how the heck am I suppose to know which particular Dana axle I have? I know it's a limited slip because it spins both wheels.
But seriously?!

 

Question number two: do I have to buy the friction modifier? Is there an off brand? Is it available at local auto parts stores, or only the ford dealer?

question number three: specifically what should I use for sealing the cover when I reinstall it? A decade ago I would use some sort of squeeze tube product that worked well. But I don't remember what that is,… And it's been over a decade. Please be very specific so I can go buy it.

thanks guys!

 

cant answer your last post but as the the axle... if you scroll down not quite half way (the numbers will start over) it says
Dana 60HD,,, 05-07 ford,,, 3.73 ratio,,, 4.10 carrier,,, 35 spline axle,,, C clip type
Dana 60 BOM Numbers | Dana 60 Identification

 

annaleigh has you covered in terms of what the differential is - The BOM number on that tag is 2002708-4

Dana 60, 3.73. - Axle Builder | Dana 60 Identification (BOM Lookup)

Hi-Temp Red RTV is what you use for this. You can even get gaskets, but you wanted to do this right away, right?

The one you want is the top of that long list.

You can buy oil that already has the friction modifier in it. What I would do is put the stuff in and drive it - bring it to a parking lot, turn the wheels all the way to one side, and take off without a lot of go-pedal and see if you get any chattering. If you do, add a little friction modifier, and keep doing that right up to the point where it doesn't chatter. Then leave it.

Ford Limited-Slip is notorious for being weak - in reality it's not weak, it just needs a little torque applied to it before it locks up - so one ice or snow, it tends to spin only one tire. On dry asphalt, it works. If you put the recommended amount of friction modifier in it, it'll be like an open diff. The trick is to add only enough to stop the chatter and then it actually works right.

I've used the oil that says it can be used for limited-slip diffs but it usually doesn't have the friction modifier, and if you buy the stuff that says it's already in it, it might be too much.

Understand that once you pop that cover, you have about 24 hours of cure time before that RTV will be good enough to put lube back in. At least, that's the only way I ever got it to not leak

 

BTW, found this:
I'd do that in a heartbeat.

 

Wow you two are tremendous help. TMI really: your answers overwhelmed me a bit until reading them a few times (and leaving work).

The reason I wanted to rush the project was because I wanted to get inside my diff ASAP and see what's up in there.
Because my van developed a strange vibration/drone at highway speeds (above 50-ish). It feels and sounds exactly like one long note from a rap song with a booming amplified speaker.
I have terrible tires (3 of them have 115,000 miles, and the 4th one broke a belt 2 months ago and I replaced it with a "new" tire with a 2010 manufacture date) so I figured maybe that. But all had good pressure and no bulges.
During the drone I popped it in Neutral- no change. I even shut off the engine at highway speed- no change.

The drone/vibe was all the way home- 50 miles on the interstate. Then again halfway back the same route Tuesday morning.

I believe if the issue is the gears then it would change depending on acceleration/steady/ or deceleration. But it doesn't. So I was thinking rear bearings.

And since i belive the oil in the rear was probably factory original (315,000 miles) I figured it's smart to get my eyes inside that diff and then replace the oil with new.

A mechanic friend of mine suggesting U joints. I checked them and didn't find anything damning. But then later it clunked 2-3 times shifting into gears.

 

i just bought it. I hope it comes quickly. I want to see inside my rear end.
Lol- yeah, I know how that sounded.

 

I learned way back when- that the friction modifier is not required and that it's just there to reduce noise (and prevent customer complaints and nuisance warranty complaints).

Krewat your post illustrates it as functional - "just enough then stop. Too much will make it not work.."

has as anyone else heard "my" theory?

 

When you checked the U-Joints did you have the rear wheels off the ground and the transmission in N? Do you have a 2 piece drive shaft? If so did you check the center bearing carrier?
Before jumping right in the differential I would do a few other things first.


1- Jack up the back of the van and put stands under the rear axle. Visually check the tires and wheels and spin them by hand to see how the bearings feel. Lift up on the wheels and side to side to check for any play. Listen for brake or axle bearing problems. Push up and down on the drive shaft really good around the pinion area to see if the pinion shaft bearings could be bad.
You might also want to have the rear tires balanced as it could be a tire out of balance.


2- Start the engine and put the transmission in gear and do a visual check while the wheels are turning. I am not sure about your differential but I read somewhere once not to reve the engine up too much with certain axles because you could damage it. Again I don't remember what axle that was. Seems it had something to do with one wheel freewheeling. My differential is a open diff and i can stop one wheel at a time while the tires are rotating. Listen for bearing noise.
Be sure and look at the tires and wheels while turning.

