Chassis compatibility question

Hi All, one of my long term goals for my 81 SWB flareside is to convert it to 4WD (please don't tell me I should have just bought a 4WD truck in the first place). I'm not entirely certain of the chassis it currently has. The VIN on the cab decodes as a 81, but it does not have the swiss cheese frame, and I cannot locate a VIN on the frame, despite having looked several times. For the sake of this conversation, let's assume it's an 82-86 non-swiss-cheese Gen 7 frame. Or maybe it's truly an 81 and not all 81's were swiss cheese, I simply don't know.

So with that in mind, I have been watching FB marketplace, Craigs list, etc., for 4WD donor vehicles. Here's where my familiarity with the truck gets a little thin. I think a donor vehicle from 80-86 would be completely compatible. And I don't think they changed the chassis much from 87-91, so I'm guessing that a donor from those years would work too. After that, I'm unsure if the chassis changed substantially. I see a lot of parts that say that are compatible with 80-96, so is a chassis from 92-96 going to be a suitable donor vehicle? What about Bronco's - is is basically the same chassis and should swap over easily? What years of Bronco's?

I am mostly concerned with things like the chassis mounting point for the trans cross-member, suspension mounting points, and things like that. While I'm on that subject, what's up with some trucks being upper/lower ball joints, and some being kingpin? Mine happens to be ball joint, but what trucks came with kingpins? F250 and above or something?

Is it a requirement that the donor vehicle also be a SWB truck, or will a LWB truck work and it's just a matter of shortening the rear drive shaft?

Anyone out there done this? What are the potential pitfalls and gotcha's?

Thanks!

Kingpin trucks are as follows:

1980-1981 F100
1980-1981 F150 4x2
1980-1986 F250 4x2
1980-1986 F350 4x2
1986-1991 F350 4x4

Everything else used ball joints.

1987-1991 trucks used an almost identical frame to the 1980-1986 trucks. However, the front bumper mounts differently on the 87-91 (they mount to the side of the frame rail via angle brackets) and I've seen some 87-91 frames that do NOT have the slotted holes in the front of the frame rail for the 80-86 style bumper. I have also seen some 87-91 trucks that do have both sets of holes, so just keep it in mind.

1992-1996 frames have different front frame horns, and are not at all compatible with 80-86 bumpers. Rembrandt, a member here, used a 92-96 frame on his 1980 F150. He grafted the 80-86 frame horns onto the newer frame.

salans7 wrote

Kingpin trucks are as follows:

1980-1981 F100
1980-1981 F150 4x2
1980-1986 F250 4x2
1980-1986 F350 4x2
1986-1991 F350 4x4

Everything else used ball joints.

But, my truck is (ostensibly) an 81 2WD, and does not have kingpins. So is that proof that my frame is not an 81?

Bumper mount concerns aside, are the 92-96 suspension, engine and trans mounting points the same as an 81 (or maybe an 82-86)?

Pete Whitstone wrote

salans7 wrote

Kingpin trucks are as follows:

1980-1981 F100
1980-1981 F150 4x2
1980-1986 F250 4x2
1980-1986 F350 4x2
1986-1991 F350 4x4

Everything else used ball joints.

But, my truck is (ostensibly) an 81 2WD, and does not have kingpins. So is that proof that my frame is not an 81?

Bumper mount concerns aside, are the 92-96 suspension, engine and trans mounting points the same as an 81 (or maybe an 82-86)?

If I remember correctly (it's been years since I was reciting this info on another forum), the swiss cheese frame was a mid-year change out in 81, as were the kingpins. I think it's definitely possible that a late build 81 could have a traditional frame and ball joints. For what it's worth, the vin on my 1980 F150 was stamped on top of the frame right near the heater box. It was in the same spot on my 1986 F250 parts truck.

Engine, transmission, and suspension mounting is basically the same from 80-96 when it comes to the 1/2 ton trucks. So no worries there.

I 4x4 swapped my 1980 F150 using 1995 axle halves, 1984 steering knuckles and spindles, a 1982 transmission crossmember (4x4 crossmembers are different than 4x2), and 1989 axle shafts. Everything worked together without issue.

I remember going through this with somebody else not all that long ago, but I think the 2wd changeover from kingpins to ball joints happened in the last production month of the 1981 model year, so it is possible to have a ball joint front end in an 81, IF it was built in the last month. I think…

Do you have the stamped steel I-beams? Are they hollow? Or solid?

Front bumper issues aside, yes the 1992-1996 frames are basically the same as 1980-1991. I had to drill a couple extra holes for the rear most mounting bolts of the Flareside bed, but that was about it.

Rembrant wrote

Do you have the stamped steel I-beams? Are they hollow? Or solid?

Thanks for the info, guys!

