1997 GMC K3500 PICKUP, 4L80-E

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found good tps reading at computer(return sensor) reading corectly...replace computer, same problem....then found tps dropping at idle to .001 volts intermitently setting code 22 causing computer to inhibit 4th and tcc...replaced tps solved all codes, tcc problem, and harsh shifts...but computer does not command 4th until 55 mph....all other shifts on time, and data is correct (iss,vss, trans temp,manifold pressure switch, prndl etc.)

22 tps range too low

Original Customer Complaint:
no 4th =, no tcc, harsh shifts
Current Customer Complaint:
none
Work Completed This Visit:
none
Summary:
see previous repairs section Note..as soon as computer commands shift sol.A on for 4th, trans makes a good shift and stays until speed drops....but too late (makes 2-3@27mph)

I removed the extra checkball I put in, and changed the EPC, and now it shifts fine. But the initial egagements into reverse and drive are still a little firm. It had the silver EPC and I replaced it with one from a 4L60E. The Transtar catalog has the same part# for the two. Any ideas???In my original post I indicated I had done fairly through electrical testing of the TCC circuit, and felt I had mechanical issues with TCC operation, and it still might be, but I’ve since had the chance to test drive again, now I’m not so certain. While graphing TCC duty cycle and TCC slip I noticed that the slip never got more than 37 RPM. While setting still in gear, engine rpm showed 725 RPM, input sensor showed 0 RPM, and TCC slip showed 0. Shouldn’t slip be equal to engine RPM? While driving at the time of TCC apply, I noticed the duty cycle would go from 0 to 85% almost instantly, then ramp gradually up to 100%. TCC slip will go from 37 to 0 RPM. While accelerating from a stop to the engagement point, the TCC slip never exceeds 37 RPM under light or heavy throttle. The condition parameters for setting code 68 are: in 4th gear, TCC commanded on, and over 200 RPM TCC slip for more than 2 seconds. As I said, I graphed the TCC slip, it never got more than 37 RPM, but it still sets this code. The input and output sensors have been replaced and appear good on the graphs. The RPM also looks good. I would like to confirm whether the TCC is functioning properly by manually controlling the TCC ground. If I manually grounded the TCC solenoid with the selector lever in D4 and my foot on the brake, will it kill the engine? Does the hydraulic circuit allow tcc apply in D4 first gear? I wish I could eliminate one or the other as the possible cause. My scanner don’t have the capability to control the TCC and I don’t have a transx 2000. Thanks Again to anyone who can point me in the right direction here… Steve

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