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Hello,
Im working on a 1999 gmc sierra 5.3 4×4 with the 4l60e transmission. The customer had the transmission replaced a little under a year ago. It started slipping and not wanting to shift and since it was still under warrenty, he took it to me. I pulled codes and saw a code for shift solenoid b performance. When I test drove the car, it was late shifting into 3rd gear and when it did, it slipped badly. 1st and 2nd did not slip at all. I dropped the pan and found the remanants of the 3-4 clutch so I dropped the trans and sent it off to get another rebuild from the shop that did the first rebuild. The shop said the 3-4 clutchpack was destroyed and the sunshell was cracked as is common with these transmissions. The claim to have replaced shift solenoid b as well and the code has not returned. After putting the transmission back in, the code for the shift solenoid did not come back and the shifting issue was fixed, As soon as the trans shifted into 3rd though, it started slipping, just like before. I verified line pressure in all ranges and it was well within spec. Shift solenoids in my experiences dont cause slipping and I did not have any codes. In the 4l60e, both shift solenoids (a and b) are on in first, solenoid b is on in 2nd, neither are on in 3rd, and a is on in 4th. Because of this, i disconnected the case connector and took it for another test drive. Miraculously the transmission did not slip at all. The trans felt like it was stuck in 3rd, as it should be with that connector unplugged. What would cause 3rd to slip only with the connector plugged in? I was confused so i checked for a short to ground on the control side of shift solenoid b (thinking that solenoid being on all the time may have something to do with my issue), there was no short to ground. I also watched my scan tool to verify that my VSS signal was not dropping out, it was not. Im running out of ideas, any diagnostitions out there have any ideas?
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I will check to see if that ground stays after it shifts to third. I already checked for a short to ground on that wire and did not have one but if a transistor driver in the PCM wasnt turning off that would make sense. Thanks, will report back.
I fixed this issue. I pulled the pan and removed shift solenoids a and b. I tested them by applying 12 v and both clicked and drew equal current and did not allow me to blow air through them when energized. When not energized however, shift solenoid b was much more restrictive when I blew through it. I replaced this solenoid and the transmission stopped slipping.
[quote=”americantractors123″ post=131853]I fixed this issue. I pulled the pan and removed shift solenoids a and b. I tested them by applying 12 v and both clicked and drew equal current and did not allow me to blow air through them when energized. When not energized however, shift solenoid b was much more restrictive when I blew through it. I replaced this solenoid and the transmission stopped slipping.[/quote]
Good deal on finding the solenoid problem. 🙂
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