The I-beams are solid, they appear to be a forging. What does that tell us?

I think I remember seeing somewhere when shopping for ball joints about an 8/81 cutoff, so I think there may have been a very short window in the 81 model year where ball joints were used instead of kingpins.

One donor truck I am looking at is a 95, it has a 351W (which I think would be a hydraulic roller motor), and what the ad describes as a "4D03" transmission - I think the seller means an E4OD. So that is an electronically controlled C6 with an overdrive, as I understand it. My question there is, is the trans controller separate from the engine controller? In other words, can I plug that transmission behind my carb'ed 351W running the trans controller only? If they are all one unit, I would either have to run the full 1995 engine/transmission package (I'm not entirely averse to FI), or see if someone makes a stand-alone controller for that trans. Any info appreciated there.

I'll let the others continue to answer questions re the suspension, but the E4OD's controller will be the EEC computer that also runs the EFI.  So unless you are going with full-blown factory EFI then I don't think that is the controller for you.

I've heard you can run the factory EEC from a diesel truck, I think for a 7.3L which wouldn't have had any/much electronics.  Or you can go with an aftermarket controller, like a Baumann, but they cost ~$750.  Having said that, I think the E4OD is a big improvement over a C6 as it has both the overdrive and the lockup torque converter.

Gary Lewis wrote

 Having said that, I think the E4OD is a big improvement over a C6 as it has both the overdrive and the lockup torque converter.

Yeah agreed, my mileage is pretty miserable, somewhere around 10-11. I thought that was low, but I looked it up and that's pretty much what they were getting in 1981. The 95 I am looking at shows 14/18 with a combined rating of 16. That's probably about what my 2006 F150 with the 5.4 gets. So would definitely consider swapping the entire drivetrain. I bet the 95 version of the 351W was putting out better power/torque numbers as well.

With the donor it shouldn't be too bad.  And you can't beat EFI.  Even if the '95 is EEC-IV it would still be much better than a carb.

I have a 1995 frame in my 1980 Flareside. The Bullnose front bumper swap has been done a few different ways, but I personally chopped the front ends of the 1995 frame off, and welded in Bullnose frame "horns" to mount the front bumper:






The only other issue I ran into was the very tail end of the frame only has one set of holes for the bed, and the Bullnose frame has two sets of holes (the second set is only for the "old" Flareside bed, which didn't exist in 1995). I drilled the extra two holes and bam, done.

There was also one small "flare" I will call in the 1995 rear most crossmember...I don't even know what it is for, but it interfered with the Flareside bed rear sill. I gave it a couple smacks with a hammer and made some clearance...haha...the frame, not the bed.

So my truck is a 1980 F150, with a 1986 300 inline six, sitting on a 1995 F150 chassis with the 1995 5spd, axles, differentials, etc.

Rembrant wrote

So my truck is a 1980 F150, with a 1986 300 inline six, sitting on a 1995 F150 chassis with the 1995 5spd, axles, differentials, etc.

All great info, thanks.

Can you tell me what drove your decision to swap the entire chassis? Was it the swiss-cheese thing, or would you have done it even if you had a later chassis?

My thoughts so far were just to swap the front axles, engine (possibly), trans and transfer box into my 81 chassis. So I'm not sure if you went the way you did because it was less work, or for some other reason. I'd rather listen to someone who's been down the road, than gain my own experience the hardest way possible. :)

I agree, the 95 351W should have roller valve lifters.

It has been my experience and my opinion that the E4OD behind a lot of power and torque should be beefed up. Had one in a 94 F250 with the 460. Having said that the E4OD in my Bronco has been trouble free.

With my fuel injected 351 I’m getting around 15 MPG on the highway. I really like how the Bronco performs with the 351W and the E4OD. I would like a truck with the same combo.

Pete Whitstone wrote

Rembrant wrote

So my truck is a 1980 F150, with a 1986 300 inline six, sitting on a 1995 F150 chassis with the 1995 5spd, axles, differentials, etc.

All great info, thanks.

Can you tell me what drove your decision to swap the entire chassis? Was it the swiss-cheese thing, or would you have done it even if you had a later chassis?

My thoughts so far were just to swap the front axles, engine (possibly), trans and transfer box into my 81 chassis. So I'm not sure if you went the way you did because it was less work, or for some other reason. I'd rather listen to someone who's been down the road, than gain my own experience the hardest way possible. :)

I can't speak for his reasoning, but swapping the axles and 4x4 parts into your current truck is much easier than swapping the body around. If your frame is in good shape, and you have a complete parts truck, just bolt in the stuff you need. That's the nice part about the half-ton trucks, they're plug and play when it comes to the 4x4 swap. The 3/4 ton and 1 ton trucks are a different story.

