Nissan Repair: 89 maxima-Transmission/solenoid/speedo/module, bosse speakers, nissan maxima

Question
My 89' Nissan Maxima J30 Automatic 3.0l V6 has a history of Transmission problems and is starting to cost alot.  About three Years before I bought the Car the Trany was replaced.  Then four Weeks after I bought it the Tourque Converter was rebuild.  Of course, a Year later and  just after Warranty ran out, the Transmission started to slip and maybe shortly before the Speedometre misread.  The slipping got so bad ,I brought the Car to a Transmission Shop and the Solenoids were replaced, because the Transmission Fluids weren't getting pressurized enough to shift Gears.  The Transmission stoped slippig and the Car was fine with the exeption of the Speedometre misreading.  But once the Car is warm the Speedo reads fine.  The Transmission slips when stopping and getting going right awawy.  Also Feels like Transmission can't shift down.  This does not go away once the Car is warm.  Self installed Stereo System isn't working right.  Sub cuts out and or Bosse Speakers, when turning it up.  Found a cheep working Transmission control computer module, can I install it myself to try to repair the above listed Problems?  Please can you help me.  THANK YOU FOR YOUR TIME! Manuel  

Answer
Manuel,

Yes, you can replace the computer module with noot too much work.  but, from the sounds of it you also have a pump that is going out and loosing pressure.  If it were me I would replace the pump while I was at it.  You could rob it from the other transmission.