For the most part I hate to suggest any mechanic because every shop can foul up at one time or another. But these places are much better than many dealerships IMO.
Recommended by Advanced Adapters, this shop does custom 4x4 work. Drive train experts, Georg is quite known in the Rubicon trail 4x4 community. Their main work is with restoring older FJ's but it's nice to know an owner that actually wanted to work on my SMB just because he was impressed with it. Seeing some of the restored FJ's was a treat.
2953 E Cherryland
Stockton Ca 95215
G Street auto does most of my standard work & is a place I trust.
G Street Auto Care
2996 G St Merced, CA 95340
This little hole in the wall has been known for excellent work dealing with differentials of all types.
The Rear End Shop
2372 Patterson Rd, Riverbank, CA 95367
Justin at J's performance does bullet proofing on diesels and does specialty work on Sportsmobiles. I haven't used him yet but have been to his shop and seen their operation. Located across from the Fresno airport they are well located as a spot to drop off a vehicle that might need extended time for a major repair. Fly home and fly back when it's done.
J's Performance Automotive
Auto Parts Store
Address: 2377 N Larkin Ave #102, Fresno, CA 93727
Brown's Diesel has done work on my 6.0 PSD. Seems like a good shop and treated me fair. This place is a larger shop that deals with tons of farmers and their trucks. Very busy place. Located between I-5 and 99 west of Fresno in the middle of nowhere, I'd ask if there is even a rental car agency willing to pick you up if need be.
3832 W Mt Whitney Ave, Riverdale, CA 93656
Zylstra's rebuilt my 6.0 PSD and bullet proofed the engine. They also have done a lot of work on SMB's. It's a larger shop that works on emergency vehicles in the area. There was even a fire truck there when they did my rebuild. It's always a busy place.
2230 E Main St, Visalia, CA 93292