4L80e Failure
09-16-2013, 09:13 AM
#1
4L80e Failure This past weekend I had my car on a local shops dyno for a few pulls to so we could see what the new turbo was doing, and where power was dropping off. On one of the pulls, the dyno operator threw the selector into reverse after letting off the gas. The car was doing in excess of 140 mph when this happened. It killed the motor and came to a stop as normal. The guys standing outside of the car didn't hear any weird noises or anything, nor did I sitting in the passenger seat while running the laptop. He fired the car back up and put it in gear. It drove forward just fine.
We get the car off the dyno and when trying to put it in revers it would not move anywhere. Shut the car off, put in neutral and tried to push it backwards and still would not move. It rolled forward just fine however. After a few minutes of checking out everything underneath (driveshaft, u-joints, converter bolts, etc.) we put the car back in neutral and it rolled freely. So we started it again, put it in reverse, and it rolled back like it should. We were originally thinking that maybe the trans was ok and something let go in the rear end. Well I tried to drive it a short distance and it shifted fine all the way to 3rd gear. When I came up to a stop though, and the trans downshifted, it felt as if something really pulling on me to stop. Then it started to take some decent throttle to get it to go anywhere. Got out and checked over things again and found nothing. Hopped back in the car to move it to a better location for to get it on a trailer and it seemed to drive fine going forward again. Reverse on the other hand, was completely gone. I drove it on the trailer just fine though.
So my questions are, what likely happened inside the trans when it was thrown into reverse at that speed? Could it have done damage to more than just the reverse band? I plan on dropping the pan tonight to see what kind of debris is laying in there. If the trans needs pulled and repaired, do I absolutely need to have the converter gone through?
Thanks for any help.
We get the car off the dyno and when trying to put it in revers it would not move anywhere. Shut the car off, put in neutral and tried to push it backwards and still would not move. It rolled forward just fine however. After a few minutes of checking out everything underneath (driveshaft, u-joints, converter bolts, etc.) we put the car back in neutral and it rolled freely. So we started it again, put it in reverse, and it rolled back like it should. We were originally thinking that maybe the trans was ok and something let go in the rear end. Well I tried to drive it a short distance and it shifted fine all the way to 3rd gear. When I came up to a stop though, and the trans downshifted, it felt as if something really pulling on me to stop. Then it started to take some decent throttle to get it to go anywhere. Got out and checked over things again and found nothing. Hopped back in the car to move it to a better location for to get it on a trailer and it seemed to drive fine going forward again. Reverse on the other hand, was completely gone. I drove it on the trailer just fine though.
So my questions are, what likely happened inside the trans when it was thrown into reverse at that speed? Could it have done damage to more than just the reverse band? I plan on dropping the pan tonight to see what kind of debris is laying in there. If the trans needs pulled and repaired, do I absolutely need to have the converter gone through?
Thanks for any help.
09-16-2013, 09:39 AM
#2
The first thing I would ask is "Why was the car ever shifted at all?" It sounds as if they tried to shift to neutral after the pull. That's asking for an explosion and the dyno operator should know better. Let the car come down on it's own.
I would be suspect of every splined joint, sprag, and shaft in it. Band will be burnt.
I would be suspect of every splined joint, sprag, and shaft in it. Band will be burnt.
09-16-2013, 09:52 AM
#3
My thoughts exactly Jake. It would be no different then doing a pull on the interstate and slowing down. I realize that it was an accident, mistake, whatever you want to call it though. I just hope we can come to an agreement that he should at least help pay for the replacement or the repair of the trans.
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09-17-2013, 07:31 AM
#8
He is helping to take care of it. He is a good friend of mine and made a mistake. Not the end of the world by any means. At least now I can beat on the car again while I save up to build a better than stock trans.
Is there anything I can do to clean out the converter? I want the car back on the road as quickly as possible and wont have time to send it back to Chris.
Is there anything I can do to clean out the converter? I want the car back on the road as quickly as possible and wont have time to send it back to Chris.