Pete Whitstone wrote

Can you tell me what drove your decision to swap the entire chassis? Was it the swiss-cheese thing, or would you have done it even if you had a later chassis?

The truck did have the Swiss cheese frame but it was rusted badly, broken, and bent. I simply wasn’t worth fixing. The 1995 chassis I bought was also rusty, but less rusty lol. I cleaned it up and repaired it.

As Shaun says, it way easier to swap the 4x4 gear and drivetrain imho that to swap the whole frame/chassis.

I dont see what the big deal is with the Swiss cheese frame?
Maybe they did not use them on 4x4's back in the day but will you be using it to plow snow with or heavy off roading and jumping it?

I am thinking not so if the truck you have now is in good shape but want it 4x4 whynot swap in the 4x4 parts from the same model 4x4?
They say the parts will bolt in.

If you start swapping cab & frames you run in to issues with VIN's as the cab has a VIN and the frame has 1 to match it.
Dave ----

FuzzFace2 wrote

I dont see what the big deal is with the Swiss cheese frame?

I am thinking not so if the truck you have now is in good shape but want it 4x4 whynot swap in the 4x4 parts from the same model 4x4?
They say the parts will bolt in.

If you start swapping cab & frames you run in to issues with VIN's as the cab has a VIN and the frame has 1 to match it.
Dave ----

Swapping the 4x4 parts onto my existing chassis is pretty much what I intend to do. I am picking up the 95 tomorrow. My 81 does not have the swiss cheese frame, so that's not an issue for me.

I have always wondered what the "official" VIN location is. I'm sure it varies by state, but is the VIN (and therefore the title of the vehicle) attached to the windshield plate, or to the chassis, or what? In other words, what can you swap without running afoul of the law? I have always assumed the official VIN plate was by the windshield and all else is swappable, but I don't know.

The VIN has been in the same place on Ford truck frames for years... It's on top of the RH frame rail, near the firewall. On some later frames. it's stamped pretty lightly, and in a dot-matrix fashion, so be careful cleaning it off! It is also an abbreviated VIN on later trucks, not the full number of the truck it was originally built with.

If you can't see it, grab a flashlight and a mirror - sometimes it's just rearward of the firewall and darn near impossible to see!

OK, I got the 95 truck home, it's in extremely rough shape body-wise but I don't really care about that. The 4x4 bits I need are all there.

Which brings me to a general question about 4WD. I had intended to keep the 9 inch rear that's currently in my 81. The 95 has an 8.8". It occurred to me that the ring/pinion ratios on both the front and rear pumpkin had probably better match, or one end was going to be faster than the other. I don't know what ratio's are in either truck, but am I correct in assuming that the front and rear need to match?

So, ratio question aside, is there a good argument to also swap in the 8.8 rear axle here? The general consensus seems to be that the 9 inch is stronger, but I don't absolutely know that's the case. I do plan to upgrade the rear drums to disk at some point, does one axle have an easier/cheaper path to do that than the other?

Thoughts welcome. Thanks!  

Yes, gear ratios need to be the same front and rear, or else the transfer case may develop holes.

The 9" is regarded the stronger of the two, because of the housing design, bolt in axle shafts, and bolted pinion housing. The 8.8 features c-clip retention for the axles, and they are okay for occasional off-road, but hardcore off-roaders and racers with 8.8's despise the c-clips because they tend to break or fall out under harsh loads. Both axles have aftermarket support for disc brake swaps, but neither is budget friendly.

If the gear ratio in your 9" is similar to the 8.8, leave the 9". If the gear ratio in the 9" is not the same, you'll pay a pretty penny to re-gear the 9" (really any axle honestly). So if the 8.8" is in good shape, it would be cheaper to throw that in the truck.

Pete Whitstone wrote

I don't know what ratio's are in either truck...

The 1995 will more than likely have 3.08 or 3.55 gears. By the time the 8.8 diff started being used in 1983, they will almost always have one of those two ratios. There's more variance in the 9" rear ends, especially in the earlier 1980-1982 Bullnoses when they were trying so hard to improve the MPG...2.47, 2.75, 3.00, etc. The 9" rear diff was still used alongside the 8.8 up until at least 1986, maybe later, but it was only in specific trucks...2wd with 351, and 4x4 F150 with 302 and NP435, and maybe a couple others. So in the later 9" diffs, you'll likely see 3.00 or 3.50 as the common ones.

By the way, one issue with using the 1995 F150 drivetrain, you will have nowhere to connect a factory speedometer cable, just FYI. Maybe this was discussed already? The way I'm solving this issue with my 1995 chassis swap is that I bought a transfer case out of a 1990 F150 4x4. It is the exact same BW1356 transfer case, but it still has the speedometer cable drive (1991 was the last year).