Donlan, 34, was assistant to Ian Millward at Castleford until both were sacked just over a month ago.
He takes the place of Sean Long, who resigned last month and subsequently joined Wigan, and will not be the last addition to the City Reds' backroom staff as Noble looks to turn around the club's fortunes.
"It's certainly not complete," Noble said. "This team does have a bit of catching up to do on the coaching front and the more resources we can throw at that, the quicker we will improve."
Salford are currently bottom of Super League and were dumped out of the Challenge Cup by holders Warrington on Sunday.
Millionaire owner Marwan Koukash has pledged to make funds available for Noble to significantly strengthen the squad, and the club continue to be linked with Castleford's England half-back Rangi Chase.
But Noble says no signings are imminent and has called on fans of the club to be patient.
"It's difficult to recruit in-season," Noble said. "The people that we bring in need to complement and improve on the ones we've got in there.
"I suppose we could find some people that may help with numbers if I thought it was a numbers thing, but there are some people I haven't had a look at yet that probably deserve a crack before them.
"It's important that we hold our nerve. We're on a journey and all the right decisions need to be made."
- Sports & Recreation