Model of belt used in john deere d140 models: gx21833
as product features;
Specification Belt Section HA Effective Length 141.709 IN Width 0.559 IN Thickness 0.449 IN Angle 38 Material Spec ARAMID
This kit also fits the following John Deere 100 Series Models: 145, LA145, LA155, LA165, X140, X165, D140, D150, D160
I also add a video to find out how to change it. you do not have any problems when you buy original parts and perform operations like video.
the price of this product ranges from $ 30- $ 40. you can easily find it on Amazon.
if it is not suitable for you, you can look at other belt models.