Detroit Diesel — Crankshaft Grinding
Repair & overhaul
From a Detroit Diesel service manual — check it applies to your exact model before use.
Before you start
- Any crankshaft with cracks starting at an oil hole and following the journal surface at 45° to the axis must be rejected.
Procedure
- Compare the crankshaft journal measurements with the dimensions in Table 2 to determine the size to which the journals are to be reground.
- If one or more journals require grinding, grind all of the main journals or all of the connecting rod journals to the same required size.
- All journal fillets must have a .210" to .230" radius between the crank cheek and the journal.
- Cool the crankshaft while grinding, using coolant generously.
- If the thrust surfaces are worn or grooved excessively, regrind and polish them leaving a .210" to .230" radius.
- Stone the edge of all oil holes in the journal surfaces smooth to a radius of approximately 3/32".
- After grinding, inspect the crankshaft by the magnetic particle method.
- Demagnetize the crankshaft.
- Remove the plugs, clean the crankshaft and oil passages with fuel oil, dry and reinstall the plugs.
Tools required
- Fillet gage Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Conn. rod journal dia.: Standard 3.873"/3.874"; .002" US 3.871"/3.872"; .010" US 3.863"/3.864"; .020" US 3.853"/3.854"; .030" US 3.843"/3.844"
- Main bearing journal dia.: Standard 4.872"/4.873"; .002" US 4.870"/4.871"; .010" US 4.862"/4.863"; .020" US 4.852"/4.853"; .030" US 4.842"/4.843"
- Journal fillet radius .210"-.230"
Source: Detroit Diesel service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.