on my 95 150, is there anyway to tell... without dropping the pig on the front, if I have a posi or not?

I am familiar with ford diffs, but not dana diffs. I was wondering if there would be a spring around the pin like there is on the rear of my 8.8

and I was also told you can only put certain gears on the carrier, so I am kinda perplexed.

Any help would be greatly appreciated

Thanks

Chris

 

i would spin em. im not sure how to tell on posi if its the same as limited slip. On my limited slip on my car if you have both wheels in the air and turn one,the other will spin the other way, if you start changes directions fast they will both spin the same way.

wish i could be more help

matt

 

Jack up the front end. Leave the case in 2h, lock the hubs. Spin one wheel. If the other wheel spins the same direction, it's limited slip (posi is a GM trademark). Opposite directions, open differential.

 

Here is another way:

Put the truck in 4L. Put the trans in park (low gear if standard). Lock the hubs. The idea is to lock the wheels to the axles, and to lock the driveshafts.

Jack up ONE wheel. The other should stay on the ground. Attempt to spin the raised wheel with a lug wrench, your hand, a torque wrench, etc. If the vehicle has a working limited slip, it should take at least 20 ft. lbs of torque to spin the one wheel against the resistance of the limited slip clutches. If the truck has an open differential, the one raised wheel will spin easily. If the truck has limited slip, but the clutches are shot, the wheel will spin with some resistance, but not 20 ft lbs.

Both GM and Ford recommend this method for testing the efficacy of factory limited slip setups.

I would point out that it is quite unusual to see limited slip in a FRONT axle, especially from the factory, due to the significant negative effects on handling and steering feel.

 

fefarms,

99.9999% of the time, you know what you're talking about. In this case, I have to disagree. If you lock the hubs, lock the drivetrain (either in park or in 4L/1st gear, as you described), and jack up only one wheel, it will not move regardless of whether a vehicle has a limited slip differential. It will only move if something is seriously broken.

 

it shouldnt turn if everything is locked in gear and 4 low i guess he means its 20ftlbs to make the clutches slip? if they are frozen you would not get them to spin. if they were frozen you would have one heck of a time going around turns as well. if it were the rear you would hear your tire chirp. I could be way off on this but in my mind if you had an open diff i would think the one in the air could spin freely. andy why is this wrong? im just trying to understand.

matt

 

Ok, let's assume it's an open diff, for purposes of this discussion.

Think about it in reverse - if you have one wheel up in the air, and you start the engine and put it in gear, the wheel will spin like mad. This proves that the wheel is connected to the engine (duh). So if you kill the engine, put it low range or park, the wheel won't move because it's 'locked' to the engine.

I guess you could get the wheel to spin - but you have to exert enough torque on the wheel to get the motor to turn over. Going through that much reduction (on a manual) or going through the splines on the tranny requires more torque than I can muster.

 

now it makes sense, thanks andy

 

I blew it. What was I thinking?

Don't lock the driveshaft. Leave the truck in neutral. Spin the one raised tire.
If an open diff, the one tire and the ring/pinion and driveshaft will spin with only the slight mechanical drag of the gears. If a limited slip diff, you will have to overcome the resistance of the clutches in the differential carrier, against the stopped tire/axle.

 

I was told by someone at Dana once that they NEVER made a limited slip front diff from the factory and that it would have bad road mannors. Of course, just because the guy answers there tech line, it dosen't mean he has all correct info.

 

If the truck had the factory limited slip--the driver's door jam sticker will have a "2" in rear of the rear differential code--for example:code H92 would mean that the truck has a 3.55 limited slip in the rear axle (H9)and a limited slip in the front (2). This code would appear under "axle" of this sticker.

The factory front axle limited slip was a 252 dollar option on the 92 F150 4x4.Ford was the only manufacturer of the Big Three that offered factory front limited slip in a pickup.

There is also a factory sticker that is upside down on the passenger front axle and facing towards the rear. It will have the differential ratio and will also state "standard" if the differential is open. Look for the sticker from underneath the passenger door--I looked for this sticker when I was hunting for a truck--it is an easy way to determine what the differential ratio is for the truck--without getting the salesman to get the keys to the truck.

 

moved to appropriate forum.