In a world where I can change water pump and thermostat in 30 minutes, with a smoke break added for the heck of it.
The IDI is slow and heavy, not to mention a fat pig that is difficult to work around.
Sure, a turbo helps the slow part, but complicates working on it.

Factory IDI/5 speed trucks come with 2 things I dislike. Plastic headlights and ball joint I-beams. I really dislike the 87-91 nose. I'd rather not have to look at that ugly thing. If I were to get any IDI/5 speed truck, I'd hunt for the uber-rare IDI-T/5 speed. But, I'd still have to deal with the cramped engine bay.......

 

I-beams can be swapped in just a few minutes......

 

i've worked on several PSD's with well over 400K on them, and heard of plenty that went 800K-1M or more.
Of course, there's also the 24V Cummins that comes in to the shop about once a month. Shows 830K, on it's 2nd way around.......... The ABS system was unhooked for about 2 years (prolly 200K) when he brought it in to me the 1st time. I found the RF ABS sensor wires were pulled apart, resolving the ABS issues that caused him to unplug the ABS module...... That was ~3-4 months ago. It read 780K then. Yes, 50K in that short period of time.
He had in the shop yesterday for a clutch. He said the old clutch was *only* a couple years old. I had to remind him that 150-200K/year isn't quite the normal rate......

 

I get all that, there are a few things that are easier on the cummins, and given the same level of maintenance the cummins will out mile an IDI. I didn't bring this up as an IDI vs 6BT thing, though I still choose IDI, but as an is it worth it thing. If you had said your goal was a truck to pull 30K back and forth across the country and you're putting a cummins and NV4500 in an F350 that would be one thing. But your not, your goal is to try and save money and your putting it in a F150.

FWIW you know IDI's came in bullnoses, just no 5 Speed, that said it's a much easier/cheaper and to me much more practical upgrade to a IDIT/ZF5 then a 6BT/NV4500. Or, drop a bullnose front clip and bed on a later truck. That's all I'm saying, I just don't see how it fits your stated goals.

Ohh and if you think your going to get anywhere near 30MPG that will take some aero mods. Which of course would be better with a more aerodynamic front end to begin with, so the 92+ wins there.

 

How many spare parts do you have that are common just to the f150's? I think I read you had a spare frame? Pedals and all that stuff are common to the f150 and the 250/350's. It would be easy if you could round a f250/350 up, to slip a f250/350 frame under your f150 body. The only reason I am siding with the other guys on this is the heavier rearend. And you will get to use the better 16" truck tires as well. Of course you will need new 8 lug wheels.

 

The Ford 9" is capable of handling the output of the cummins. Heck, they've been used by the GM drag racers for years, as GM doesn't have a rear axle that take this kind of abuse.
I'm not looking to drag huge loads around, either in the bed or behind the truck. If I need to do that, I'll borrow the boss's F350SD that has had the sick-o pulled, and a 5.9L dropped in.

The simple truth is, I have wanted a diesel powered pickup for years (even before you could buy a new one) but I don't want/need a 3/4 or 1ton truck. The Cummins is, hands down, the best diesel ever offered in a pickup, it just happened to offered in a dodge, which I don't want.
Truth is, many people that have owned both older 5.9 trucks and newer 6.7 trucks, wish they still had the 5.9. Most of them replaced older trucks due to the truck falling apart, not because of engines that were worn out.

I have considered finding a F250/350 frame and suspension, and it *could* come down to that.
As the "better 16 tires" part, I could do already. Dodge 1500 wheels fit the F150, and they are 16", plus there are many aftermarket wheels available in 16".

 

Different truck is not happening. Don't want any more suggestions in that area. Telling me to get a different truck is no different than someone telling you to sell your kids/wife/dog and get a different one(s). We've spent 16+ years together, no need to change.

Different chassis *could* happen, most notably, if I were to find a 4x4 chassis with a D60 under the front. Even that would be questionable.
I have no doubts about the suspension and brakes holding up, since the IDI and PSD swaps are common in Bronco/F150 4x4's, and the king pin I-beams are way stouter than the ball joint D44 TTB or solid axles. The 9" will also hold up fine I'm sure. Just because I plan to build the engine to be *capable* of making ~30 PSI, doesn't mean I intend to use that much boost. Heck, I've never even matted the pedal on the current 300 in the last 15 years. The one time I did, shortly after buying the truck, was to pass a car on a 2 lane hiway, and the pedal got stuck on the floor mat. Same mats are still in the truck....... Plus, my daily driver is a 2.3L 5 speed "ranger" with a 3.45 rear axle. That will never win a drag race, but it can (and has) tow a car 50 miles. This will likely be sold, after the Cummins conversion is completed. My son wants it, to do a 4BT swap........ (also rather common)
I leave the WOT stuff on the track, where I use it on a regular basis in both the RX7 and CRX.

