I want to thank everyone for their help. Its been great. I've got this thing going pretty good. Long way to go but I'm off to a good start.

I wonder if anyone can help with a way to determine if I've got a posi in my 68 f-100, 360, 3 speed?

I did some basic engine stuff with a new ignition and took it out afterwards to see how it was running. I did a few burn outs and got 2 hot tire lines every time. Unless I'm way off base,thats posi. Is there a number of the rear end of some other way to i.d. the differential? I'm going to drain and flush it soon and I'd like to know if I need to add posi oil like I do in my vette.

 

Jackup one rear wheel and see if you can drive off the jack. Most likely the wheel off the ground will spin.

If you have both wheels off when you turn one they should rotate the same direction. If one goes forward and the other backwards you do not.

There should be a metal tag connected to the rear end. It will have gear ratio and other info. As to oil it's agood idea to change them every 30-60k mi depending opon service. If it's a limited slip, more often and may need to an additive depending opon the oil. With out it will make noise every time you turn.

 

br, If you are making two marks you have a Limited Slip rear, posi is a GM thang.

An open rear will not make but one.

To find out if you have a factory installed LS rear look at the door tag, it will have a letter before the number like B9. B9 = 3.55 Limited Slip.

hope this helps

John

 

some times if an open diff is about shot it can lock together and act like a posi. look and see if its still got a tag on the diff if its a limited slip itll have an L in the ratio numbers like 3L50

 

There may be a separate tag on the rear end with just an L on it.

As original, the rear end tag is at 5 o'clock as you're looking at the carrier, the L tag will be at 4 o'clock.

Not all Limited slip rear axles are 9 inchers. From 1959 thru 1964, if Limited Slip is present, the rear end will prolly be a Dana 44. 1965/68, it could be either way.

Don't be surprised if a Dana 60 is present either. This Dana 60 (actually a 60.2) was optional from 1961 thru 1968. The bolt pattern is the standard F100: 5 x 5.50.

What rear end is it?

Look on the Warranty Plate, located on the left door face near the latch. On the second line at the far right is the AXLE code.

 

Thanks ND, I found the door tag, I also did a little surfing around the site and theres no question that you know Ford codes better than just about anyone. From what I get I think, if I have a limited slip, it was put in later. I would appreciate your giving me a rundown on the codes though:

VIN: F10YKD27365

131 J F100 5 81 C 17

05000 172 3800 55

Thanks, BR13

 

F10 = F100 2WD

Y = 360 2V

K = Kansas City Assembly Plant

D27365 = 1968

131 = 131" Wheelbase

J = Rangoon Red

F100 = F100 2WD / 5,000 lbs. GVWR

581: 5 = Red Crush Vinyl & Red Bar Pattern Vinyl / 81 = 81A Standard Cab

C = Ford 3 Speed Manual type 3.03 all Syncro.

17 = Ford 9 Inch / 3.25-1 / Non Limited Slip / 3,300 lb. Rear Axle Capacity

05000 = 5,000 lbs. GVWR

172 HP @ 3800 RPM

55 = St. Louis, Missouri Ford District Sales Zone (where original selling dealer ordered the truck from)


A Limited Slip kit could be purchased over the parts counter, if the customer wanted to add it: B9AZ-4800-C (fit: 1959/68 and early 1969 Ford cars and F100's with a 9 inch rear axle.).

 

see... The word POSI does not relate to Fords.

 

This chart only has a fraction of the 9 inch rear axle codes offered from 1957 thru 1987.
There are dozens more...and that's just for F100/150's, Bronco's and Econolines.

#17 = 9 Inch Axle Code = 1965/77 = 3.25-1 / 3,300 lb. Rear Axle Capacity

#15= 9 Inch Axle Code = 1975/79 - 3.25-1 / 3,750 lb. Rear Axle Capacity

Cars use a different code.

First year Ford offered Limited Slip = 1959.

Posi-Traction is generally known as a GM term, but it wasn't always.

First American car that offered a Posi-Traction Rear Axle = 1956 Packard.

 

I noticed this after trying to figure out if I have limited slip and I doubt I do but I was wondering if you could tell me about my f100 based on the vin. Its F10GNV62715. I have always wanted to know more about the truck itself but with work at the shop its hard to have the time

 

The VIN won't tell you what the rear end ratio is but the warranty tag on the back edge of the door will. --this assumes that the original drivers door is still on the truck, the tag is still affixed to the door and that no one has changed or altered the 3rd member in the rear end.

 

F10 = F100 2WD pickup.

G = 302 2V

N = Norfolk VA Assembly Plant.

V62715 = 1975.

Please ask future questions in the 1973/79 F100 and larger truck forum, this forum is for 1967/72's.