3L55

"Rusty Vandura - www.tinyurl.com/keepoppo" (rustyvandura) 02/20/2020 at 11:39 • Filed to: None

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From a snowier clime... 3.55 Posi, $400 delivered by LKQ. I had to pick it up from my friend’s shop. We pulled the cover and the innards look and feel good. 155k miles. What should I fill this with, specifically ? 75W90 with a friction modifier?

HammerheadFistpunch > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 11:48

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75w90 with lsd modifiers is a good choice. Truthfully a posi w ith 155k probably needs new clutches.

Demon-Xanth knows how to operate a street. > HammerheadFistpunch 02/20/2020 at 11:51

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Agreed there. Take the axle to a gear and axle shop, have them swap out the clutches and do a servicing. They’ll love being able to have it on a bench instead of underneath.

Rusty Vandura - www.tinyurl.com/keepoppo > Demon-Xanth knows how to operate a street. 02/20/2020 at 11:53

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I think that’s about $900 labor.

Rusty Vandura - www.tinyurl.com/keepoppo > HammerheadFistpunch 02/20/2020 at 11:55

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With LSD modifiers already stirred in, or added afterward? The guy at the shop where I had this delivered said he’d use a 75W90 synthetic and also add some modifier.

HammerheadFistpunch > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 11:56

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You could probably do a rebuild on your own. You’d need a kit like this

https://www.summitracing.com/parts/fms-m-4700-b

The reality is that these types of diffs need to be rebuilt every 60-80k

HammerheadFistpunch > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 11:57

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I guess Ford wants you to use their  Motorcraft XL-3 modifier

Rusty Vandura - www.tinyurl.com/keepoppo > HammerheadFistpunch 02/20/2020 at 12:05

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The kit you recommended includes some modifier... I’m studying YouTube right now on this...

HammerheadFistpunch > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 12:05

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Don’t take my word for the kit being the right one, but I think it is.  I don’t know Ford well.

Rusty Vandura - www.tinyurl.com/keepoppo > HammerheadFistpunch 02/20/2020 at 12:10

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Do you know anything about a “bellview” washer setup?

Demon-Xanth knows how to operate a street. > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 12:12

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When I had my pinion bearing replaced on my Dakota and the LSD clutches serviced in 2013, that sounds about right. But then it’ll be good for another 100k+ miles. That said, if you keep the shims and such in proper order and are careful, you can probably do it yourself.

Gone > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 12:14

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S ynth 7 5W -140 w/4oz XL-3 or Currie CE-5012. I don’t think the 140 vi sc come with FM like lower visc lubes do (9 0 usually does) .

P robably needs clutches by now anyhow (add the extra one if you rebuild).

Rusty Vandura - www.tinyurl.com/keepoppo > Demon-Xanth knows how to operate a street. 02/20/2020 at 12:15

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If Hammerhead is correct, a clutch kit for this thing costs about $75 at Summit. There’s a kid who swaps them out on YouTube and it looks like a doable thing. It might not be a bad idea for me to do that before I install the rear end. I don’t have any reason to think that I’d lack the skills to do it myself, based upon what I’m seeing on YouTube. Crush sleeves and all that, probably not, but this, maybe...

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/20/2020 at 12:16

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Do you have experience replacing the clutches in one of these? I’ve wrenched plenty over the past 35 years, but never fooled with a differential. 

HammerheadFistpunch > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 12:20

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So long as it can go back together without having to reshim or reset the lash, I think it would be pretty easy

HammerheadFistpunch > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 12:20

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I don’t

Rusty Vandura - www.tinyurl.com/keepoppo > HammerheadFistpunch 02/20/2020 at 12:26

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That’s my take as well. I’m struggling a little bit because I know zero  about any of this and I’m talking to folks and assembling the info as I get it. From what I understand, if the replacement parts are FoMoCo, then you can count the existing shims and make sure you use the same number upon reassembly and yes, it looks pretty easy to me, too. I’m just thinking maybe I’m missing something... But this would probably be easier with the diff sitting on the ground, than up underneath the car.

MM54 > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 12:42

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At 200k the LSD in my p71 was still kicking, but definitely check out the clutches while you’re in there. They can get very worn and allow the axle shaft to walk in and out which makes the rear brakes wonky (as mine did) while still locking up the axle just fine . I don’t believe it’s particularly difficult to replace them.

