Grumman LLV Mail Truck

[Dtc81]

Yep. It's a mail truck! A Grumman LLV if you wanna get technical...This is going to be my best attempt to build my "dream" truck. I have always wanted to turn one into a quirky "do-it-all" unit. Something that can hold its own on the rocks, be safe and capable at speed, go down the road straight, and haul the family for short fun runs.

Current Parts Spec:
Engine: GM LQ4 6.0L
Trans: 4L80e
T-Case: Ford NP205 with ORD Magnum Underdrive
Front Axle: 2015 D60 with MoFab keyed high steer arms, Barnes truss
Rear Axle: Sterling 10.5 with Artec truss
Wheel/Tire: Sidetracked Off Road 17" forged bead locks, 40" KR3

Goals:
-Push my design, fabrication, and welding skills.
-Retain LLV charm: sliding doors, rear roll up door, general proportions, basic amenities.
-Have a little bit of race car vibe.
-Low CG, ideally flat bottom the whole thing. It's going to drag.
-Safe.

Backstory:
I spent nearly 6 years trying to track down a mail truck, and finally scored this one in 2022. I tried buying this LLV in 2019 when the owner was in Colorado, but he decided to keep it. Two years later I missed a FB message from him while I was at Fabtech. He sold it the next day. I found another, much cleaner LLV in Maryland, but the owner wanted a ton of money for it. He sold it, but the buyer mentioned he had an LLV in rough shape. We got in contact, both had wives due with kids any day, so tabled the sale until the newborn dust settled a few weeks later. After a 19 hour driving day I finally had my LLV.

Well, life took over for a few years, so it sat behind the barn while we were building a new shop. I was slowly buying drivetrain parts as I found them. I work in construction, and have a small welding and fabrication business on the side. (@dcbuiltllc on Instagram for those curious). This is by far the most extensive vehicle fab project I've done, so I'd love any criticism and feedback! I've been following a bunch of different social media accounts, YouTube channels, and forums for years now, trying to soak up as much knowledge as I can.

I started by building a simple chassis table out of some channel, and then dove into stripping the LLV. I knew I wanted to challenge myself with a full chassis build, so only the body was saved. I had a 2000 Chevy Suburban for a motor/trans donor. Stripped that, and kept all the misc./wiring, although I'm leaning towards a Holley Terminator or similar. I tore down the axles so I could properly pre/post heat them during the truss install. I rebuilt and repainted the NP205 and mated the ORD Magnum to it.

Current State:
As of this post (1/1/26), the body is on stands. The motor and trans are roughed out onto the chassis table, and the front axle is positioned. I need to cut some of the floor/firewall to drop the body lower, and further back.

I have some questions; hopefully people can drop some knowledge!
1) Is there an "ideal" starting location for the engine relative to front axle? Currently cylinder #1 is 6" behind the front axle centerline. I'd like to centralize the weight, but not to the point where the "step van" vibe is completely ruined by a big engine/trans tunnel. Driveline length is also a consideration.

2) Current plan is to mock up at full bump to see packaging/layout constraints. Layout linkage design and then work it to ride height. I have archived a bunch of old forum posts and online calculators to help guide me. Does this sound reasonable?

3) Is there a general rule for how much clearance should be between engine and axle at full bump? (Just a starting point number). Currently around 2" as is.

4) I'm open for options on suspension design - at a minimum, basic 4 link rear, but possibly trailing arms because they look fun to build. Probably 3 link front due to space. Plan to run a single 14-16"coil over at each corner. Would love to find more geometry and design info to add to my research if anyone has recommendations.

I've quickly learned this whole thing is a game of compromises! I'm enjoying the learning curve and know there will be lots of tack, test, cut, repeat in my future.

Photo Dump:



NP205 with ORD Magnum:

Sliding chassis table under body:

Engine location in relation to front axle:

116" Wheelbase for reference:

 

[Kellyex1450]

This is so rad! These are fascinating vehicles that offer a ton of interior space for their footprint. I think you’ll find it ends up being surprisingly practical beyond the initial novelty.


I’ll try to answer some of your questions — I’m not an expert, but hopefully this helps. hopefully others can drop some knowledge too.

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1) Is there an "ideal" starting location for the engine relative to front axle?
Currently cylinder #1 is 6" behind the front axle centerline. I'd like to centralize the weight, but not to the point where the "step van" vibe is completely ruined by a big engine/trans tunnel. Driveline length is also a consideration.

My thoughts:
In your case, you’re best aiming for where everything works for the build as a whole. You’re packaging a lot into a tight space, so it really comes down to what fits and functions best. Try to avoid extremes in either direction. As long as you’re not pushing the engine excessively forward or backward, you should be in a good place.

---

2) Current plan is to mock up at full bump to see packaging/layout constraints.
Layout linkage design and then work it to ride height. I have archived a bunch of old forum posts and online calculators to help guide me. Does this sound reasonable?

