the posi in my 2000 F150HD is pretty weak. Are theses units rebuildable ?? What type are they, cone ?? clutch packs ??

I may try a fluid change to see if it helps.


Thanks

 

Ford OEM L/S units are "clutch-type". If you are having trouble with noise or vibration, when turning. Be sure to add Ford Genuine friction modifier or Dana part# 43161.

If your truck is an 8.8", you have many options, such as Auburn (pro series is better), Eaton-Posi or OEM Ford (M4204F318).
Dyneer "true-trac", etc.

 

Hello raoul_d, welcome to the boards.

Could you be a little more descriptive about "weak"? What is it about the posi that you dont like? What would you change about it if you could?

 

thanks for the reply and the welcome.

Its not making any noise or anything, it is just weak, when driving up logging roads in the snow or mud, you will get a one-wheel-peel a lot more than I think it should.

It definitely has a factory limited slip, so says the window sticker. If it didn't say so on the sticker I'd swear it was an open diff. If it is a clutch pack then I will definitely try a fluid change and see if that tightens up the action.

It is a F150 7700 gvw with the 7-lug 9.75" axle.

 

When you peel out do both tires spin? If they do its posi, if not its an open dif. Maybe there is just a mistake on the sticker.

 

I know ford sells a rebuild kit for the 8.8, so I'm sure they have to have one for the 9.75 too. Its not all that hard to do, comes with everything you need except a rear end cover gasket (you coudl just use RTV). It also comes with the friction modifier that you need. I still have the factory posi unit in my mustang, but i rebuild it every year. Just make sure not to jam the clutches in there too tight, as I will wear out too fast.

 

raoul_d,

I would look again. I suspect you have the 10.25 inch rear differential. The F-250 LD (97-98) or the F-150 w/7000# (99-02) comes with the 10.25 diff. It is a traction-lok limited slip. This is a strong unit. Are you positive that you have a LS differential. Check the tag on the diff.

Regards

Jean Marc Chartier

 

guys,

thanks for the tips.

I changed the oil this weekend and yes it is a LSD and yes it is a 10.25" diff.

I used conventional 80w90 and left out the additive for now. Haven't been in the snow yet, but with one wheel on wet grass it is definitely tighter. No ratcheting or grabbing on turns, but we'll see when the roads dry up.

 

raoul_d,

You used the wrong oil. Your 10.25 uses SAE 75W-140 High Performance Rear Axle Lubricant F1TZ-19580-B or equivalent meeting Ford specification WSL-M2C192-A. I would recommend changing to the proper weight oil.

Regards

Jean Marc Chartier

 

JMC thanks for the heads up !!!

I just grabbed a 5 gal pail of gear oil in the shop and filled it.

I now have the 75-140.

either way, it seems the two changes have flushed it somewhat and it is a lot better.