Cummins/Onan NTA855 — Angular Alignment Procedure (750 kW Gensets and Larger)
Adjustments · Generator to engine flywheel housing
For the Cummins/Onan NTA855, from the Cummins/Onan service manual.
Applies to: Cummins/Onan DFAB, Cummins/Onan DFAC, Cummins/Onan DFBF, Cummins/Onan DFCC, Cummins/Onan DFCE, Cummins/Onan NTA855, Cummins/Onan LTA10 engine, Cummins/Onan NT855 engine, Cummins/Onan NTA855 engine
Before you start
- Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death. Disconnect the negative (-) battery cable(s) before beginning.
- Do not bar engine over by prying on fan blade. This may damage the blade and result in premature, sudden blade failure.
Procedure
- Fasten dial indicator to generator shaft or cooling fan with sensing point on capscrew head or drive disc flat at bolt circle diameter.
- Bar engine over clockwise as viewed from flywheel; do not allow it to roll back on compression.
- T.I.R. is sum of maximum positive and negative dial readings over one revolution.
- Compare distances from step measurements to determine shim adjustment.
- Remove or add equal shims from under generator mounting feet as calculated.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- T.I.R. should not be more than .001 inch for each inch of radius
- Maximum T.I.R. example at 10.7 inches = .011 inch
Full service-parts list: Cummins/Onan DFBF →, Cummins/Onan DFCC →, Cummins/Onan DFCE →
Source: Cummins/Onan 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.