3- Remove the drive shaft to check the U-joints. Sometimes they can be dry/stiff and not really have any play in them. Be sure and mark the flange on the driveshaft and pinion yoke flange so you can put it back in the same position. If it has a center bearing be sure and check that too. Remove the wheels and check the rear brakes visually.

4- Before you remove the diff cover, check the diff fluid/grease level, could be low if you have a bad axle bearing seal. Visually check the ends of the axles for leaks.

5- Be sure and use a clean, preferably a light colored pan to catch the diff fluid/grease so you can inspect it for metal pieces or glittering sparkles. Once the cover is off, what are you going to look for? When i had my 85 axle apart I didn't really know exactly what to look for except chipped teeth on the gears, backlash on ring and pinion gear the ring.

https://itstillruns.com/inspect-diff...r-2313044.html

 

I wish I could chage the thread title to "sudden vibration undiagnosed" or similar.

Its been really bad. I checked the u joints in park on a level surface by applying hand torque to the drive shaft. I found nothing. Drive home and it was bad all the way.

This morning I brought it to my buddy's shop. He put it on alignment rack and brought me out to see it. The rear u joint moves up-down almost a quarter inch. Also they said the pinion is loose but I didn't see any movement.

He had the diff cover off and we looked inside. I've never seen so much wear on a gear set before. But when I touched it I couldn't feel any wear.
Ill get pics when I go back.

Him and his tech are blaming the bad motor mount and the hard shifting. ( it has an intermittent delay 3-8seconds, and then slams into Drive and Reverse).

Also so they are trying to talk me into new spider gears and the big fat pin. I'm skeptical. And he says the fluid is $30/bottle and that I need 4 bottles. im skeptical. But I do trust the guy and I know he wouldn't do me wrong. I'm just wondering if he has bad info.

Pics soon hopefully.

 

I would change the u-joint first and then take it to get a second opinion on the rest..

Bad u-joint can cause the pinion bearing to go bad.
Bad pinion bearing can cause u-joints to go out.
Bad pinion bearing can also cause wear on the ring and pinion gears.
Bad u-joint can cause clunk when going fro R to D

If everything is bad as he says, just let him rebuild the whole rear axle so it will be new again OR find a low mileage unit from the pull a parts

 

im with you on everything except the clunk. Mine the clunk is secondary- it has an unusual delay and then SLAM into gear. I've talked to Mark Kovalsky about it in detail and it is assuredly a transmission issue.
But yes I understand you are correct about the clunk.

Also I agree about doing the u joints and then taking a breath.

 

 

Hard to tell from the pictures and i am certainly no expert if I was looking at the gears.

I have been researching rebuilding my rear axle though and this is a good video below about removing the differential just to replace the bearings.
If you notice the first thing he does is to check the back lash.. I would think this would be a good way to check for wear on the ring and pinion gears..

The back lash on your Dana 60 should be .006 to .010. If you r gears are worn then you will have a lot more back lash then that.
Ring and Pinion Gear Set Up Specs - Torque and Backlash


Notice how he checks the checks the wear pattern. If you have a good wear pattern on the gear teeth and the backlash is within specs, then unless you have a broken or chipped gear, I don't think you would have a problem running it longer.

The spider gears, I don't know that much about them except to look for broken, cracked, or chipped teeth.

As to the pinion bearings, if they are bad then you can't really get an accurate backlash measurement until the bearings are replaced. I can't offer much advice on changing pinion bearings. I am learning how to do it and will be replacing mine if they're bad.. I simply am not going to pay someone $1500 to $2000 to do it for me when the parts would be under $300.00 to replace all the bearings in the whole axle.

 

Setting gears is more complicated than the average (or skilled) backyard mechanic can do. And the risk is too high if it's incorrect (safety and wasted money). I recommend you don't do that yourself. There's a lot of trial and error and "feel" to get it correct. I've read articles and talked to experts in detail about setting rear end gears.
The crush sleeve is finicky but has to be correct. And you can't just reuse it with new bearings and expect it to be correct. You can reuse it with your exact same old parts but even then there's room for error. And just a little too much torque on the pinion nut will crush it beyond spec.
In the world of local racing there's always some excessively wrinkled 50-year old guy with a cigarette hanging off his dirty lips that does it for $150 cash. Also in the world of local racing the rear ends always last exactly 3/4 of the season and then break.

im leaning towards getting the $300 junkyard axle with 130,000 miles. It should get me through another 50-75,000 miles... I'll update the other thread about this.