As for oil, I used 75 w140 synthetic, which had the friction modifier in it already. 75-90 is probably okay but the heavier stuff is recommended with heavy loads or long trips at higher speed (aka when the diff gets hot) . Factory fill for police applications would have been the -140.

Gone > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 12:44

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I’ve done a couple, it’s really not bad. Just need tools and patience. Also cursing and smashing your fingers accidentally.

Not a terrible video below. He did the standard config (CSSCSSC) vs extra clutch (CSCSCSC) w/CF clutches. I always use the standard kit. If you don’t want to buy another clutch kit you can save the best two old clutches as your extra clutches. I’ve heard of people leaving out the S-spring as well, but I’ve never done that. Supposedly reduces lift throttle oversteer, but no experience. It’s a bit easier out of the car, but not bad in the car. He didn’t put the spiders back the same either but oh well lol.

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/20/2020 at 12:51

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I understand that there is also the matter of a “belle ville” washer... I guess that some people like to do away with the Bellville washers...

Do I understand correctly that you can use an extra clutch on each side and fewer shim washers to compensate? But that you’d need to buy a second shim kit in order to gain the extra shim for each side? Do you think the Ford dealer might have single shims? (Probably cost as much as an entire kit...)

Gone > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 13:21

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Yeah, I’ve always put the cross pin spider bellevilles. Pretty much OEM rebuild w/alternate clutch stack.

Re: clutches, mentioned above but better explained. When you pull the old clutches out, save the best two for the extras. If they’re all trash you’ll have to get two clutch rebuild kits, otherwise you only need one kit.

MFE wrote up a good how to longlong ago, so I had to go find it. Copypasta:

It helps if you have a good manual but the instructions that come with
the kit are pretty good. The part number is F5AZ-4947-BA and it’s generally around $70 or so at Ford dealers. You may be able to find it cheaper on the net. Get about 3 quarts of 80w-90 gear oil. If you use synthetic you probably shouldn’t use much friction modifier. If you want absolute max trak-lok action and are willing to put up
with some unsettling noises from the rear end, don’t use any modifier at all. It just makes the clutches more slippery so they don’t chatter. I chose to use half a bottle the last couple times and I’m glad I did since this is my daily driver, autocrossed and dragraced for fun. Anyway, here goes.

1) Jack up the rear end and support with stands.
2) Loosen the diff cover bolts, removing all but the top two so you don’t take a gear-oil bath
3) Pry the cover loose and drain the rear into a pan.
4) When threat of bathing is gone remove the top bolts and pull the cover off
5) Scrape/wipe out the bottom of the diff.
6) Now is a good time to soak the new clutch discs in friction modifier, the need to soak for 20 minutes at least. If not friction
modifier, at least gear oil — you don’t want to put them in dry
7) The shaft going through the center of the diff is called the pinion shaft. It’s got a lockbolt on one end. Undo the lockbolt and push the shaft out. You’ll only want to push it in a little bit so you can still rotate the assembly and pull it out toward you. There isn’t enough clearance to push it all the way through or to turn the assembly if you’ve tried.
8) Remove the wheels and brake drums, leave the other brake hardware alone. Push the axles inward, and you’ll see the c-clips that hold them in place. Remove the clips and pull the axles out gently — don’t torque the bearings on the way out and don’t let the axles hang, just remove them.
9) Get a grip on the s-spring and pull it out. You may need to punch it with a hammer to get it started, and keep a damn good grip on it when you remove it you don’t want it zinging around.
10) The gears you see are the pinion gears and the side gears, called spider gears. Rotate things until the spider gears pop out, then pull the pinion gears out too. Inspect for damage.
11) Now you can simply slide the clutch packs out, use the tabs on the plates if necessary. Make sure you get them all out including the shims.
12) Reinstall the clutches and steels in the proper order, using a shim at least as thick as the ones you removed. You want to use the thickest shim you can while still being able to get the spider gears back in. Forget about using the set-up tool and all the special measurements, if you can get the spider gears back in you’re all set. Note: Each clutch pack is made up of a series of Frictions and Steels and in the factory order they go F-S-S-F-S-S-F. However, if you re-use the best two of your old Frictions in place of one of the new Steels you can re-stack them in an order that makes the diff lock better, which is F-S-F-S-F-S-F, which is the same number of total elements. You may have to trial assemble it a couple times to get the right shim so it’s just loose enough to get back together, barely.
13) To get the gears in, it helps to have a helper turn the now-temporarily-installed driver’s side axle while you lock the passenger-side pinion gear in place. The spider gears will squeze into place. They are perfectly aligned when you can get the pinion shaft back in.
14) Re-install the s-spring. Or don’t. It’s only there to help in really really low-traction situations. Leaving it out will not hurt the locking power of the unit under normal conditions. Getting it in, if you choose, can be a bitch. Try holding it against its slot with a pair of channel-locks to get it squeezed down a bit while prying it in with a piece of 2X4 using the swaybar as a fulcrum. Alternately, do the same but whack it with a mallet. It should pop in. If it doesn’t, try using a 1-1/2 inch hose clamp to squeeze the spring so you can insert it. Then cut the clamp and slide it out.
15) Re-install the axles by pushing them all the way in, installing the c-clips, and pulling the axles back out against the clips which are now recessed in the housing and locked in place.
16) Reinstall the pinion shaft and make damn sure you put it in the right way so the new lockbolt can be installed. And do not use the old lockbolt.
17) Use gasket maker on the diff housing and reinstall the cover.
18) efi85gt posted a terrific tip for filling the diff. Forget the fill plug. Let the rear end drop as low as you can and remove the little vent cap on the top of the right side axle tube. Clean the area around it carefully and you’ll be able to fill it through this hole with a fraction of the stinky mess you get when you use the “fill hole”. Looks like this:

