DW987 Transmission or Gearbox?

[Waferboy]

I'm having trouble determining which part is bad in my DW987. The clutch does seem to grab fine ~if~ the chuck turns. The motor turns but the chuck doesn't. It will seem to work fairly well if I point the drill down or tap the chuck face on the countertop. But after a bit it will stop spinning again.

I'm leaning towards the transmission. Any help/thoughts would be great!

Thanks!

[Tinkerdave]

Hi Waferboy, The part you need is Transmission Part Number: 397892-05SV.But check you date code as this might be warranty as Dewalt had a lot of problems with this transmission unit.Hope that helps.
Tinker