- let me welcome you hear to the forums with your first post. Having owned three (3) F150 Platinums (2010/2015/2018) I must say that your 2018 Platinum w/FX4 package + 157" wheelbase + 3.55 rear axle is a bit of a "unicorn" as I didn't even think you could order an FX4 with the longer bed and 3.55 axle (I have factory ordered my last two F150s = been thru all the ordering combinations)
I don't consider myself an expert in towing (especially another vehicle) as I only occasionally tow tractors in my 7x16 enclosed dual-axle trailer. I did a bunch of reading & research in this topic to educate myself and summarized what I found here in Post #7
of the What is your payload capacity
I don't think you are beyond the GCW (Gross Combination Weight) limitation of your truck and I agree that payload capacity would be what to focus on. Please note the 5000 lb rating on the factory hitch w/o using a Weight-Distributing Hitch.
I have commented previously on how the payload capacity drops off dramatically as your move up in the trim levels, with the Platinum trim cutting the payload capacity nearly in half from the max payload capacity of a base F150.
Check the payload sticker on the Driver's side door jamb to determine what your vehicle's max payload capacity is. for my 2018 Platinum w/FX4 package + 145" wheelbase + 3.31 axle is abysmal 1084 lbs = Five (5) 200 lb passengers!
View attachment 2517
Based on this (incomplete = 3.0L Diesel was not listed) table from the 2018 F150 Ordering Guide, there is no difference in max payload for 145" WB (5.5' bed) vs vs 157" (6.5' bed) for the standard frame:
View attachment 2518
The Heavy-Duty Payload package (627) option bumps max payloads things up by 20% but I am pretty sure it was impossible to order Heavy-Duty Payload package (627) option + 3.0L V6 Diesel engine option:
View attachment 2520
- 2018 F150 Ordering Guide doesn't include 3.0L engine option in charts
- 2018 F150 Ordering Guide indicates you could order HD Payload package (627) on following trim levels:
- 2019 F150 Ordering Guide indicates you could order HD Payload package (627) on following trim levels:
so I am going to assume you don't have the Heavy-Duty Payload package (627) option on your truck.
This Axle Availability chart from the 2019 F150 Ordering Guide (3.0L V6 Diesel engine option not included in 2018 Guide) shows what I thought I remembered:
View attachment 2522
- FX4 package locks you (pun intended) into 3.31 Electronic-Locking Diff (XL3)
- Heavy-Duty Payload package only available on:
- 157" wheelbase (6.5' bed)
- Only two (2) engine options:
Not sure if I answered any of your questions (probably raised new/more questions about how you have FX4 package (55A) +157" wheelbase/6.5' bed + 3.55 axle) but wanted to provide you with what I have researched previously.
Might be interesting to use your VIN to generate a Monroney window sticker to see if FX4 package (55A) is truly installed because based on above, FX4 package + 3.55 axle are mutually exclusive = previous owner could have ordered/slapped on the FX4 decals.
Good luck with your move and welcome again to the forums!