4L60E Grinding, Crunching Feeling In Reverse
My buddy's 1/2 ton Chevy pickup when starting off in reverse has a grinding kind of sound. When put in drive after 25 MPH it smooths out and runs flawlessly.
Forgot to mention, I've got the drive shaft out, u-joints are fine, diff spins smoothly and hanger bearing is smooth.
Seems to be in the tranny. Just never seen this before.
Just in case anyone is doing a search for the same issue, I'll post the answer to this problem.
It looks like either the rear sun gear or planets threw a spline and ground up a few hard parts.
This was a VERY common problem with the early 700-R4 transmissions and is the main, but not only, reason to avoid 700s before mid-1984. Sometimes the rear planet exploded, destroyed the case, and literally left pieces on the roadway.
With redesign of the rear planet and rear ring gear, most of those problems disappeared, but as you see, it still happens.
For those that do not know, the 4L60-E gear train is the same gear train used in the later 700s.
As Merlin states the rear planetary up until final production of this series of transmission continued to be an Achilles heel.
Even the 5 pinion planet sets were just as susceptible to failure as the early 4 pinion sets were. The harder the owner drove the vehicle, the more likely the planet set was to fail. Any type of racing, towing, or other intentional abuse would drastically shorten the planet sets life. The secret to a long living 700/4L60E is to use it in exactly the manner that GM intended-as a basic daily driver, non-work, non-racing, non-hi-performance, non-towing, vehicle. When used CORRECTLY in that manner, you are guaranteed to go at least 150K miles. If you attempt to do anything else OTHER THAN using them as daily drivers then it's a roll of the dice and snake eyes usually equated to a stripped sunshell or failed low planet set, or broken input sprag, or burnt 3rd & 4th clutch pack, or stripped turbine shaft to input drum, or.... you see where this is going.
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