I'm thinking of having my turbo sent away to be rebuilt. Besides having the oil seals and bushes replaced what else is usually replaced during a turbo rebuild?

 

Is it a T3 or T4 turbo? What exactly is it?


2x Journal bearings inside the centre housing
1x Thrust washer and spigot on the front of the centre housing
1x Rear piston seal
1x O-ring between centre housing and front cover backing plate
1x front seal (can be either 3 piece carbon, carbon encapsulated or dynamic).

Some shops like to grind the turbine shaft/wheel if there are any visible groves at all on the bearing lobes. I'd prefer to replace the shaft and wheel in that case. If you have the shaft ground you use undersized bearings.

Then you have optional parts like the stagger gap rear piston seal (turbonetics)
Also 360 kits are upgraded thrust washers and allows you to remove the star spring.

I'm not sure if steel thrust washers exist I have seen pictures of washers that don't appear to be made of brass or whatever they are normally made out of.

Then you have the balance that you probably should get done but you can get by without it.

For minimum drag with a slight compromise on front sealing and highest robustness choose the stager gap rear piston seal and a dynamic front seal type 360 kit.

You can use carbon front seals instead of the dynamic/piston ring front seal but you can feel the extra drag on the turbo shaft. Carbon front seals, seal better but cause drag. Most legacy garrett turbos T04S/R etc all use 360 kit dynamic fronts.