Decoder type in my Bachmann EMD GP 35

[yguy]

I want to consist this engine with  an Intermoutain Emd F9B # 4959S loco with a QSI sound .
Both units have different speed ratios-- would welcome suggestions on how to consist both of them together so that I do not overtax one engine over the other

HO RTR GP35 w/DCC, CPR/Multimark #5003
Specs
DCC:Yes but no sound on board
GP35 DCC Equipped CP Multi Mark #5003

[lmackattack]

if the Bachmann Gp35 just has basic motor control you will likely have more luck getting the QSI equipped engine to match it by adjusting its speed tables. most times its the mid point settings need to be adjusted to speed match locos with diffrent gearing