Performance Upgrade Path for a 1999 S80 T6
Short answer: there isn’t one. Long answer: there is, if you’re willing to spend lots of money to get there, and find a way around an inherently weak transmission. S80 performance isn’t easy.
To be blunt, it’s best to get another Volvo to add performance to. The S80 has few aftermarket performance products made for it.
Volvo used a version of the GM 4T65-E trans in the S80 T6, the 4T65-E is the same transmission in the late ’90s early ’00s Pontiac Grand Prix, Chevy Lumina, Monte carol, Buick Aurora, etc. I had a ’94 3.1L Grand Prix, with the older 4T60-E and it was as reliable as a hammer, I put dang near 300K miles on it’s transmission, but went through 2 engines. I don’t know what Volvo did to the trans, or if it simply can’t handle the T6’s power, the failure rate has puzzled me ever since I started researching my parent’s S80.”
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