It seems that my rear axle (3.55 LSD) is making a bit of a fuss when I turn tight. Such as in a parking lot or moving a trailer around in tight quarters. I can't hear it, but I can feel it. Feels abrasive.

I recently changed my rear end oil when I put in the Mag-Hytec diff cover. I used Amsoil, but I can't recall the weight right now. It was what was reccomended.

My question is: Did I need to use an LSD additive (friction modifier), even though the Amsoil bottle said I didn't need to use anything else?

I'm not positive the LSD is the issue, but it's the first thing I'd suspect.


Thanks,
Chad

 

My truck kicks around every little turn too. I havent changed the diff oil yet but with 220K plus its probably worn out. I dont mind it much until it rains and the roads are slick. I wouldnt think amsoil would need the modifier but I dont know.

 

Amsoil severe gear fixed my work truck, it was the heavy visc. 140wt

 

Try adding friction modifier half a bottle at a time till it's like you want it.
I don't see how any lube manufacturer can claim you don't need modifier with their products. Every differential is different as far as wear on the clutch packs. Some will take more additive.
Too much additive though and you loose your anti-slip.

 

Soooo, what you're thinking is that my LSD is trying to stay "hooked up" almost like a spool? That makes sense I guess. I've got tons of experience with real lockers and spools, but none when it comes to LSD's. This is the first one I've had. I just assumed that Amsoil knew what they were talking about. I also assumed that the friction modifier additives would increase the amount of clutch action. Apparently I got that backwards!?!

I'll pick up a tube of additive tomorrow when the stores open back up. Any brand I should look for? Or avoid?

Also, is it probable that I've damaged my diff by running without it? I hope noe, because I don't want to try to fight with Amsoil about it.


Thanks,
Chad

 

Yeah you did.
Friction modifier looks like a tadpole under the microscope. The way it works is the 'head' part of the additive embeds itself in the clutch face, the more force applied to the clutch when the wheels slip pulls the additive out by it's tail and causes the clutch to grab more.
I never paid much attention to additive brands, just bought what they had on the shelf at Napa. Seems to work fine.

 

Right on. Thanks sir. I'll get some tomorrow and throw it in before I go to play in the snow.

What's the verdict on clutch damage? If it's getting grippy, am I risking early damage?

 

If it has 200k or more on it I would tear it down and put new clutches in it.
Actually, any rear end needs cheched unless super low miles.
You can tell the shape of the clutches normally by just lookin at the oil closely that you remove from the rearend.
You don't want the clutches wearing enough that you shell the spider gears.
Been there done that.
Mine at 215k were worn so bad most of the clutches and steels were nothing but the alignment ears.
BUT I have no idea what was in the rearend, if they were running pure GO when I got it it would wear them out alot quicker.
After I rebuilt mine it grabbed badly with just one bottle of friction modifier.
I ended up with 2 in it. These were 8oz if I remember right.

BTI

 

I figure on pouring in 4-6 ounces at first and running it for a tank of fuel. See if it gets better. If it doesn't, I'll double it up.
Mine has right at 100,000 miles on it, and only about 5,000 on the oil that's in it right now. I don't know exactly what was in it prior to my ownership, but the diff cover had been removed at some time. Definitely not a factory RTV job when it was put back together.
I only took it apart to change to Amsoil and install the Mag-Hytec cover. It was not acting strange at all. Everything was just fine. Oil looked good, no major chunks of stuff on the magnet or anything. I cleaned everything out reall good with solvent and let it dry before I reassembled. It took a long time before it started to act up. About 5,000 miles before I noticed anything.

I'll let you know if it gets fixed! I really hate doing gears on Dana axles. I like the removable third members of a Toyota or 9 inch much better. I guess 14 bolts aren't too bad with the drop out pinion.

Hopefully it'll be OK.

 

I was under the impression that friction modifier actually makes the clutches slip more.
This makes sense because if you DON'T put in modifier they act like they are locked when you turn.
They chatter and bind.
When modifier is added it allows it to slip, you can adjust the amount of slipping by adding a little to start with and working your way up.
This is also why when running most synthetics you don't need the modifier.


BTI

 

4X4 recommend 3 bottles to diff refill of 75w 140 synthetic fluid.. All others track lock diffs 2 bottles. Make a few 360 turns afterwards to get fluid into clutches.

 

When I changed my diff oil usd Amsoil 75w 90 and 3 bottles
of Amsoil slip lock add. Diff ran like new after this truck has 240k.

 

ha ha, kind of how it was explained to me in the beginning except the person used the sperm attaching to egg speak instead of the tadpole above.. lol

I made same mistake when I first got my 96 and that biatch felt like it had a full spool in the back until I went to Dodge and got the magic bottle of friction modifier. I was no crap dragging the inside tire on tight turns..

 

I would have too except I thought the profanity filter would have ***ed it
Friction modifier was originally made from sperm whale oil because of the properties, now it's synthetic. Some old timers still call it sperm oil though.

 

ha ha! That funny stuff!