Ultimate long haul rig

[D-man]

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I am in need of some advice for a project I am working on. I have a customized 1991super duty with a zf5spd, 5:13 gearing and a n.a 7.3 idi.
I had high hopes for this truck after getting a great deal on it. I travel constantly in the summer for work and pull a 20ft loaded trailer with me. I think it would potentially make an amazing long distance tow rig. The sleeper,dual 50ga tanks, and flatbed were perfect for what I needed. However, the 5.13 gears, very weak power, and hard starting issues (would only start when cool with ether)were not. As a result this project has sat for a year while I worked on other more pressing projects. Now I'm ready to either make this happen or scrap the idea completely.
My goal: have a dependable running tow vehicle, that has good power & can cruise at freeway speed when empty or lightly loaded. Without spending tons of $$!

My tenative plan: install ats turbo (I currently have) onto existing motor. Install a gear vendor overdrive (I know where a used one is), to help out with the low top speed.

Other options : I have another used 7.3, I pulled from one of my other trucks, I could build it up moderately(pump injectors, cam)? And swap it in?
Or look for an older cummins to try and swap in?
What would you do?? Suggestions please!

 

[Waystro]

First Welcome to the forum.
Second we need better pics.
If your looking for highway speeds I'm thinking a 12v with 3.55 gears
should net what your looking for.

 

[riotwarrior]

Welcome

Tons here on hard starting

You got a great tow rig NOT designed for speed however it is designed to not stop...if in good conditon.

How many miles on rig?

Starting poorly is air intrusion or glow plugs or ip or low comp....kinda need know more before say much

Read stickies abd search for info on glow plugs abd air.

If u do a mild build that would be sweet ride.

Comp test along w leakdown test tell u plenty on engine.

Like the ride I do!

 

[catbird7]

Will that rig require you to have CDL?

 

[IDIoit]

wow. this is the first medium duty rig that ive seen that i like stacks on.

leave the rear gears alone and run a splitter?
depending what you tow.

if you tow long distances, i personally would build another engine and swap it once done.
then you know everything about it, and deletes the guess work.
thats a killer truck.

 

[D-man]

Thanks for the warm welcome! I've been reading this site for a long time before joining. I'm not sure if it showed up on my profile, but I also own several other idi's, and a couple powerstrokes, so I am somewhat familiar with these trucks.
Truck has around 250k on the motor. I have done the glow plugs,relay,batteries, and looked for air intrusions. Compression test was done, and all cylinders were strong except one was down a little.
IM confident after Going through everything again this spring I'll be able to get it starting easier. What I'm trying to decide is how to proceed with the gearing and power upgrades. It's a pretty heavy truck, so I'm not sure if the addition of a turbo, and gearing alone will be enough power to make it useful.
My other idi's are 3/4tons with turbos and 4.10 gearing, and have just enough juice to get the job done.

 

[D-man]

No cdl required in Idaho. Must be gvwr over 26,001.

 

[Clb]

First Welcome to the forum.
Second we need better pics.
If your looking for highway speeds I'm thinking a 12v with 3.55 gears
should net what your looking for.

I second this^^^
Running the road daily I 'd want the cummins in it.

 

[The Warden]

If your looking for highway speeds I'm thinking a 12v with 3.55 gears
should net what your looking for.

I second this^^^
Running the road daily I 'd want the cummins in it.

Regarding the 3.55 gearing...

I have a customized 1991super duty with a zf5spd, 5:13 gearing and a n.a 7.3 idi.

He has an F-Superduty a.k.a. an F-450, with a Dana 80 axle. Unfortunately, that limits his choices in gearing...I want to say it's possible to re:gear to 4.88's, but hopefully an F-450 expert (i.e. @towcat) will have a better answer. However, I know for a fact that 4.10 or 3.55 gears aren't available. The best choice for getting RPM's down would be a gear splitter...you can either get a Doug Nash/U.S. Gear gear splitter meant for a 4x4 and put it between the transmission and the parking brake assembly, or find a GearVendors meant for a transmission with a parking brake, or do a remote-mount GV (or get creative with a Brownie box ) along the driveshaft somewhere.

