Operation Market Garden Logistics

Chester Wilmot in his 1952 book The Struggle for Europe stated that just before Op Market Garden 1400 British 3-ton trucks were off the road due to faulty pistons which led to supply problems for OMG. This comment is repeated in Ryan -A Bridge Too Far and Horne - Montgomery The Lonely Leader. Someone I know wrote to Horne questioning this and got a reply stating that he wasn't sure where this piece of information came from! I personally wouldn't be happy putting a fact in a book without being 100% happy with it.
Does anyone on the forum know if this figure of 1,400 is true or is it another one of these mythical facts that's been serially repeated by authors who fail to carry out proper research like the 'fact' that all the Recce Squadron jeeps failed to get to Arnhem- when in fact 28 out of 32 did......

 

Which page?

Is there a reference in Wilmots book to some primary document?