Not sure exactly how the current 1740# HF trailers front & rear chassis sections go together. When I bought my 1740# (variously listed as 1720, 1740, 1800, etc.) in 2006 the chassis assembled in 2 sections & the front & rear sections simply bolted together with 2 or 4 bolts thru the cross pieces, & the spring hanger (a piece of 'u' channel welded to steel angle) bolted to each half, reinforcing the chassis. I just removed the 2 cross pieces that bolt together, slipped 'em inside the 'c' channel side rails. drilled a couple of extra holes & bolted it all together. The 2cross pieces make excellent reinforcing pieces. I then moved the spring hanger mount back approx 4", drilled new holes after '
squaring' the axle to the coupler, & bolted it up. When I was ready to install my 5x9' floor on the 4x8' chassis I substituted a 'fitted' wood 2x4 for the 2 missing crosspieces. Made my maiden voyage in the TD in Sept 2006 & have towed it near 20K miles since with absolutely NO problems with chassis integrity. When I was rear ended Labor Day weekend 2010 my TD survived with little damage to the body & only damage to the chassis was to the rear cross member & 1 stabilizing jack. I credit part of that to the extra rigidity of the chassis side rails with the 'cross piece' inserts.
This is a diagram from HF showing how the 2 chassis sections fit together
![Image](https://www.tnttt.com/gallery/image.php?album_id=1871&image_id=7597)
Drilling extra holes for the 'cross pieces' nestled (clamped) inside the side rails of the 2 chassis halves, & new holes for he axle spring mount to be moved towards the rear.
![Image](https://www.tnttt.com/gallery/image.php?album_id=1871&image_id=6373)
Axle spring mount moved back to the rear chassis half (mostly). You can see the extra bolts & if you look carefully you can faintly see the 'butt' joint of the chassis half side rail just in front of the fender nearest the camera
![Image](https://www.tnttt.com/gallery/image.php?album_id=1871&image_id=7257)
The wood cross member that replaced the 2 metal pieces used in reinforcing the side rails. In the first 2 pix you can easily see the cross members bolted inside the side rails...
![Image](https://www.tnttt.com/gallery/image.php?album_id=1871&image_id=9688)
![Image](https://www.tnttt.com/gallery/image.php?album_id=1871&image_id=9686)
![Image](https://www.tnttt.com/gallery/image.php?album_id=1871&image_id=9866)