4BT Cummins 4L85 Long to Short

[bowfaber]

I'll give the dessert first! 1968, 4BT Cummins, 4L85e transmission, Long box cut down to a short box, used a short box frame. Rear air bags for hauling, AC, Hydro boost and 4 wheel disc brakes, quick ratio power steering, the list goes on. I have put 2,700 miles on it so far, no issues. Currently getting anywhere between 18-23 MPG. It's not afraid to work either...

[bowfaber]

Long story short, I found an original short box patina truck in New Mexico. Part of the deal came with an original short box frame. Went down and drug them back to Iowa. Started the build and found this truck 7 miles from home. Bought it and used the short box frame from NM.

[bowfaber]

frame work

[bowfaber]

Why buy when you can build!? C notch, 1/4" plate, Universal bump stop from Speedway. Sand blast, primer, undercoat, and paint suspension parts

[bowfaber]

Front end came out of a 71 GMC 1/2 ton giving me front disc brakes. McGaughys drop spindles up front, 4 inch CPP drop springs in the rear. New 3.08 Eaton Limited slip.

[bowfaber]

Weld on disc brake kit from Speedway. First, the axle must be turned down to allow the rotor hat to slide over it. Next, the inner circle of the hat must have material removed to slide over the axle.

[jdoisher]

Awesome!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Build!!

[dragn91]

Very cool build but it's in the wrong section this is the 60-66 but non the less I enjoyed seeing the build I'd love to find a 4bt for my 66

[rickoner]

Great build and documentation!!! Worth reading a couple times.

[Jeff La]

Great job and thanks for documenting. Hoping to do a 4BT one day.

[dieseldude4bt]

Looks great! love it.

[Dieselwrencher]

Great fab work, nice welding, and awesome truck! Would you like it moved to the 67-72 area?

[bowfaber]

yes please!

[hick]

I just realized that I will never amount to any thing in life after looking threw this... Cause this is my dream build.

Its disappointing to hear about your mileage. I would have expected more.

Does the insulation help quite a bit? I enojy the knock of a cummins as much as the next guy, but I enjoy a stereo that doesnt need to be cranked all the time as well

[bowfaber]

I was extremely disappointed with the mileage. I was hoping for nothing less than 25 mpg. The first few tanks was 18-19 mpg. I trimmed the shift points, lowered the TC lock up, and didn't drive it like I was 16 and got 23.4 mpg. I built it to be a nice driver with good mileage. It has good road manners but wish it was north of 25 mpg. I will put a taller tire on the rear and let you know what happens.
Without all of the dynamat I couldn't drive it without earplugs. Drove with Ma'Lady on it's maiden voyage to a drive in movie. We both wanted to throw up after the trip because of the noise and vibration. That's not a problem now. My main problem now is the wind noise coming through the windows and doors. I hear some engine noise but it's fine. I hear the turbo whistle a lot more.

[sodly]

Just curious.... what did you do with your original wheels/tires?

[bowfaber]

Originally Posted by sodly

Just curious.... what did you do with your original wheels/tires?

Still holding up the long frame.
Posted via Mobile Device

[bowfaber]

Originally Posted by bowfaber

Still holding up the long frame.
Posted via Mobile Device

Posted via Mobile Device

[BigBlockBurris]

AWESOME build, and thank you for sharing!

Two questions.
1-Where did you get your motor mount rubbers? I know you fabricated the metal part, but what about the rubber isolators?

2-What exhaust is that?

Thanks!

BBB

[bowfaber]

Rubber isolators came from the step van. They were the factory mounts. I did some research on this topic and found these isolators were one of the best ones to use because they dampen the vibration good, and I already had them- bonus!
Intercooler tubing came from Frozen Boost. I went to JEGS and got some 3 inch stainless 90, 45, 30, 180 bend (Tip- buy 180s, you can cut them in half to give you two 90s for less money.) Started cutting and fitting the pieces until it was how I wanted it. Welded them up and ground off the welds to make it appear seamless. 4 1/2 inch wire wheel finish. The turbo down pipe required a tight radius 90 which I got off Amazon. I cut the v band off the factory down pipe and welded it to my new stainless piece.

[68Gold/white]

Look'n Good!!!

[bowfaber]

truck

[deejaaa1]

i'm only on page 2 but want to respond before i lose my thought.
your fab skills are top notch. love the redneck dent puller.
have you used the Tite seal over any long periods? does it hold up to weather? i've used some in the past but it seemed to be no more than a rubberized spray that washed off when it rained.

[deejaaa1]

Originally Posted by deejaaa1

i'm only on page 2 but want to respond before i lose my thought.
your fab skills are top notch. love the redneck dent puller.
have you used the Tite seal over any long periods? does it hold up to weather? i've used some in the past but it seemed to be no more than a rubberized spray that washed off when it rained.

edit: finished the thread. awesome build. GLWS.

[bowfaber]

The Titeseal works great in the cab, and good under the truck. It seems to hold up better when it's painted. If it sees a lot of sunlight it gets weak and will come off easy. I drive a lot of gravel roads so it gets some good abuse. One place on the rear cab support gets a lot of rocks thrown at it and the product is gone. My next build I will try a rhino bed liner on the underside, if it's visible under the hood (like my firewall) it will have Titeseal with paint. I like how it lays down, looks better painted, and it's not too rough looking.