Thomas:
I understand you want to know what will be the effects of running a gear pump 40% greater than its rated rpm. Your question is vague in that you don't tell us WHAT fluid you are pumping and under what CONDITIONS. I have operated gear pumps - such as the Northern model that Breizh has given you information on - well over 25% capacity. But that was on hydraulic applications - pumping oil at 100 oF and 2,500 psig discharge. The fluid was a self-lubricating one and Northern had no problems in approving the operation.
You also haven't told us what TYPE of gear pump you are dealing with. There are several types of these positive displacement pumps and it makes a marked difference. Whatever our Forum comments may be, rest assured that we would always warn you not to exceed the manufacturer's recommended loadings on the pump without consulting with the manufacturer (not the sales representative or distributor).