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I just happen to have some experience running the 4.88 gears with smaller tires, for the first 2 years after my gear swap I ran 32"s. It towed like a locomotive and was like a hotrod around town unloaded but the unloaded highway mileage dropped from 14+ down to 12 MPG. The towing mileage went from a stock setup 6.5/7 MPG up to 9 MPG with the 32"/4.88 setup. That combo spun the V-10 at 2600 RPMs at 70 MPH, which is far from screaming. Now with the 35"s and the 4.88s it turns 2400 revs at 70 MPH. That RPM range makes some decent torque for towing heavy. In the current configuration with the cruise set at 65 MPH it will get 14.5 MPG on mostly flat highway.
Yeah that helps a lot. I follow and appreciate all the technical detail here…it’s important to understand it all I think…and I can manage the work….but a lay-assessment of what it produced is really what the end game here is so thanks.
I don’t tow that often…however each year we push a little further to me places and and so I’m wanting to get this Ex to tow its best…even if it’s only 4x a year.
I have the sct tuner too…helps with shifting for sure.
only other thing for me as 4.30 gears from 3.73….the v10 needs help on the hills.
thanks for rhe response.
Howdy David!
I too am riding on modded B codes, mine are also modded with a set of F-350 4"-ish blocks and 2 sections of my cut up factory traction bars along with the traditional B code mod of adding the bottom two factory short leaves. My goal was to have the "heavier" springs, gain some decent lift to fit 35"s and have the EX sit level when towing. When I did the spring swap we were towing a 31' 9,500lb TH that had 1400lbs of tongue weight and with the 1400lb spring bars on my Hensley Arrow WD hitch fully cranked up it did ride level when loaded and towing. And it gained 5.5" of ride height in the rear to go along with my modded X codes up front that give 4" of lift which all make the true 35"s fit well. That TH is long gone and we now tow a 41' 12K TT with 1860lbs of tongue weight and the 1400lb bars are the largest the Hensley can run, so I can’t get all of the weight transfer from the WD that I'd like and as a result the rear axle sees about 6300lbs when towing and it squats about 2". I know my setup isn't an apples to apples comparison to what you have described for yours but it does work well and we have logged over 49K towing miles so far (leaving on a 1200 mile trip Friday!). I'm pretty happy with how it handles our load and it is a comfortable highway tow rig, but the unloaded ride is less than perfect. Our EX is a dedicated tow rig and doesn't see any daily use, only towing and traveling around unloaded at our various destinations, so the mileage mix and suspension favors the towing setup. I run the adjustable Rancho 9000 shocks and keep my rear shocks and tire pressure set for the heavy tow load, I could air down and adjust the shocks to a softer setting for our sightseeing miles but I'm too lazy.
Since you have already upgraded your gears from 3.73 to 4.30 I would advise against going to a larger tire size unless you want to regear it again to maintain the better gear advantage the 6.8 likes so much, I have 4.88s to match my 35"s for an effective 4.39 ratio. With stock-ish sized tire's any additional lift will look a little "off" (like my signature picture here with 32"s) so I wouldn't be looking for much if any lift from your planned suspension changes. I would think adding a set airbags would get you the increased spring rate to handle the TT's tongue weight and make towing a more comfortable and squat free experience that can be easily aired down to make for a more civilized daily use ride.
If I were to build my EX again starting today I would most likely go with the ProComp 4" lift springs and add airbags to handle the towing weight on the rear. I just retired 2 weeks ago and we are planning to start more extended travels next Spring with the EX and TT and I'm thinking that a new set of bags may get added along with taking the addition spacers out of my rear spring packs to have less unloaded rake and better rear spring capacity to get to level when loaded.
There is a lot to consider when diving into this pool, take your time and try to evaluate the options thoroughly. Good luck and keep us posted.[/QUOTE]
Originally Posted by WE3ZS
I just happen to have some experience running the 4.88 gears with smaller tires, for the first 2 years after my gear swap I ran 32"s. It towed like a locomotive and was like a hotrod around town unloaded but the unloaded highway mileage dropped from 14+ down to 12 MPG. The towing mileage went from a stock setup 6.5/7 MPG up to 9 MPG with the 32"/4.88 setup. That combo spun the V-10 at 2600 RPMs at 70 MPH, which is far from screaming. Now with the 35"s and the 4.88s it turns 2400 revs at 70 MPH. That RPM range makes some decent torque for towing heavy. In the current configuration with the cruise set at 65 MPH it will get 14.5 MPG on mostly flat highway.
No I don't think 2600 is outrageous. I will probably be going to about a 34" tire....I found a nifty calculator that puts the effective ratio at around 4.43 using 4.88's and 34". That's a decent improvement for sure.
This truck I am optimizing for towing. It does get some very local use...but it's with kids and quite frankly they love getting thrown around back there .