My thoughts:
That approach makes sense. First, decide on the link system style you want. From a packaging perspective, a 3-link with panhard bar front and rear works very well here. It gives you the most flexibility to juggle engines, transmissions, fuel tanks, and other components.


There are many DIY 3-link kits available from suppliers like Barnes and RuffStuff. Laying everything out with PVC for temporary links is a great way to mock things up — cycle it, cycle it again, and then cycle it some more. You can experiment with different link lengths and heights easily this way. As before, stay away from geometry extremes.

---

3) Is there a general rule for how much clearance should be between engine and axle at full bump?
(Just a starting point number). Currently around 2" as is.

My thoughts:
In race car applications, people sometimes run as little as 1/8" of minimum clearance between components — but that only works if you fully understand the maximum movement of everything involved.


In prerunners and similar builds, rubber engine mounts and suspension bushings allow more movement than expected. I think 2" is generally fine, but what makes a solid axle swap different from IFS is flex. With IFS, flex is essentially the same as normal up-and-down suspension travel. With a solid axle, the axle can actually move higher during full articulation than it does at straight-up bottom-out due to the angle it’s at.


Even if you have 2" of clearance at full bump, you may lose that clearance at max flex. Accounting for that is one of the more painful parts of solid axle suspension design.

---

4) I'm open for options on suspension design
– at a minimum, basic 4 link rear, but possibly trailing arms because they look fun to build. Probably 3 link front due to space. Plan to run a single 14–16" coil over at each corner. Would love to find more geometry and design info to add to my research if anyone has recommendations.

My thoughts:
Again, I think your best bet is a 3-link with panhard bar front and rear, with no more than 14" coilovers all around. If you run into packaging issues up front, a radius arm or Y-link front setup is also a solid option. Both offer excellent packaging flexibility and work well in tight builds.

---

Here’s also a great video on the history of the LLV!

https://youtu.be/edPqtHPiMMk?si=Snob7UDdSrAggbMD

 

[Dtc81]

@Kellyex1450 thank you! The 3 link up front will almost undoubtedly be my best option. Stretching the wheelbase to around 116 definitely helps in the driveline layout vs. what I would be up against if I kept it closer to the 100.5" stock WB. I need to figure out a fuel tank/cell soon too before the rear suspension layout starts.

You're right about the deceivingly large amount of space inside. Obviously needs to stay RHD, and I want to retain the swivel driver seat mount. I'll fab brackets so I can swap between the passenger seat and USPS parcel tray that I saved. (feel like having an interior picnic table on a solo weekend trip would be so badass!) For the cargo area I have this idea to use (or fab something similar to) T track on the floor, and build mounts for the rear bench seat and spare. It would allow some modularity. TBD if T track would be strong enough to retain a seat with passengers and a 40" spare in a crash or rollover. But I'll get to that.

Thank you again for the reply and info! Much appreciated.



Can see the interior tray in this photo from the day I brought it home. A LOT of pressure washing, degreaser, and bleach after this was taken.

 

[Turboyota]

Modularity would be badass.

T-Tracks hold airplane seats in place during crashes. There are different grades(strength levels), so track selection matters.

 

[smokeysevin]

Bonus points if you french the tracks flush in the floor. That would be a really clean install.

I have some between the grooves in my truck bed and they are just flush with the bedliner. I'm super happy with them and I can still load rocks and drywall and shit in there.

Sean

 

[Dtc81]

@Turboyota Nailed it! I noticed it on a flight once and thought it would be a really useful addition! I'll definitely do my research when the time comes.

@smokeysevin That's an awesome idea. The floor of the LLV is actually made from aluminum I beam extrusions spaced closely together, and the sheet metal body riveted straight to it. I have gotten very good at drilling out rivets already


So much room for activities! (until a seat and a spare get mounted.)

 

[smokeysevin]

Which way do the extrusions run? Along the driveshaft axis or along the axle axis?

Sean

 

[Dtc81]

@smokeysevin extrusions run with the driveshaft axis.

Good angle from the back:


Topside view from in cab. Motor is centered relative to the body in this photo.


Looking at the first underside photo; I want to chop out the floor enough to slam the body down over the bellhousing. The drop step/rockers will be low- but the plan is to build and integrate a minimal "slider" off the main chassis rail to protect them. The body itself is 6' tall overall, so any creative ways to keep it low (within reason) will be ideal.

I thought about chopping 10" out of the bottom step area and sliding door - but i think it will lose some of the step van feel.... lots of compromise!

 

[DP_Tundra]

Might be a dumb question or you already said it but will you be keeping it right hand drive?

 

[Dtc81]

Might be a dumb question or you already said it but will you be keeping it right hand drive?

Yes will be keeping it RHD