Good morning Bruce and thank you for your assistance.
Your above Parts Diagram is very helpful and indicates the transaxle as being K1132-11110 which, from what I have just read, has now been replaced by K1132-11120, being a HST3500. Referencing this, it appears to be from the Hydro-Gear GT-3500 series, which has about 8 different models, so it looks like I will still need my nephew to get a copy of the transaxle identification label to verify the actual part reference numbers to confirm his actual installed.
As a side note, Transaxle parts K1132-11110, K1132-11120 and K1082-11110 are not listed in my 2009 HydroGear Cross Reference information, but I do have K1132-11111 and K1082-11111, along with the list of GT-3500 series models.
I am using the 2009 Hydro-Gear Cross Reference Tables found here, from Outdoor Distributors: -
http://www.outdoordistributors.com/...ross_reference_-And-_Service_Pricing.pdfA couple of sites I have found helpful for exploded transaxle diagrams are: -
K&T Parts House
http://www.mymowerparts.com/pdf/Hyd...-Parts-Lists-and-Service-Repair-Manuals/M & D Mower and Appliance
https://www.m-and-d.com/Hydro-Gear_parts.htmlAlso from M & D Mower and Appliance, I have their Model Cross-Reference sheets
https://www.m-and-d.com/pdfs/hydrogear/HYD_Model_Xref.pdfJust confirms the fact that one needs to have full details of the equipment being repaired before any serious effort can be made to find parts.