 

Well, I would not swap the frame because it had the holes in it. I abused my 1980 pretty good and never had problems with the frame in that area, only the other areas and crossmembers that rusted out.

If you are going to use this 1/2 ton pickup like a 1/2 ton pickup, then I think you will be fine. If you break something, then I guess it will be plan B

 

I do have a set of pedals loose it turns out. Looks like they may have come from pre-hydraulic though. Probably could weld a pin in it and be fine.

 

That is the kind of info I was asking for. I never subscribed to the theory that the holes made the frame less structurally strong, though I do know they make it buckle at the holes in the event of an impact (crash), of course any impact severe enough to do this, would bend any other frame as well.

Yes, it's going to be used like a 1/2 ton, just like it has for the duration of my ownership.
It certainly won't be seeing the kind of abuse that many diesel owners give their rigs. You know, when they stand on the brakes, mash the throttle, and see how quickly they can destroy the rear tires, brakes, axle and auto trans by turning them all into smoke....... I got over the smokey burnout thing more than 30 years ago. Even then, it was in a stick, where the brake pedal was not used to make it look more impressive (rediculous)......

Trans choice is not set in stone. Stick is highly preffered, and the NV4500 is the top choice. Sure, there are other trans that will work just as good, but many of these require a rather pricey aftermarket rear cover for the engine, which adds another ~$700 to the cost of using them. heck, even the Getrag 5 speed used in early (89-93) cummins powered trucks would hold up far better in this application than it did in it's original application.
A ZF5 (460 or diesel) would be much easier to fit, since the crossmember would only have to be relocated, and the driveshaft shortened a bit (Cummins has to set the trans back 2", or the fan won't fit between radiator and engine).

For rear axle ratio, I'm thinking 3.25 would be the best all around choice, though a 3.00 or the current 2.75 should be capable of returning even better MPG. At least the 2.75 would give me the option to ignore OD while towing, without turning the engine higher than I would like. 65 MPH is just shy of 2000 RPM. In OD, it would be down around 1400-1500. Good for MPG, but not so good for towing........

Towing would entail ~3500-4000 LBS combined load, since my cars weigh 1800 LBs (CRX) and 2350LBS (RX7). It would rarely, if ever, exceed that.

 

Double check the powerband of the Cummins, I thought it was pretty low, much lower than a v8 diesel. Hopefully you can find something about it on the web and then make a more informed decision on the gearing

This is the only thing I am afraid of with the rearend. I don't know where you live, but if you have any mountains and long pulls, you are going to press that throttle down, and that cummins is going to respond. Pulling a long hill at a decent rate puts a lot of load on the rearend. A guy I work with pulled a 30hp tractor up and over a mountain near me, and smelled something afterward and found he could not hold his hand on the rearend it was so hot. The fluid was normal. He has a 96 f250 with the zf 5 speed and the 460. But I might be a worry wart and it will be fine.

 

Exactly that is the biggest weakness of the 9". With the third pinion bearing and low pinion location creating a lot of oil shear it quickly overheats with a constant load. It will handle the weight that the F150 suspension can handle, and it will handle the torque of the limited traction available in this setup. But it won't handle the two combined for long, not without really good oil and/or a cooler.

 

I live in OK, where we don't even know what a "hill" is..... How do you think I managed to drag that ~8K load shown on page 1?

As for fluid, I planned to use 75W 140 Synthetic. Dunno whats in there right now, I spose whatever ford put in it in Jan 80........


Peak torque on a Cummins happens at 1600 RPM, and (stock) governed speed is 2700. Usable torque band is ~idle (~750-800) to ~2200. Any higher, and you're just wasting fuel and causing excess engine wear. They will go higher, and keep on pulling, but it's rather pointless.

 

FWIW I use and would absolutely recommend this stuff, Red Line Synthetic Oil - Gear Oil for Differentials - Heavy ShockProof®

Real pain in the **** to get in though, stuff is sticky and THICK when cold, but it's weird it slips on itself really well, odd stuff, hard to describe. When the time comes I'd fill the housing with it before putting in the 3rd member.

 

rather good stuff, but quite pricey.....
We keep a high quality diff fluid in stock at the shop, I'll probably just use it. Unless I get another 2 gallon jug of the stuff I used in the trans/diff of the RX7. This stuff already had the needed LSD additive for the RX7. I tend to throttle steer this car when running an autocross. They are known as "tail happy" anyways, so I use it to my advantage.....

That reminds me, I need to add a drain plug to the rear axle housing. Dunno why Ford didn't do this. The 9" is a pain to drain, the first time.......