I am sort of stuck between rear Modified B,C,F code springs....and the pro comps (or other retail).
I have done a ton of reading here and elsewhere about Spring rate compared to overall spring capacity.
I think it seems...that for straight driving....around town....the pro comps LOWER spring rate would produce a more comfortable ride and handling package. BUT ARE THEY OPTIMAL FOR HEAVY TOWING??....and I think the answer must be no. The lower rate AND overall lower capacity (even though pro comp doesn't rate the total capacity...the # of leaves I think tells the story)....would at least in my mind suggest that they'd be just as OR MORE squatty with a 10,000lb TT attached than stocks. Hence the modified B,C,F concept.
Do you agree here? really trying to figure this part out and there's so much on all sides of this issue.
Wish someone would really design a 2 stage proper spring for the EX that had a lower rate but higher overall capacity.
Last ?…..hs anyone found a need to replace those nylon spacers that are between the individual leafs? Or are they in good solid shape and not really deteriorated.
truck has about 120….could imagine little nylon spacers disintegrating when I get them apart…or they could be fine.
Last ?…..hs anyone found a need to replace those nylon spacers that are between the individual leafs? Or are they in good solid shape and not really deteriorated.
truck has about 120….could imagine little nylon spacers disintegrating when I get them apart…or they could be fine.
anyone suggest getting these….or No?
if so what’s the part?
thanks all…will post pics!
I didn’t need to either time I did this mod. Even the donor leafs from a 99 F350 from Mass (salty, lol)with 150k miles still had good delrin isolators.
but they’re cheap. I cherry picked the best from all packs to rebuild.
Typical modified B spring swap in rear, stock excursion block PLUS I added back in the excursion slapper spring with the bumper on the bottom of the stack. I did this not for function but because I knew I wanted a little more rake.
Final measurements
Front both sides 25.25
Rear both sides 27.25
Rake looks great…not too pronounced but noticeable. Looking forward to seeing with trailer load.
Ride and handling are extraordinarily better and different. Really thrilled with the result and the effort.
Still sitting on 16” wheels/31” tires. Doesn’t even look all that bad. Did land a pair of 2004 HD 18” wheels that I’ll add whenever it needs new rubber
This was after over a year of reading threads all over this forum….what an education. This ended up going perfectly because I had done it in my head 1,000 times after reading all these threads . Huge help here…great resource. Gonna cross post this in a few threads that helped!
For me I was riding with maybe a 1/4" rake (rear high) due to the soft front springs (maybe 3/4" of clearance for the bump stops). The V code fronts only would have had me way too high in the front. The Modded B's gave me a level stance, but was still a little too soft on the rear when towing (I'd have maybe a 1/2" rear down rake when hooked up).
I added the air bags and when not towing I run them at 15psi...when towing I run them at 65psi (they max at 100). That 65psi raises the hitch ball exactly 2" which is immediately sucked up by the tongue weight of the trailer, so the stance is exactly the same as when not towing.
Had I not done a Modded B and went how you suggest (using bags to make up the difference), I'd be running my bags at 100psi and maybe still having a little bit of sag.
The air bags SUCK if used to simply gain height. I rode them with no trailer at 35psi to see what it felt like and the rear end was filled with helium, bouncing all over. At 65psi without a trailer it felt downright dangerous. They are WAY too "bouncy"...makes the rear end feel like it's a clown car on huge soft tires.
The modded springs give you height AND stiffness, where the un-modded springs and blocks give you height only. I can't imagine towing with just the B's and bags...I'd be maxed out and hoping the road was in a good enough condition. The modded B's plus bags give you a LOT of 'safety margin' on the rear suspension.
I can't speak enough to the V/Modded B setup...the B's will be stiffer than stock but in my opinion are still not stiff enough if you tow heavy.
The Modded B's (again, my opinion) are just about perfect for towing the average load - a small trailer, average boat, light travel trailer, etc. Adding the bags will let you tow pretty damn heavy and still not have a dangerous rake - stiffening up the rear end and helping keep the truck level...adding a little weight to the front which is always good when towing.
I'm getting ready to do my rear springs. Glad we can keep an 11 year old thread alive! Anyway, I read this whole thing. I wanted to agree with Robert here. I put SD Springs "X Codes" on the front of mine. (HUGE improvement) I decided to try and be slick and add airbags to make up the height difference. A little cheaper and easier, right? It is in fact bouncy and I don't like it. I have to keep 45 psi in them to make it look right. After thinking more on it, I sort of installed a hack air suspension with crappy leaf springs for a fail safe...
My springs are so shot it sits on the snubbers all the time without air in the bags. I had replaced the snubbers because the old ones rotted off and I thought Ford put them on there so I need them. After I replaced them I got a noticeable clunk and ride harshness from the rear with out air in the bags.
Anyway, thanks everyone for all this information! I'm, ordering springs shortly...
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