92 Toyota dolphin runs good but does not accelerate at times it’ll do 60 to 70mph but other times I can’t get it past 40 to 45...
Only has 53k miles on it engine is tip top, wondering if I can upgrade the transmission for long road trips.
My mechanic said something about a Allison transmission I don’t anything about it..
please advise...

 

I advise you to give waaaaaay more info, thanks.

 

Welcome!

Yes, we need much more information like:

• What engine is in the Dolphin?
• What transmission is in the Dolphin now? Is it automatic or manual?
• Do you only have the 40 to 45 mph maximum speed going up hills? Is there any pattern as to when this problem occurs?
• Is the transmission in the right gear for driving conditions?
• Is there a problem shifting when this problem occurs?
• Is the "Check Engine" light on?