I have an intermittent shift prob on my ’95 6.5L w/4L80. Usually when putting the trans into Drive, the truck will feel like it is slipping in 1st gear. Slide the shifter down to 2, and it engages in 1st gear fine with a solid shift to 2nd. Shift to D from there and the remaining shifts usually occur fine. Sometimes the shift from 2 to 3 requires the same manual shift, but more often than not it works fine on its own.

Occasionally it will take off in D fine. Seems like it might be associated with the trans being warm and placed in P with engine still running, but I am not absolutely sure.

Ran the diagnostics and all that popped was a code 41, indicating brake problems (correct as the ABS light is on). SES light is not otherwise on. One thing worth mentioning is that the light just automatically started flashing an un-ending 41 without the 12 beginning and ending indicated in the FAQ.

I was originally thinking solenoids due to the intermittent nature of the problem, but now I am not so sure. I recall reading about wire harness issues before… could that be a problem here as well? Since I get a solid engagement and shift from 1st to 2nd when placed in 2, I want to rule out worn bands, but not being a trans expert, I cant be sure.

Any suggestions? Thanks!

Code 41 is a brake switch circuit fault, and very well could cause shifting problems if the ECM thinks your applying the brakes when your not.

http://www.kennedydiesel.com/readcodes.html

Interesting... any idea as to what type of brake fault would lead to the kind of shift problems I am experiencing? I assume the ECM gets its readings from the brake pedal switch, but if ABS plays a role, it could get ugly.

Apparently this has nothing to do with the brakes... any suggestions for troubleshooting? Should I try a flush and change filter? If yes with the flush, any suggestions as to type? Could a flush be a bad thing?

After re-reading your post I remember my uncle having the same exact problem on his 4L60E in his 98 Z71 1500 gasser. It ended up being a bad shift solonoid, we changed all of them so I can't tell you which one it was. If you check E-bay there is a guy who sells the complete solonoid kit's for under $100, don't remember what his I.D. was though.

Thanks. Apparently the symptoms I have been having are not that common... or at least not consistent with how most people describe their trans acting prior to a solenoid change. Good to hear that mine isn't the only one doing this. I'm definitely going to order the full kit on eBay.