My kids truck has the sterling F350 axle in it with a 4.10 limited slip. Traction loc, whatever they called it that year. His axle is out of a 94 just like mine.

Anyway, driving that thing feels weird compared to my two trucks. I can feel the back end pushing me around corners and not slipping like it should. The rear end feels like it's swinging wide if that makes any sense. Just for grins today I jacked it up and tried to break a wheel loose with a 6 foot ratchet I have and it will not move.
That's not good is it? My manual says it should take a minimum of 20 something footpounds to break a wheel loose but nothing about maximum.

I took the cover off and all the clutches are still there and look even on both sides, everything clean and looking good.
Should I tear it down? I've only ever rebuilt one limited slip in a Ford before and it was because it was slipping too much. It was so long ago I can't remember what I did now.

Oh, when he changed the fluid a few months ago he used Mystic gear oil and all I had one was bottle of friction modifier so that's all it got. I usually put two bottles, 8 ounces, in them. That little difference wouldn't cause it to be too tight would it?

 

I personally like mine to lock up heavy like that.

When you turn on dry pavement, you should hear them pop if they are breaking loose.

its pretty rare the stock LS units hook up like that. My thought on that is to leave them be. I'd rather have the clutches keep them locked together.

I'd put more friction modifier in there though.
The modifier, if wasn't in there before, takes a bit of driving to get into the clutches.

 

I personally like mine to lock up heavy like that.

When you turn on dry pavement, you should hear them pop if they are breaking loose.

its pretty rare the stock LS units hook up like that. My thought on that is to leave them be. I'd rather have the clutches keep them locked together.

I'd put more friction modifier in there though.
The modifier, if wasn't in there before, takes a bit of driving to get into the clutches.

 

I'll go get more friction modifier at the dealer tomorrow for it. I need to change the oil in mine real bad too so I'll get enough for both of them. Is that 75w140 synthetic really that good in them? Advance has several brands and not sure which to get. That mystic sucks I think. We've had a couple bearing failures on my equipment here using it.

 

I have used the Mobil 75w140 in my 250 gasser with the ls rear end and it seems to doing fine.Just my $.02.

Red

 

According to ford you need to also remove the hubs to drain the conventional oil as well before putting in synthetic, that is of course fords recomendation, I use conventional still and change mine, the way I see it there is no filter on the diff. and the oil carrys the metal particles and gets recycled through the bearings, unless you haul real heavy that heats the fluid to high temps stay with the conventional, I change mine every 2 years to keep the metal particles out and never had a diff fail.

Companys go to synthetic and say you never have to do routine maintnance on them, they say its oil for life of the diff, thats when I have started to see diffs fail in our fleet. I have found a leaking seal so to pull the axle you have to pull the back plate(half tons) to find the oil is black or milky cause of water and the diffs usually fail sooner or later after that and they have synthetic, I find they are neglectied way to much with the synthetic idea that nothing has to be done with them anymore.

And yes, 2 bottles of friction moddifier for the rear diff on our trucks, I've been only running 1 bottle since summer to get my clutches to grab a little more. Your sons truck may have been shimmed tighter if the LSD was rebuilt once before.

 

I just installed a Ford Limited Slip in my 4.0 Ranger. I put "Red Line" 75w250: (Racing oil) in it. It already has the friction modifier in the oil. I called Red Line to confirm this before purchase. So far no problems.

Rog

 

Yea, but we are not as rich as you Rog.

 

You never add more shims than are already there.
If somebody did that, thats a No NO.

if you got .5 worth of shims, you add back in .5, not .51, or .49, .5 only.

 

Really?
William: Add the cost for approx. 3 Qts of Synthetic oil PLUS the friction modifier and it comes out about the same.
Rog

 

Where'd ya hear that?

 

I put Lucas gear oil in mine. Good stuff, not too expensive, and already has friction modifier in it IIRC.

 

I'm pretty certain noone ever rebuilt my sons before. They just swapped the whole thing from an F350 to his F250. I'm still trying to figure out what happened to mine. It's the original rear end housing but it's got a detroit locker in it. I love that thing. I think it's original but I didn't even know they had them in 94.

I have also run into a LOT of failed rear ends before because of synthetic oil and people that mostly just drive in the city and never get them warm. Explorers with the aluminum rear end are real bad. So are the mid 90's half ton 4x4 chevys and Fords with 4.10 ratios. I rebuilt way too many of all of them. I can't remember ever having to get into a 1 ton before though. I guess that's a good sign.

I do pull a lot and pull heavy. My kid does too so we better get the synthetic. I change mine about every year normally. I might need to start doing the front oil and wheel bearings twice a year though. New seals, new hubs and everything and I somehow got water in the hubs. It's been swimming a few times recently on the farm. I still can't see how the water got past those new warn hub seals. It kinda looked like it went in where the screws are so I put a dab of silicone on each one now.

 

Just what I've read. =(

 

From the mud bog guys here.

If you drive your mud rig to an event, the axle will be hot.
When you put it under water, the cool or cold water causes the axle to drop in temp fast, which pulls water in through the seals and breather.
You may or may not make it home.

If you trailer your rig to the event, the axles are cold when you hit the water, no problems with drawing water in.

So if they drive to the event, they get there very early so they can park long enough for the axles to get cold before hitting the mud.