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Hey all,
I have strong intentions of buying a 71-72 J4000. It is suppose to have a 472 caddy/buick tranny swapped into back in th 80's. I will be wanting to update the drivetrain to more modern and I want an overdrive. Just off the top of my head, SBC/700r4/t-case comes to mind. Are there any articles out there covering this swap? It still want to keep it carbed and no computer. It has the Passenger drop front. My end goal is a DD with AC and comfy ride in near stock suspension form

There is all kinds of information in the build section. Pretty much every body goes with tbi to get the most out of the engine tranny modernization

If you go SBC, you can transplant all the EFI stuff with the engine. Not difficult. Otherwise, you throw away much of the advantage of swapping. Does not make a lot of sense to convert a modern engine back to an obsolete, inefficient and troublesome carburetor.

Another thing you will discover - your front axle is closed-knuckle, and you may want to swap axles too.

The t-case from a 350TBI GM truck will be drivers side drop, so an axle change will be needed. If you wish to keep the Dana 20, Novak makes a nice 700R4 to D20 adapter that ends up being about the same length as your current TH400 and factory adapter. But it's a little spendy.

As I understand it, there is a strong chance the rear diff is a Dana 60 5 lug? Concerning the closed knuckle-would a Dana 44 Open Knuckle be a suitable swap? It appears 70's Chevy/Dodge are the donors for passenger drop? Are there any write ups on changing to a driver side drop front that I can read and learn?
I really do not want to go to a fuel system that requires a computer...just my preference. I might just be better off rebuilding what's in it since I do not want the computer. I do appreciate the advice and ideas.

Hi -

If I weren't going to go with EFI, I'd just keep the drivetrain that I had. The Cadillac is a great engine, and the TH400 and Dana 20 that you have now are very durable and reliable. The main thing you'd be giving up is the overdrive automatic, but it would take decades of driving to pay back any advantage you'd get from converting to the overdrive transmission in place of the TH400.

Re the rear Dana 60-2, that's a fine and desirable axle. It's only problem would be with the brakes. The 12" drums have been unobtainium for a decade. It is possible to convert the rear axle to disks though, and then you'd have a fine axle and no brake problem.

The closed knuckle front is more maintenance and less durable than the later open knuckle axles, and the open knuckle gives you a tighter turning radius. But there's nothing terribly wrong with the closed knuckle axle, and it can be converted to disk brakes.

But don't burn that bridge until you come to it. If you have a J-4500, it will have a Dana 44 front and rear, and no parts issues.

That caddy motor is more modern a design than a SBC if I'm not mistaken. If you want over drive, why not build a 700R4 in a BOPC case? Then you could run a GM NP208 behind it. Or adapt it to your D20.

Or put a Buick 350 in it...

If it were me, and the Cadillac engine runs good, I would keep the Caddy engine and go with a 4L60E (the electronic version of the 700R4). Those Caddy engines are actually pretty good at fuel mileage, aa is the QuadraJet carb. With the torque of the Caddy engine, you should be able to take good advantage of the OD.

From what I was told, part of the reason the truck was parked was due to the motor burning oil and noise coming from t-case or differential. I am going try and make arrangements to pick it up 2/27 instead of 3/5. Getting anxious now, unless the frame has been hacked on or rust holes through, its coming to south Texas . I am pretty confident I will have the only one in my home town.
Good points on keeping the drivetrain and the point made on the cost to go OD vs keeping the TH400. I will be back asking more questions once I get her in the garage.

ProTouring442 wrote:If it were me, and the Cadillac engine runs good, I would keep the Caddy engine and go with a 4L60E (the electronic version of the 700R4). Those Caddy engines are actually pretty good at fuel mileage, aa is the QuadraJet carb. With the torque of the Caddy engine, you should be able to take good advantage of the OD.

The only BOP pattern TH700R4s I've found so far had the Olds 350 diesels in front of them.

carnuck wrote:

ProTouring442 wrote:If it were me, and the Cadillac engine runs good, I would keep the Caddy engine and go with a 4L60E (the electronic version of the 700R4). Those Caddy engines are actually pretty good at fuel mileage, aa is the QuadraJet carb. With the torque of the Caddy engine, you should be able to take good advantage of the OD.

The only BOP pattern TH700R4s I've found so far had the Olds 350 diesels in front of them.

True, but I cannot imagine there isn't an adapter to mate a Cadillac engine to a 4L60E (or even a 700R4, for that matter).

Now, given the info above about the Cadillac engine needing serious repair, I'd probably go LS series with a 4L60E. I know the OP said he wanted to stay away from electronics, but the new stuff is just so dang reliable. I love my LY5/4L60E swap.

If you're going TBI anyways, I would go 4L80E. I'm going to be doing that with my motorhome. I'll also be swapping in a TBI 5.7L that's in my '93 P30 ex-Seattle City lights work truck unless the noise in my 454 is just a bad fuel pump arm. Electric fuel pump got it running for first time in 8 years.

If your bothering with a EFI SBC, you should just jump straight to a LS instead. I don't think the SBC is worth the hassle. You can get 5.3l Iron block LS motors pretty cheap, and they get great gas milage in a wag.

If that was for me, I already own the 5.7 with 4L80E and have the service records with it, plus it has a hydraulic pump built in for running some accessories like a custom slide out and the 4L80E works well so it's a bolt in swap (I neglected to mention it's for my '82 Geiorgieboy motorhome with 50K original miles on it).