2000 S80 Automatic gearbox selection problem

jh berning · Post by **jh berning** » 13 Mar 2015, 00:47

Hi, I have a Volvo S80 2000 model. the problem that I have is when I drive at about 80km/h the gearbox engages 4th gear and immediately kicks back to 3rd gear. At this speed it keeps on shifting between 3rd and 4th gear. Above 100km/h it stays in 4th gear and seems to have no problem staying there. Driving it in manual there is no problem. What could be the problem?

jbkeene · Post by **jbkeene** » 13 Mar 2015, 10:44

maybe dirt in a solenoid valve?

try draining the fluid and filter change
it will change out about 1/2 of the fluid
also maybe change rear fluid as well

they sell kits to do this at FCP or IPD

make sure you use the proper fluid...DEX VI for a GM tranny
when I did this, I replaced the 1/2 fluid with Castrol synthetic DEX VI and didn't have a problem
the synthetic is a good detergent to clean things out

I now am at full synthetic...having sucked a liter-at-a-time out, over a year's period, replacing it with the Castrol

smooth as butter

also, read up on the horror stories on this forum of people switching to synthetic before you do this