![]() In addition, the chart can be helpful if you suspect a component problem. It is good to confirm the integrity of a sprag clutch before performing a rebuild, because you may not be able to tell when the transmission is disassembled and you are holding it in your hand. If you do not have engine braking, it points to the low/rev clutch being bad and preventing reverse. This would indicate that the reverse input clutch is the cause. ![]() If engine braking is working, that indicates that the low/rev clutch is correctly holding the sprag clutch from overrunning. An easy way to test this is to accelerate to about 20mph and pull it into manual low to see if you have engine braking when you let off the gas. What if I have all forward gears but no reverse? A look at the application chart shows that the reverse input clutch and the low/rev clutch engage to engage reverse gear. ![]() Sometimes the sun gear will break away from the sun shell on the 4L60E units and you will lose second, fourth, and reverse gears which then require the replacement of the sun shell. That would indicate that the solenoids are working ok and point to a friction element, and as the chart shows, the common element applied in second and fourth gears is the 2-4 band. Remember that in first gear both shift solenoids are on and in third gear, both are off. They might think that it is then in second gear, but they are actually in third gear and may not notice that there is no upshift into fourth gear. Many times I have had customers complain that their transmission stays in first gear for a long time before it finally shifts, and some will report that they have to let off the gas pedal in order to get it to shift. If I am missing second and fourth gears but all other gears are ok, the cause points to the 2-4 band not applying. If there is now movement, the forward sprag is bad because the overrunning clutch holds the sprag, but if it still does not move then it is the forward clutch causing the concern. If I have no movement from a stop I can test to see whether the forward clutch is bad, or if the forward sprag clutch is not holding, by shifting into manual low. If the 3-4 clutch does not hold, the transmission remains in second gear because the forward clutch and the 2-4 band are holding, thus indicating that the 3-4 clutch is not. Referring to the chart, I see that the 2-4 band applies at this point. If I have a second gear ratio when fourth gear is commanded, it will reveal the cause: the 3-4 clutch is not holding. Next, I shift to manual second while increasing the vehicle speed until about 40mph, then shift to overdrive and let off the gas. Testing further, I know that on the shift from second to third gear that the 2-4 band turns off and the 3-4 clutch applies. In third gear both solenoids are off, so when I feel the neutral condition, it is a good sign that SSB is turning off so I can then conclude that both solenoids are working properly. When second gear is commanded, SSA turns off. If the vehicle is shifting to first and second gear and feels like it neutrals when third is commanded, a review of the solenoids shows that both are on for first gear, so I know that both are turning on. I will use the 4L60E transmission for the following scenarios (refer to FIG. When I have a shifting issue, a review of what solenoids and friction elements are applied in each gear can let me see what areas of the transmission the problem may be caused by, so I can then differentiate whether there is an electrical or mechanical issue causing the symptoms. One of the best and easiest diagnostic tools that I use almost daily for diagnosing transmission problems is pass book or application chart information. Barry and his wife Janet have been married 42 years and are proud parents of 6 children and 26 grandchildren. with L1 advanced level diagnostics, the highest level of certification available. He has done everything from managing, owning, and operating his own general repair facility to working in the transmission industry. Barry has over 45 years of automotive experience.
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