1997 Chevrolet Silverado 4x4 z71 transmission problems. 5 months ago I had it serviced and A/B shift solenoids changed along with filter and fluid. Now check engine is back on with P1860 code truck also has started shifting more firmly into second and at 65mph it gives a hard jerk. Any suggestions will be welcomed because local transmission shop wants $1800.00 to rebuild that I dont have.