You might try Paden's (sp) on Killingsworth about 85th or so (last building on right eastbound before I-205). There also used to be a 4x4 shop at about 71st on Division, but after Harold sold out I am not sure the new owners were able to survive. There is also a place south of Oregon City 2 miles east of 99E that works on Jeep transmissions (and rear ends, I think), but I can't remember the name nor even the road they are on.
You might also call John at 205 Auto Wrecking as they are the only Jeep wrecking yard in the area. He might know of someone.