woodsracer

I have a 2017 Lariat FX4 with 1200 miles. I am comparing my parts with stock suspension parts on the raptor and also lower capacity models because I only tow a 1800 lb popup camper with a dirt bike in the bed at heaviest. The goal is to set the truck up for handling commuting which I'll be doing on the weekdays and pulling low weight on the weekends on fairly rough roads. I hit both pavement and dirt roads but when I really want to hit it I get on my dirt bike, so nothing crazy in the truck. Rough mountain roads are common. First I'll deal with springs to suit my needs, then shocks later.

- I have FL3Z-5560-C leaf spring stocks I believe (they are marked "P FL34 5560 CH" on parts) because there are only part numbers FL3Z-5560-A or B or C or D listed as options on Ford part site. Part FL3Z-5560-A is on the lower capacity models I heard and so I assume A is lightest rate and D is stiffest. Confirmation? I bought the A's and will install next week - fun fact: without axle spacers to level rear. Not interested in lifting.

- When I look up the Raptor parts the same exact options are given for leaf springs as for 4wd FX4. Do they use the A's then or something else? Anyone have confirmation on parts on their raptor?

- For front springs the options are FL3Z-5310-A or B or C or D or E or F. These are all listed "w/o raptor" and the only option that says "w/ raptor" has part number HL3Z-5310-A. The A makes me think I'm on the right track thinking the raptor uses the leaf springs marked A, but it seems unlikely these springs will fit the non raptors because the control arms are different and there is only one shock mount listed and it's for the raptor only. My coil springs are marked FL343AH which is not an option so not sure which ones they are.

Does anyone know spring rate values for each part number front or rear? Does raptor use FL3Z-5560-A leaf springs and do the letters at the end increase with increasing rate? Can anyone give their impression of replacing FX4 shocks with Bilstein 4600 or the adjustable Ranchos?

Also, my shock numbers do not match anything I see listed on parts site. My rears say GL34 18080, fronts GL34 18045. And looked up VIN on this forum and states "Spring Capacity - Front 3500 lbs, Spring Capacity - Rear 3300"

woodsracer

127 views and nothing?

chimmike

I'd start with shocks first and you may find you don't need to mess with the springs.

Indy2015

Correct me if I'm wrong, but I've always thought the last letter designation was for engineering revisions to the same part. So the spring FL3Z-5310-A is the first iteration, with the -B, -C, etc., being subsequent revisions to the same spring. No major changes like load capacity or geometry change, but minor changes in steel tensile strength or exterior paint type or thickness.

woodsracer

I was told the A's are what are on the lower capacity models (2wd, std cab, etc) and it was assumed that the letter scaled with capacity. I happen to have the C springs.

woodsracer

Just thought I would share my research findings on this, comparing high and low rated '17 F150s. Front spring part numbers are FL3Z-5310-A/B/C/D/E/F/G/H/J/K/L/M, where the letter depends on capacity. Rear leafs are FL3Z-5560-A/B/C/D, where again letter depends on capacity.

Here are the parts on these models, the format is (front GAWR/rear GAWR, max GVWR), Front letter=, Rear letter=

SuperCrew--4wd 145WB 3.5 EB (3525/3800, 7000) F=K, R=C
SuperCrew--2wd 145WB std V6 (3225/3300, 6150) F=D, R=A
Super Cab---2wd 145WB std V6 (3225/3300, 6100) F=D, R=A
Reglr Cab----4wd 122WB std V6 (3000/3300, 6050) F=C, R=A
Reglr Cab----2wd 122WB std V6 (3000/3300, 6010) F=B, R=A

From this I think it is safe to conclude that the low letters correspond to softest spring rate and that rate increases as letters go up. My truck has the specs listed at the top with 7000 lb GVWR, and the goal is to soften both ends because I tow a light load. I already have the "A" leafs in my garage waiting to be installed, now I just need to decide what front spring would match best.

I'm thinking of stepping down from K to D in the front to match the A in the rear. Any lower and they may be too soft. What do you guys think?

Jefftopgun

Bumping this up for results...

squidpocalypse

Get a coilover kit up front with shocks and deavers out back and be done with it...(L/T kit).

IIRC, on the last gen, the raptor leaf spring packs were just standard F150 springs with the overload spring removed hence the reduced payload. The rates weren’t any different (except maybe compared to the max tow trucks).