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D44 SAS with Cummins swap

51317 Views 171 Replies 69 Participants Last post by  86turbodsl
Hi - I'm building a 1990 f150 4X4 super cab with a Cummins 4BTA, D44 SA frt and 9" rear. This will be a pavement queen, 4x4 used for wet dirt roads and snow. I will be running Denman Coyote 305/85/16 since I want a tall, narrow tire for mileage and to get the overall ratio I want. I want minimum lift to allow the 36's plus room for the D44 SA. Rancho makes a 4" coil for the 1984 F150 with the 6.9L diesel. That may be a little heavy since the 6.9 weighs about 200 more (900) than the 4BTA (700). Will the 1984 coil mount in the TTB buckets OK? If not then I guess I can use a 2" TTB coil plus the coil adapters for the SA RA's which should get me close to 4" correct? Since
the 1978-79 coil buckets are no longer available from JBG I am going to try moving the stock TTB buckets forward 1" to get that extra clearance to the quarter. Am I on the right track here or not? Thanks.
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It sounds like you are going with the 79 coil buckets...good choice. However, it CAN be done with 78/79 coils and the stock 1990 coil bucket. That's what we did on my SAS, and it worked fine. We did modify the coil buckets slightly by welding a little tab in front of the coil to make sure it doesn't pop out, but it worked ok in the stock location. Although not the absolute best way to do it, it did work for me.

And good luck with the cummins build. I would LOVE to have a diesel under the hood of mine.
Cab coming off, POS TTB is out, frame to be sand blasted next then I am going to beef it up some.


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Cool doin a ground up resto. But only better.

I likey
Nice buildup! Like the idea of swapping in a Cummins.

You can order brand new 66-77 Bronco front coil buckets from They are a little different then the 78-79 coil buckets but will work. Plus they make them in two different heights.
52 Wrench, Good luck in the build. It's going to look great. I've been thinking of doing the cummings swap in my 96. Why did you decide on the 4BT and not the 6BT? Just curious. Will they both give good gas milage and power. Or is one better than the other? Thanks.
Huh...Hadn't seen this thread before. What tranny are you running with? You said it was a M5R2 which is a v-6 t-bird SC tranny. You mean a M5OD? You sure this is the best for this? I realize you are not going to do a TON of heavy wheeling, but they are not known for their toughness. Good build though...

Why did you decide on the 4BT and not the 6BT? Just curious. Will they both give good gas milage and power. Or is one better than the other? Thanks.
I know ya didn't ask me, butttt there is good info in the differences of the 6bt and 4bt.

Mainly weight, 6bt ~ 1000lbs fully dressed, 4bt ~ 700lbs fully dressed.

Power on a 4bt is usually around 100-130hp and up to 340tq stock. After tuning you can achieve more of course. Also if you browse you can seem that some people get up to 30mpg with the 4bt. There is even a couple f250's in the mid 20's range.

A 6bt would be better if you are planning on towing alot. 4bt great for a DD with once and awhile towing. Think of the 4bt as the venerable 300 six just with all its tq coming on at 800rpm to 1800rpm and better fuel economy.

And yes I'm on the search for one. I want I want I want one badly.
85F150 thanks for the reply, great thats good info to know. I want to get around 30 mpg and have decent power. If I can get just a little more power than I have stock I would be happy. Figure the 302 is 200 hp I would like 250 to 300 if possible. Just to add a little more "fun". I don't tow alot so it sound like the 4bt is the way to go. Plus less weight. Thanks for the site I will check it out.

Sorry didn't mean to hijack the thread.

Thats going to be an awesome build
Sorry, haven't been on the 'puter too much lately. Yes, I'm starting out with the M5OD (I call it M5R2) that came in it. They are OK for what I've got in mind, just replace the shift rail plugs so they don't leak and use ATF, no gear lube. I've got a small block ZF S5-42 sitting in the corner that I will eventually stick in after I rebuild it. I would like to find a diesel gearset for it for the Cummins though. From a gear spread standpoint, the M5OD is better for a diesel than the gasser small block ZF, especially since I will be running 3.07 gears. I wanted the 4BT for both the weight and mileage advantage over the 6BT since I won't be doing any towing to speak of, maybe a two sled snowmo trailer occasionally. I decided that instead of painting the frame with epoxy as originally planned I'm going to get it hot dip galvanized which will last basically forever. I'll spray it with some cheap black paint just to color it. I'm in the process of boxing and plating the frame right now before going to the galvanizer. After its done then on to the D44 front and the 9" rear.
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What years was the 4BT available? Was it the second generation diesel for Dodge?
What years was the 4BT available? Was it the second generation diesel for Dodge?
The 4BT is a "breadtruck" engine, there is an entire bb for them at
4BT is a heavy equipment engine.They have been putting them in forklifts and other stuff for many years.Always a good little engine.Excatly like a 6BT but with 2 less cylinders. You can buy a reman from Cummins for around 5000 plus core with turbo and fuel system and the works.
A used one would be nice.
here's where it is right now. I had the frame and all the brackets hot dip galvanized. I also boxed the frame from the front crossmember back to the forward rear spring hangers to stiffen it up. The subframe for the flatbed will be designed to stiffen it from there back. I can finally start putting things back together. Once I get the frame together with Gr 8 frame bolts I will start on the D44 SAS and the 9" rear.


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It's good to see someone every once in a while actually do something cool that they've proposed, instead of "It would be cool to do da-da-da, Im gonna do it someday." Nice work.
Thanks. I've made one change to the plan. I've decided to install the Gear Vendors OD unit that I've had sitting around for awhile on to the 1356 T-case. That will give me 10 forward gears, well, actually 9 because I don't think a GV can be locked in less than 20 mph. If I run 3.73's with 315-75R16's and the ZF-5 small block tranny it will give a real nice gear spread, low cruising RPMs and yet will be much more responsive than the 3.08's and 36's I was originally planning. 5th over (double OD) will give 1560 @ 70 which should be fine for running unloaded. If I'm towing anything I can drop to 5th for 2000 @ 70. Secondary roads would be 4th and 4th over. Should be a ball splitting the gears with the GV, a clutchless, full throttle shift between each manual gear change. :toothless
you can also buy adapters from somewhere like 4wp or your local shop for eye to eye adapters to do away with stud mount shocks:popc1:
you can also buy adapters from somewhere like 4wp or your local shop for eye to eye adapters to do away with stud mount shocks:popc1:
I already have the F250 shock mounts up front which are eye to eye, are you talking about the rears? The stock mount already uses the eye mount shocks in the rear.
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