  By applying the Error PDF Updating Method, we analyze the impact of the
absolute and normalized single differential cross-sections for top-quark pair
production data from the ATLAS and CMS experiments at the Large Hadron
Collider, at a centre-of-mass energy of $\sqrt{s}= 8$ TeV, on the CT14HERA2
PDFs. We find that the top quark pair single differential distributions provide
minor constraints on the CT14HERA2 gluon PDF when the nominal CT14HERA2
inclusive jet production data are included in the fit. Larger constraints on
the gluon distribution are present when the jet data are removed (CT14HERA2mJ)
and/or when increased weights are given to the top data in the CT14HERA2 fits.
The weighted $t\bar t$ data provide significant constraints on the CT14HERA2mJ
gluon PDF, that are comparable to those obtained from inclusive jet production
data. Furthermore, we examine the top quark mass sensitivity of the top-quark
pair single differential distributions.
