th gear. 2-4 band is slipping: Servo seals may be damaged. Otherwise, 2-4 band is worn out. Transmission must be removed and rebuilt.
10. Trans shifts into gear harshly, car feels sluggish off the line, No 1st, 4th or TCC lockup available, Manual 2nd, 3rd and Reverse are only available gears, CEL is on: transmission is either in limp-home mode or has lost electrical power. If there are lots of error codes in the PCM, check the underhood fuse that powers the transmission, and if it pops again, look for a short in that circuit like an O2 sensor harness touching exhaust. Otherwise, check PCM codes for a particular fault in the transmission causing the PCM to put it in limp-home mode.
11. No 1st or 4th available; trans shifts 2nd to 3rd by itself in D or OD and locks the converter: ShiftA solenoid failed Or a wiring problem from PCM to trans or PCM. Needs diagnostic testing.
12. Car goes into gear but feels very sluggish like the brakes are dragging, but it will roll easily (starts out in 4th gear), you manually shift to 2 to get it moving, once it's moving you put it back in OD and the car shifts 3rd to 4th on its own and locks the converter at the appropriate time: ShiftB solenoid failed: A wiring problem from PCM to transmission or PCM.
13. No TCC (Torque Converter Clutch) lockup: Brake pedal switches improperly adjusted (always on), TCC solenoid failed, TCC clutch worn out (must remove transmission and replace TC).
14. TCC (Torque Converter Clutch) always locked: TCC apply solenoid circuit shorted to ground, TCC solenoid blockage, or TC broken (must remove trans and replace TC).
15. Horrible noise in 4th and feels like the brakes are on: overrun clutches are applying due to a cracked or leaking forward piston. Overrun clutches will be worn out after 30 seconds of this behavior. Car can be safely driven in D. Transmission must be removed and rebuilt.
16. Soft shifting, gradual performance degradation: Poor line pressure rise due to leaking boost valve, clogged EPC filter screen, failing EPC solenoid, or worst case: leaky seals throughout. Seal restorer may fix last problem, but probably remove and rebuild needed.
17. No forward movement in OD or D, but L2, L1 and R work: Forward sprag is broken. Transmission must be removed and rebuilt. Try not to run or drive the car or further damage could result.
18. Extremely harsh shifts from P or N, normal shifts at WOT: EPC (Electronic Pressure Control) solenoid failed. Fix as soon as possible or hard parts will eventually break.
19. Loud bang, grinding sound, loss of all gears, and a binding driveshaft: Snapped output shaft. Try to wiggle driveshaft - if more than 0.020" play, that's the sign. Must be removed and transmission rebuilt.
20. Trans seems noisy when moving in 1st and Reverse, noise goes away instantly if you shift to N or the transmission goes into 3rd gear: Reaction planetary is worn out due to high miles or insufficient lubrication. Not a critical failure, but not a good sign either. Transmission must be removed and rebuilt, sooner rather than later.
21. No movement in any gear: pump failure, or total loss of fluid. Remove transmission and rebuild, or refill pan and find the leak. If out of fluid, avoid running the engine until the transmission is refilled to avoid pump damage. To check for pump failure, check fluid level with the engine off, then start the engine and recheck fluid level. If level does not go down when engine is running, the pump is broken.
22. Transmission does not shift automatically, only manually. New PCM, check wiring, check other sensors such as VSS and TPS.
23. 3rd gear starts, can manually shift through all gears. When car has been turned off for a bit, then back on it will run normally.: VSS dropoff w/ Hi-stall converter. The rpms are too high, but VSS is showing no movement. Happens after a tire burning take-off. Doesn't store a code, will not throw a CEL (I've heard that it will store a code if it happens 3 or more times). Cure: Reprogram PCM for VSS dropoff.
24. Fluid leak out of the front of trans where the converter connects; partial or full loss of movement: Front pump bushing walked out. Transmission must be removed and rebuilt. May have to replace converter also if hub is scored. Note that a leaking front seal usually means the bushing is walking out.
25. Torque converter shudder in 4th while lockup is engaged; problem goes away when the brake pedal is pressed slightly to unlock converter: Need to verify line pressure, and provided no valves in the TCC (Torque Converter Clutch) hydraulic circuit are worn, replace the torque converter.
26. Shift suddenly become very hard. When going from park to either reverse or drive it slams into gear. 1-2 and 2-3 shifts are also harsh. All gears seems to work. Problem may be intermittent: Check TPS for smooth electrical response. If the response is jumpy or erratic at all, replace TPS (Throttle position sensor).
27. All fluid pumped out through the vent tube: Plugged cooler line. Flush the transmission cooler and cooler lines. Also could be overfilled transmission.
28. Car acts like it's in OD in neutral, car is locked stationary in R, engine feels loaded in P, all four forward positions work fine: Transmission must be removed and rebuilt. Internal crossleak feeding the forward clutches all the time. Most likely a cracked input housing, or cracked forward piston means forward clutches are fused together. Car can safely be driven gently in forward gears until the repair.
29. Needle bearings in the pan, first gear and/or reverse may be noisy: Either a Torrington bearing or a planetary bearing is on its way out. Transmission will eventually die a loud, catastrophic death. Cheaper to rebuild now (saves further damage to hard parts), but requires removal and rebuild. It is drivable until it breaks.
30. 1-2 or 2-3 shift is slow/soft above part throttle: Transmission is on its way out. Transmission must be removed and rebuilt.
Common "weak spots" in 4L60E Transmission problems:
Below is a list of the weak points in a 4L60E transmission. These need an upgrade when putting more than ~300 horsepower through a 4L60E:
•Overrun clutch hub
•Input sprag (for extended high speed/load use in 4th)
•Sun gear shell
And here it is, the short list of common problems with the 4L60E Transmission and repair:
1) Slow, slipping or no reverse
2) Shifting is delayed
3) Loud bang or grinding noises
4) Loss of all gears
Hope this at least provides for some good reading.