need some trans help..tf3 won't upshift

Which servo, Front or rear? If it's the rear servo and it's sticking that will cause it to engage into reverse slow but wont' affect it upshifting unless it doesn't release properly. If the front servo is hanging up it will cause no upshift. Neither servo will cause it to be slow engaging into first. The rear servo is active in low but it's not needed for low gear. It's just there so the sprague doesn't have to take all the grunt. The front servo gives you 2nd gear when it's applied.

By your description it sounds more like a low hydraulic pressure problem.

IMO: any time you install a servo you need to air pressure test it to see if it works properly.