86 6.9 rear end/suspension questions
 

Hello everyone I hope all is well with you and yours. Just bought a 86 xlt 250 6.9 IDI/4speed in Arizona with 103k orig miles and little rust for 1700$!! Excited about the truck being that it's my first one, I'm 24 yrs old and I want to do right by it and make it last. Primarily a Mopar guy, but couldn't pass up this deal. Please pass some knowledge my way, honestly any thing helps.

My questions are:
-my truck doesn't have a front axle, how do I level the truck out to how high the back sits for cheap while being reliable? (Would like to put slightly taller tires for mileage, currently 265-75-16) so I also need spacers to keep the turning radius right?
-instead of ripping the diff apart, what vehicle in the junk yard will have the same rear end width and have 373 gears??
-how do I install a tach on a mechanical diesel?
-what general problems or issues should I be looking for?
-what mods can I do for a little extra power while retaining liability? Currently stock exhaust which I would like to change, should I go straight 4 with a down pipe or 3 or what?
-after installing the tach, what rpms should I shift at and what is the redline?

Thank you in advance for sharing some info!

Moving to Texas from so cal in a month so I need her to last!

Welcome to FTE.

Nice snag ...

I am also a Mopar guy, and only those that know me personally knows the pun in that!

These trucks have a TIB or TTB front end depending on 2wd or 4wd ... Lowering or lifting is not done easily, though very possible.
TIB = Twin I Beam
TTB = Twin Traction Beam

You won't find 3.73's ... These trucks delivered with either 4.10's or 3.55's and you would have to either look on the axle tag or door axle code.
Axles that will fit are 80-97 F250/350.

As for Tach, You have to either go factory or use a programmable addon that uses a VRS type pickup (Variable Reluctance Sensor), Commonly called a Diesel Tach. There is a location on the IP gear cover for a Tach sensor (right by where you add oil).
I highly recommend waiting until you get to Texas for this, Texas has a lot of salvage yards and you likely can dig up a factory cluster and sensor.

Most general problems are

• Glow Plugs, Ensure they are Motorcraft/Beru ZD1A ONLY!
• Glow Plug Controller - This old school type controller fails ON ... Smart folks convert to the newer system, others bypass with a button.
• Fuel Filter head Heater and Fuel Return Cap leaks causing Air Intrusion thus difficult starts ... If it starts then dies, then is hard to restart, you have Air Intrusion.

Power Mods ... Add a Turbo, Diesels like Air, Lots of it!

Redline is 3300 RPM, Shift point is where it's needed, usually lower than most think, especially those that come from a gasser world.
Diesels are low RPM high Torque motors the opposite of most Gassers.

You should be able to find lots of good parts for these old girls in Texas ...

-Enjoy
fh : )_~

Festus I really appreciate your post! Very informative!

Hi .. welcome . .. i'm also a mopar car and ford truck guy

I think the obs trucks had 3.73 but the bullnose only had 3.55 or 4.10's commonly
But my link to the ford index seems broken .. but somewhere i have the axle code screenshot

Should be okay with tires up to 35 inch but if you change ride height you must account for changes at all the pivot points not just one .. but you might get some small adjustment with a few cut leafs sectioned an welded and a variable degree bushing but don't get too far without other bigger modification..

I got an isspro tach .. i like it .. runs off 2 magnets on the motor balancer .. here's a link .. al so can look page1 for common maitanance issues and things to watch for ..

https://www.ford-trucks.com/forums/1...ed-lock-4.html

Congrats on the truck. . I think you'll like it

Ohh shifting. .. around 1300 gets best milage .. when i'm not in a hurry i shift around 2k and keep it around there