But you should still remove the fill hole bolt so you know when to stop filling, which is as soon as it starts to come out that hole. Wipe the tip of the bolt off, it’s magnetic and the silvery paste is metal shavings.
19) Fill the housing until it comes out the fill hole and replace the plug.

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/20/2020 at 13:43

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Thank you for this. Also, the YouTube video was pretty good, made the thing look very doable. I’ll give the Copypasta above a read.

Thank you for taking the time to share your knowledge with me on this.

Gone > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 14:08

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Welcome. It’s not that bad, helps to have a friend though. Vise grips work well on the S-spring, but hose clamp method works well too. It will wreck things (like your face ) if it gets loose though, so seriously be careful. Using the ax le to turn the spiders in place is a neat trick (MFE how to ) if you have help (or decent reach ) , m ainly bec au se those spiders wil l eat your fingers. The guy in the video is so lucky when he reassembled his   lol .

Worst thing that happens is you take it to someone to button it up. Or find a local Mustang/Jeep guy to help . Shouldn’t be near full rear end rebuild pricing at a shop . It’s a couple hours labor if you’re methodical about it.

Good luck!

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/20/2020 at 14:25

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Oh, I feel more than inclined to take it on myself. I’ve turned more than a few wrenches over the past several decades. Besides, this entire project is highly ill-advised and I have acute buyer’s remorse as it is, so saving a few hundo by doing my own labor is seriously indicated.

Looking at the YouTube video, it appears that there are two washers — shims? — side by side on each side of the carrier that have no clutch between them. Is this where you’d place the additional clutch? Thing is, that would increase the thickness of the pack by something like 0.10" on each side. Would the play in the spring allow for that? Doesn’t seem like there are any extra shims to get rid of. But an extra clutch, if there’s room for it, seems to make a lot of sense.

What’s your line of work? If you’ve paid any attention to me in this space, you might already know that I’m an 8th grade math teacher. Who wrenches and builds and gets too worked up about the state of American politics.

Rusty Vandura - www.tinyurl.com/keepoppo > HammerheadFistpunch 02/20/2020 at 14:35

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I can’t find any of the email messages that you and I shared. Would you mind dropping me a line at your convenience? I want to ask you about something non-Oppo.  Thanks. oliphant.chuckerbutty@gmail.com

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/20/2020 at 15:52

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Any thoughts about the clutches with carbon fiber instead of the standard?

