This just started yesterday. While driving down the freeway I was challenged by an '08 Charger Hemi while driving my '86. After I dusted the guy I shut 'er down at 115mph. Then a ways down the rd the OD shut off and I was back in 4th. I put it back in OD and it was fine for a bit then it shut of again on it's own. So this morning on the freeway again it wouldn't go into OD again for about 5 miles then was fine and it keeps doing this....HELP!! Whats wrong with my OD???

 

As it appears to be a intermittent problem check wiring to O/d first
Connector plug on O/d relay has known problems with age.

 

Its not that...Ive installed a different switch

 

You probably ruined it by street racing . Which,, BTW, is a way to get your thread locked or removed. It's against the CF rules.

But check the wiring connections. It's possible that the relay is bad or that either the pressure switch or solenoid inside the OD unit may be going out. When was the last time you changed the fluid and filter??

 

I've had the car for about a year and a half and Ive never changed the fluid or filter.

 

Switch only triggers the ECM which controls the O/d relay.Need to check that you have 12V at terminal on O/d.

Lack of correct attention to O/d service is major cause of O/d problems, that is why they have a bad name because people treated them as like a regular auto that can go 50K without a fluid change

 

It's always a good idea to change the fluid in the OD every 12-15K miles. For most people, that's once a year, maybe every other year depending on how you use the car.

It's a simple job to do and I would bet that its been a long time since it was done. Wouldn't hurt to change the gear oil in the 4-speed portion too. A good 80W-90 GL5 gear oil works fine.

The OD unit uses the same filter that is used in Ford FMX auto trannys (late 60's through early 70's Torinio's, Cougars, even some F-150's). Here's some common parts store numbers for the filter:
CarQuest - 85926
AC Delco - TF184
FRAM - FT1024
NAPA - ATP14717
Ford - D0AZ-7A098-A
These filters will run around $7 to $9.

A fluid change takes about 2 quarts of Dexron II or III ATF (don't use synthetics!). You will also need some good RTV sealant for the pan. Somehting like "The Right Stuff" or get a tube of MoPar RTV sealant from a local Dodge/Chrysler dealer. Don't bother with the paper or cork gasket that comes in the overpriced kits from the mail-order catalogs).

The cooler lines hold about a pint of ATF. You can use low pressure compressed air to blow out the lines or get a can of flush made for that job.

The filter has a rubber grommet that holds it in place. You will need to re-use it as most filter kits do not come with one.

When you remove the pan, make sure the rails and the OD case flange are very clean and the pan rails are straight. Be careful tightening the small bolts. They need to be tightened evenly but not real tight.

If you blow out the cooler lines, raise one rear wheel and spin it for about two minutes. This will fill the lines; top off the OD unit and you're done.