Where can i find a free service manual for LG WM3431HW?

Call the manufacturer.

A) There's no toe-kick
b) The manual is 44 pages long. I've never seen a full-sized repair manual included with a product.

Unfortunately you won't find one.

LG only supply their servicing manuals to their repair centres and strictly enforce their copyright, so the manuals are not available to the public and when they do occasionally appear the material has been stolen.

Usually I'd recommend a generic repair manual such as the one by Haynes, but LG's direct drive system and a number of other unique technical features mean that the Haynes book isn't as useful as it could be. The WM3431HW is a large capacity and technically advanced washer dryer so it's certainly not as straightforward to service as a traditional front loading washer or dryer. Many LG spare parts can also be difficult to source outside of their own approved servicing organisation.

I respectfully suggest that you either get LG to fix your machine or post a question on this site describing the problem to see if we can assist you.