2000 Regal, very clean so Id like to keep the car. Has no 4th gear. Its shifting into 4th but not engaging.
Its probably the 4th gear clutch hub where the spline has worn down.
Has anyone here replaced it or had a shop do it?

Moved to "Buick" forum. As stated in the "General GM Chat" forum'* description: "all Model specific mechanical problems should be posted in the proper forum."

This will help others more-easily find useful threads in the future.

Maybe.

Was it a sudden loss?

How many miles are on it?

sudden, 207,000

It could be the clutch hub, but I haven't heard of any just suddenly going out without other warnings or contributing factors, especially post-1998 model year. I'd suspect a shift solenoid, electrical issue, or shift-cable adjustment first.

If it is the clutch hub, you will be just as well off doing a full overhaul while you're that far in. I'd suspect any decent shop won't take a twenty-year-old transaxle that far apart without doing an overhaul anyways.

I'd be curious to know what Transmission codes may be stored.
Anyone with a commercial scanner should be able to pull the codes including any trans shop.