Seventh Gear!

[Big Dave]

1310 RPM @ 70 MPH indicated.

Its weird what you can hear when the engine isn't roaring so loud.

Zero toe-in and camber makes the truck a bit twitchy. It feels like a crosswind in dead calm.

[JasonG]

I wish I could afford that GV rear bob.
I'm running on 4.10:1. Talk about reaching for a 6th gear on the highway.
I have a taller set of tires I put on to get the rpms down. They help but I got lazy once and left them on while towing. Lets just say the hills weren't much fun and I was glad I had the granny gear.

On the twitchy part, try a stiffer steering dampner. (The shock bolted to your steering arm) The ones for big mud tires are stiffer. It will make for nicer towing as well, less arm fatigue.

[Frank Lee]

If caster is adjustable more of it should help.

[MechEngVT]

Originally Posted by Big Dave

Zero toe-in and camber makes the truck a bit twitchy. It feels like a crosswind in dead calm.

That's why nominal toe is usually slightly toe-in for RWD vehicles. Sure, zero is "in-tolerance" but a slight static toe-in allows for dynamic loads and bushing compliance without losing the on-center feel.

A stiffer steering damper (if you even have one) won't reduce twitch due to inadequate toe-in as that feeling is a result of variations in tire grip from side to side pulling the truck in the direction of the tire, not due to motions within the steering linkage.

Higher caster angles (and stiffer dampers too) increase steering effort. More caster increases the return-to-center moment due to increased trail, but if your "center" is toed-out under driving load your twitchy handling may continue even if slightly diminished because your tires will still point away from center. As your weight shifts to the left the truck will pull left and vice-versa, plus it should follow road crowning pretty strongly.

[gascort]

Originally Posted by Big Dave

This mod is pricey, but in my view this truck is now a form of hot-rod and not just some weak "duct tape and coroplast" dabbling.

Haha I think this is pointing at my car and other similar ones around here lol.
congrats on doubling the normal MPG of your truck - I consistently use you as an example to my brother and other HD truck driving friends.

[Big Dave]

Having driven it some, I think I'm gonna live with it as-is. It isn't THAT twitchy, just more than it was. The long wheelbase stabilizes it a lot.

The upside is my coasting distances have gone berserk. On a 0.6 mile coast from 70 to a stop light, I used to just coast up to the stop light. Now I'm going 40 MPH at the light and have to jam on the binders. Hence, next time I start my coast farther out. This is with my tires aired down to 80 psi. Before I was at 100 psi.

With two drive shafts there is a small amount of increased drive line "snatch" but it is managable and I'll smooth it out in a week or so.

At speeds under 65 MPH, my engine is now normally aspirated - zero boost.

EGT stays in the happy zone: <600 degrees F (pre).

The truck's whole acoustic signature is different with the roar of the engine attenuated. I can hear a front wheel bearing just beginning to rumble.

[slowmover]

my coasting distances have gone berserk. On a 0.6 mile coast from 70 to a stop light, I used to just coast up to the stop light. Now I'm going 40 MPH at the light and have to jam on the binders. Hence, next time I start my coast farther out


Can it coast all the way across Illinois?


I, too was wondering about the steering affect (alignment witchery).


At speeds under 65 MPH, my engine is now normally aspirated - zero boost.

EGT stays in the happy zone: <600 degrees F (pre).


Wild . . . .


We gonna get some weight stats (empty and loaded) for a range? Curious minds want to know . . it currently weighs 7,900-lbs, and generally ranges to over 9,000-lbs?


I've been wanting to come to TX to talk aerodynamics with the guru.


North Texas would be about half the distance from Indiana to South Texas. Better charge the A/C back up if it isn't between November and April.

Keep it coming. I hope you'll think on doing some video. A-B per cab noise would be cool. As would some shots from other cars showing how far that thing can roll. I'll have to break some rules about cheering for Fords.

.

[Big Dave]

I don't think I can coast across whole states. It ain't a 12,000 ton train rolling on steel wheels/rails, but I'm still adjusting my coasts.

Truck curbs at 7,600 lb and GVWR is 9,900 lb. I'm running empty right now.

Astonishingly to me, despite the huge overdrive ratio and tall final drive, this thing still can accelerate at 70 MPH in seventh gear.

[Big Dave]

I always thought my OEM Firebombs were pretty quiet.

Now without the engine roar @ 70 MPH, I can hear them howl.

Sure wish somebody would update the LRR tire list.

[elhigh]

Man do I envy this whole thread.

It's no powerlifter and frankly East TN is really pretty hilly, but my old Yota has the twist to turn a sixth gear, hills included. The speedo is so far off, it's exactly right for if I was running a 3.35 rear, but I'm pretty sure the 3.73 was always the right ratio. But an extra gear up top, boy that'd be good.

Kudos, Dave - I'm really looking forward to seeing how this turns out.