details!

Posted by 26Red on October 04, 2005 at 08:00:17 from (170.92.100.2):

In Reply to: conversion photos! posted by 26Red on October 04, 2005 at 07:47:48:

This was reposted from another site:
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"As I reported a few weeks ago, the long time coming Dodge Cummins Dakota
project is on the road. I now have some pics loaded up on the web, sorry no
thumbnails or anything fancy. There are 4 as follows:

www.execpc.com/~jemery/Pics/cumm1.jpg
www.execpc.com/~jemery/Pics/cumm2a.jpg
www.execpc.com/~jemery/Pics/cumm4a.jpg
www.execpc.com/~jemery/Pics/cumm5a.jpg

The only thing missing is the hood and the A/C hoses.

Just a little background. We bought the truck new in 91 for a business
truck. Within a week after buying it I had the rear springs out and had
another leaf added. Seems to be a common problem, I had to do the same thing
to my Toyota in 82, they must spring these things for people that don’t ever
haul anything. The electronic ignition died the first year. Then about
three years ago the rear axle started making all kinds of strange noises.
The garage that my partner takes it to (I was not driving the truck at this
time) said that the axle was falling apart and that they could not fix it, go
to the dealer. Screw that, having done many Dana’s from 23’s to 70’s, I took
the thing apart and reset the carrier bearing adjusters as they had loosened
up.

About 2 years ago or less I was roaming around a heavy/medium truck yard and
saw a pile of 4BT Cummins engines with THM-400 trannys attached. A friend of
mine who is well seasoned in Diesel conversions looked at me and said "you
know", and I said "yea" (must have been Diesel telepathy). At that time the
Dakota was approaching 150k miles and the mileage was a pathetic 16 and I was
now driving it whilst the partner got a new vehicle. The guy at the yard
gave me the keys to a potato chip truck and told me to take it for a drive,
which we did. This particular truck had 70k miles on it. I gave him around
$2k and he pulled the pack out of the truck and junked the rest for the
aluminum, that’s where all the other 4Bt’s were coming from, potato chip
delivery trucks. I got the engine/tranny and all the parts I wanted related
to that such as shifter, drive shaft, air cleaner, etc.

We got the thing back to the shop and started working on mounts for A/C and
vacuum pump and moved the alternator and such. Also decided to add a Morse
cable tranny modulator as they came with a fixed one, it shifted at X rpm no
matter what. The engine used an 8 groove serpentine belt and so I added an 8
groove small GM alternator (105A) and a 10 groove Sanden A/C compressor and a
flat pulley (running off the back side of the belt) Ford vacuum pump. I
wanted the alternator and A/C up high and I wanted the A/C where the
alternator was for plumbing reasons so the alternator had to go on the other
side and due to hood height problems it had to be on the small side. The
alternator on my suburban became a sample and it fit OK, so just got another
of the same thing. I also machined the grooves off the fan idler (the thing
that one might think is a water pump but it’s not) so as to drive it
backwards. Had to do some major rework of the intake manifold cover plate
and the tube connecting the turbo’s compressor discharge to the intake cover
for hood clearance reasons. Also added a flame primer from a Perkins Diesel,
all of $20, rather than pay $600 plus for the Cummins electric heater unit.
The first test run of the new belt/pulley system broke the alternator case
and prior to that the belt kept running off the crank pulley to the inside.
Added another brace for the alternator and the pulley problem was caused by
Cummins not having a skirt on the back side of the crank pulley, so I made a
new one with a skirt. Second test run (on a skid) was perfect.

While this was going on the rear axle fell apart again. I had picked up a
Ford 9" from a Bronco to re-work for the Dakota primarily because I needed
the 2.5 gear ratio to run the supplied THM-400 with no overdrive, and it also
was a much stronger axle that that 7-1/4" thing. Which in my opinion is the
correct way to design a truck, pick the axle ratio for your 1:1 high gear,
screw the overdrive, they are nothing buy marketing gimmicks. Anyway, I
decided to put the Ford axle under the truck with 3.5 gears while still
running the V6 which turned out to be a smart move, that was one less
"project" to figure out later. Switching the gears back to 2.5 later was a
breeze. Also the 11" brakes on the Bronco axle are MUCH better matched to the
Dakota’s front disks, my braking effort increased dramatically and yet I
still cannot lock up front or back easily on their own. I also put in a
"True-Trac" which I just love.

So then about 2 months ago it was just one of those days, the engine/tranny
had been sitting on a skid for 6 months or more and the position of the moon
and the phase of Jupiter, I had some people over at the shop and we just,
with little discussion, decided that this was that day and we pulled out the
V6 now with 202k miles on it and stuck the 4BT in there and began the long
installation process. I added a new cross member (removable) ahead of the
main one under the engine. The front engine mounts sit flat on that new
cross member. The Cummins engineering book makes a big deal about not
mounting a 4 cylinder Diesel to rigidly. So I did some tests on some
different mounts and it turns out that the mounts from the original V-6 were
soft enough and so I used them. The motor does vibrate a bit at idle but I
can imagine it would shake the truck worse if the mounts were stiffer. Then
came the oil pan. I ended up using the flange and the first 1-1/2 inches of
the pan, the rest was fabricated from scratch to fit the space exactly. I
decided to do this with the pan rather than touch the cross member which the
front suspension and the steering rack were all tied to. Ended up going wide
and deep to maintain the 3 gallon capacity, also ran tubes through the pan in
5 places and used long studs so the pan is actually held from underneath. I
figured with the idle vibration and the added weight of my additions I’d
rather have it held from below that to hang totally from the flange. Also due
to tight clearances between the front of the pan sump and the cross member I
added a strut from the back of the tranny going back to the center bearing
cross member to keep the entire assembly from moving forward during braking.

Other little items were mounting the Morse floor shifter in the old hole left
by the 5 speed and gutting the wiring leaving only what I needed. Radiator
is from a V8 of the same year. In the pictures the A/C hoses are not
installed yet, it seems that Parker is having delivery problems and I just
this week got the fittings I had been waiting 6+ weeks for.

As I reported earlier I am now consistently getting 26 mpg around town. So
far I’ve put 2k miles on but I have not yet tried a long highway run nor have
I tried towing anything yet.

Only remaining issue now that A/C hoses are on is getting the front to sit at
the right height. It dropped 1-1/2" and an alleged 2" lift kit from Rough
Country raised it 4-1/2", so need to remove the spacer and cut in half, that
should put me right were I want to be."
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Wish I had the shop space and time to do this conversion! More info is on the TDR website.

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