I posted this in the 80-96 section but thought I might miss someone who may not look at that section who may have the answer. A while back I posted all my codes for the rear axle and everyone replied that it was 355 and open, which was fine with me until today. I happened to go up a gravel road which I don't normally do and for some reason I looked back and the way the gravel was turned it struck me as odd.(don't ask why) So I decided to back this thing back into the main paved road to do some research. Upon the first time I reved let off the clutch I didn't rev above 2000 cause I am not interested in replacing the clutch right now but upon my looking back at the road I noticed I had two black marks about 3 foot long. I thought open meant you only had traction on one tire?? So I did it again reved let off and heard a pop looked back and seen one mark. What? So I did it again to make sure the first time was not a fluke. I partially let off the clutch as if to engage the rear then so I pushed it back down quickly reved and let off there were two marks. Now I am lost. The pop wasn't anything serious cause I drove it a good distance without anything out of the ordinary happening (could have been a rock). This sounds like limited slip to me but maybe I am wrong and sure would like someone to explain. Thank you for your time

 

I'll give your question a go, but by no means am I an expert.

Here's a link for you: [link:www.ring-pinion.com/tech.html|Randy's Ring and Pinion Service]
This explains a lot about differentials in general. There is an article towards the bottom of the page labeled "Myths Regarding Diffs." At the bottom of that article it tells you that posi and limited slip is basically the same thing. I take that to mean both axles are locked when a large load is placed on the diff, such as a high torque requirement (burnout), but not necessarily tightly locked all the time for wear reasons similar to an "open" diff. Hence it "slips" when not under load.

A true locking diff is evident when attempting to turn a corner. The vehicle will "buck." Air lockers are those that require a pnuematic pressure to hold the axles in a "locked" up position. I believe they act as a limited slip if they are disengaged.

The open rear end is one that requires a certain cetrifigal force to enguage both axles. So as you slow to take a corner, the "trailing" axle disengages, thus saving on wear and tear in the diff.

The only way to know for certain is to check the build tag on the diff and reference it. It's sounds like you have a limited slip, though. If any of this info is wrong, I hope someone wiser corrects my thinking.

Kerry
"Ran fine for me, must be the operator..." -Dad
'82 F-150 4X4;
300-6; MSD Blaster 2 Coil;
245,000 original miles and still rolling

 

Thanks for the feedback.

 

Like I said, I could be wrong.

I have been investigating my own rear end. The Ford 9" isn't completely bullet proof, as I have found out. Just sharing what I've found.

Kerry
"Ran fine for me, must be the operator..." -Dad
'82 F-150 4X4;
300-6; MSD Blaster 2 Coil;
245,000 original miles and still rolling

 

jack the rear end up with the truck in gear,turn the tires, if they spin opposite directions, you have an open diff, if you cant spin em, take it out of gear, now try to spin em, if the spin the same direction you have some kind of a limited slip

1985 F-150/351Ho/c6/4wd~94,000 miles
1979 F-150extcab4x4/460/c6/6inchlift w/60rear44frnt (250 axles and springs)
37 inch boggers