Transmission Issues... need advice

This morning, on the way to work, I had an "interesting" issue with my 2005 V8 Limited 4runner... From a stop, it would barely accelerate... up to around 20 mph. Depressing the accelerator did nothing. Didn't hear squealing, but radio was on. Once I got to a slightly downhill section of the road, the speed would pick up, & eventually would shift (HARD) into the next gear. Did this several times. Finally turned around & headed back home to switch cars. I've had instances before, where, when sitting on an incline (in gear), the truck would quickly start to roll backwards. I also had an issue a few months ago where I got a code for shift solenoid, (it was 12 degrees that morning) but this seems more like torque converter? Has 171,000 on the odometer. Will go through the records I have & see if it has been serviced at all. I have no check engine light. Is a drain & fill the best/first course of action? I understand that multiple drain & fills are recommended. Also, what is everyone's experiences with the cheap, aftermarket shift solenoids? Yea, they're 1/10th the cost of Toyota parts, but do you get what you pay for? Looking for best advice/approach to this situation. Thanks.

 

No dont don’t do multiple drain and fills. When you drain all of it that friction material is gone. Your Tran’s needs that. You will make it worse. I’d first check the level first but I’d also think it may be that shift solenoid you mentioned. Please don’t do a flush of the entire system. It can make things a whole lot worse

 

Don't buy aftermarket solenoids! Yes, they are 1/10th the price, but you'll need 10x more of them as most times they either don't work or they work then die and you're back at square one. I'd make sure fluid is topped off as suggested and if that's not it, figure $1k-$3500 for either a new transmission installed or a used one installed...