My mom has a 2005 Buick Rainier CXL. Starting yesterday the back wheels lock up when you try to make a turn. It moves fine when you’re going straight
The Eaton rear diff on these vehicles can start making noise if the rear diff fluid isn’t maintained.
Have the rear diff fluid serviced.
Do you know if the vehicle has a locking/limited slip rear differential (look at the option list in the glove box for RPO code G80)? If it does, it would be GM’s governor lock differential, and it could be locking up when it’s not supposed to. It may need differential service to free up or repair the governor assembly.
Has it been sitting un-driven for some lenth of time recently? My truck has exhibited a similar symptom, not the rear wheels locking up so much as just dragging a little when making turns at slow speed. Differential clutch issue, as mentioned above. Only happened after the truck wasn’t driven for several months. Returning to a daily driving schedule for a couple weeks fixed the problem. As long as I drive it once or week or so, it doesn’t happen.
Advice to have the rear differential serviced is probably where to start.
If you cannot find any info on what rear end was installed at the factory, you can take the Vin # to any GM dealer and they can print off everything that went into that car at the factory. Rear end type, tranny type, engine, security system, right down to the color of the seats.
Is the drive selector set to 4 low, or hi?