Gone > Rusty Vandura - www.tinyurl.com/keepoppo 02/20/2020 at 16:37

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You just stack them spider clutch steel clutch steel clutch steel clutch case (4 clutches, 3 steels, 7 total) instead of spider clutch steel steel clutch steel steel clutch case (3 clutches, 4 steels, still 7). Should come out a little thicker stack, but not much and the S-spring is just compressed a bit more. If you swapped to the F-150 S-spring (stiffer/thicker), it becomes a bear to get in there but is possible.

The carbon fiber stuff was super new (lol!) when I moved off the Mustang stuff - it was only just out (‘03-’04 Cobras had them). If the price is close, that’s the way I’d go. I would think the clutches last longer and hold more power before they slip.

As for me, I’m a MechE currently in offshore O&G. I bore easily so I industry hop lol . I’ve dabbled in cars since I was a little kid with my dad. Met a bunch of motorsports folks, went all over to races, etc becuase my dad’s job. Haven’t had a car for fun in over 10 years now though, so I have a lot of old knowledge lol. But in a previous life I dabbled in all of it - drag/bracket racing, Jeeps/mud/rock buggies, moto-x, street bikes, auto-x/track days.

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/20/2020 at 17:08

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So, an uncivil engineer? My friend’s son is an engineer working for Exxon and they had him working in Belgium for a couple of years and he was pulling like three bucks in salary. I’ve always been curious about what life aboard an offshore rig might be like.

Do you have access to a Netflix account? Check out a show called Last Breath . Phenomenal.

I’ve been dabbling by proxy by watching Roadkill, Roadkill Garage and Hot Rod Garage, but they are losing their innocence as they try to do too much and I fear I will tire of them.

I see that in the written instructions you provided, the writer goes into the clutch/steel patterns and explains all of that. I haven’t read yet...

I’ll keep you posted on Crappy Vic.

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/21/2020 at 12:00

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Good morning.

Here’s a grab from the YouTube video, and the text from the Copypasta and a s I study both, I can’t get it to make sense. Basically, seems to me, you’ll wind up with a Friction riding against the backside of the gear itself.

Thoughts?

!!! UNKNOWN CONTENT TYPE !!!

Gone > Rusty Vandura - www.tinyurl.com/keepoppo 02/21/2020 at 12:31

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I should have watched closer. Ordering on the removal and reinstall is wrong lol. It was mentioned it’d been rebuilt before and he just continued with the incorrect stacking. Clutch goes again st the pinion gear and the shim (just like the text). Here’s how the stock system *should* be stacked.

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/21/2020 at 12:50

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That’s good. Means I’m doing my studying , right?

I’ve been studying how LSDs actually work, and it seems to me one also might refer to the thing as a thrust or torque balancer . As I understand it, under accel eration, the forces will be spread equally between the two driving tires or wheels and both will be accelerating the car simultaneously. So the LSD is in operation constantly, but there’s just minuscule or nonexistent slippage the vast majority of the time. Sound right? I was thinking that the LSD rear end was a one-legger until the one leg slipped and it became then a two-legger. Makes more sense now, if I have it right.

Also, on Netflix :

These guys are working on a manifold at the bottom of the North Sea when s**t goes haywire. Truly an excellent account. I’ve watched it twice and there’s a good chance I’ll watch it again, at least once.

Gone > Rusty Vandura - www.tinyurl.com/keepoppo 02/25/2020 at 11:34

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So busy with things....

G ood catch on the vid .

With d ifferentials, it depends on the type. GM (Gov -lo k/G80/ Eaton whatever you call it) is open until it sees a high wheel speed differential (~ 100+ rpm differential), and the wheels lock (harshly). The diff works well mostly, except can explode - Gov bomb. Neat diff except for the booming.

Clutch diffs (commonly called LSDs) are usually engaged all the time until the wheel speed changes then the clutches allow the speed differential to happen. So you are correct . :)

People throw terms around and they get mixed up. There are also the biasing diffs which work different as well.

I’ll have to check it out when I get free time (LOL!). Dive work always seems sketch. Work class ROVs are where it’s at. Rigs and boats are fun to visit (go out a few times a year) , but wouldn’t want it to be a permanent thing...   :)

Rusty Vandura - www.tinyurl.com/keepoppo > Gone 02/25/2020 at 13:29

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Thanks for the note. “Last Breath” is worth the time, good human drama.

The standard, open diff, I now fully understand and it really is an elegant solution.