For that reason, I'd hold off on deciding which engine to go with until you've come up with a definitive answer on gearing/OD units and such. Reason being...honestly, if you want extra reliable power, I'd go the 12 valve route (I know that many consider that sacrilege around here, but that's my honest opinion). However, if you were to go that way, you really want to get your gearing set up so you're around 2000 RPM at your typical cruising speed. A little higher wouldn't be terrible although your fuel mileage would probably suffer some, but keep in mind that the factory governor on the 12 valve is 2700 RPM. You can put in heavier valve springs and a different governor spring to get the governed RPM up, but I wouldn't want to cruise that high.

JMHO...more pics would be nice, but offhand, she looks like a nice truck and the basis for a good project

No cdl required in Idaho. Must be gvwr over 26,001.

That's correct for a single vehicle, but what about for a combination vehicle? I don't know how it is in Idaho, but in California (and IIRC by federal law if you're running out of state, but I don't have a CDL book with me at the moment), you need a Class A CDL if you're towing a trailer over 10,000 lbs even if the towing vehicle weighs less than 26,000 lbs. How heavy are you planning to tow?

 

[79jasper]

While I would get a splitter, Yukon gear does offer a wide vary of gears. https://www.yukongear.com/partslist...e=RWD&DiffID=274&DiffName=Dana+80+-+37+Spline

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[The Warden]

While I would get a splitter, Yukon gear does offer a wide vary of gears. https://www.yukongear.com/partslist...e=RWD&DiffID=274&DiffName=Dana+80+-+37+Spline

I recall there being something about the internal carrier that limits the ability to use axle gears taller than a certain amount in the Dana 80's used by Ford. Note that the second 3.73 gearset listed mentions that it's thinner and meant for a 4.10 and up carrier. Again, I don't know enough about the internals to say with any certainty, but I would suggest that the OP be cautious and do his research before spending the money on a gearset. People who have dealt extensively with this axle have said before that gears taller than 4.63 are a problem...if the taller gears on Yukon's website will work on an '88-'97 F-450 Dana 80 without breaking the bank, there will be quite a few F-450 owners who will be very happy at this news

Here are a few threads worth looking through:

http://www.oilburners.net/forums/showthread.php?43561-Dana-80-gear-swap-to-4-10
http://www.oilburners.net/forums/showthread.php?38573-need-help-with-finding-a-gear
http://www.oilburners.net/forums/showthread.php?41216-F-Superduty-Dana-80

 

[riotwarrior]

Brownie box is an option too...and a damn good one...gets u under direct over...so bull low to taller 5th gear...

A stroke swap isnt hard if u cqb swap w engine...done it before...was stupid simple.

Bottome line all depends on what is important to you.

Ip turbo and IC could go a long way to making it go and tow...gearing makes it better.

Qdd yer trucks in yer sig btw please

JM7.3CW

 

[D-man]

Great advice! 12v would solve any Power problems, but I'm afraid would be $$, and a difficult conversion. I would love to use this existing 7.3, but have my doubts about being able to squeeze enough power out of her. Exhaust should be up to par, I would just need to focus on fuel and air intake/turbo.
Approximately how many lb ft, can one gain from a regular ats turbo, bigger fuel pump, and maybe intercooler?

 

[crash-harris]

With such low gearing, I would think that some freshening up to get the IDI happy should do you well. Won't win any races, but won't stop untip you want it to. My 300 gasser is the same way. Before I grounded Bruiser, she was pulling herself and twice her weight. Engine refused to be held back by these "motor mount" things, but wouldn't give up engine speed even on a 8% backroad grade, no run up

 

[Blind Driver2]

Ditch the sleeper and drop on a pop up camper.

There are a wide range of gear ratios available.