Fuel Economy- A Funny Thing Happened

[fox]

I have an old bread truck with a 4BT and 4 speed manual 465- with 3. 73 gears. It runs down the road with 11,000 lbs every day. pushing a lot of wind too!

It gets 14 MPG, it is against the governor most of the time. Runs about 60-65 with 215-85/16 tires.

The 4 bt will get it done. It isn't the most fun to drive but is economical.

 

[Scot]

Todays question is: Who knows the best way to add cruise control to the 4BT 73 Ford manual trans?

Cruise was an option in those trucks atleast back to '75.



I used a combination of parts from a '78 and an '84. Prior to '80. the servo mounted on the engine and used a toilet bowl chain looking thing to pull the throttle. '80+ used a fender mount servo with a sheathed cable which will clip over my Lokar throttle.



The amplifiers appear the same and will interchange. The 80+ have the resume feature.



Cruise cancel is achieved by a second (redundant) switch and a special brake booster <80. After 80 they used a vacuum plunger instead of one of the switches.



There are atleast 3 amplifier to column harnesses. It plugs in between the harness to column and column. <78, 78-9, 80+. 78-9 did not have a horn relay. All orhers did.



There are atleast 2 amplifier to servo harnesses. <80, 80+ based on the servo end plug.



Hope that is all clear as mud...



So what I did was to use a 78-9 amp to column harness, 84 amp, amp to servo harness, servo and vacuum switch.



The vacuum switch is looks a lot like the brake switch and is mounted right beside it on a simple bracket.



I initially tried the 84 amp to column harness. All column features except the horn worked properly. It now honked with one of the cruise switches.



My guess is that the pins could be moved around to make any of them interchange if you poured over the wiring diagrams.



Fordtrucks.com has some info regarding moving pins so that a 78-9 column will work in <78 trucks.



I used a late 80's pickup wheel that looks like a 90's Explorer wheel because it is so hard to find the earlier factory cruise horn pad intact.



I used speed signal off of my electronic speedo but you can also use the OEM inline one.

 

[DKarvwnaris]

I've seen first hand the mileage benefits of a 4bt against a 6bt. For a 1/2 or 3/4 ton pickup with moderate towing, there is nothing else I'd want to use. My 5. 9 is a stump pulling mule, but the reality is, I don't need all the power it has for driving around town most of the time.

I'm trying to get the time to get back to my 4bt repower this winter, but everything else is sucking up my free time.



Something I think needs to be thought of in regards to lower mileage in the newer model trucks beside higher HP ratings is the lower BTU's in a gallon of diesel fuel today as compared to just 10 years ago. The refining regs of fuel are pushing the sulfur out to reduce its emissions levels, that can account for some of the MPG losses that most old school ram diesel owners see compared to the newer bodied goats. I've never had the option to consider fuel mileage an issue, my weights are too high to even try to get by with a soft foot when I'm hauling my equipment around. For power and comfort towing, I fire off our class 8 converted motorhome/toter, which amazing gets 7- 8 mpg loaded and 9. 5 bobtail if I set the cruise at 65 and stay on the flats.



My old Jeep was getting in excess of 25mpg with the 4bt and a 5 speed transmission in it. 35" tires for lower RPM's didn't hurt either.