Mileage and limited slip differentials

[Lefty]

I'm thinking about installing a limited slip in my 2WD 3.0 liter 8.8 4/10 Edge. I would imagine that I will have reduced mileage. Does anyone out there know what differences I can expect?

Also, I do not intend to buy an old junkyard axle or even a new differential. It just seems like overkill. I'm hoping to crack open my own differential and simply install a new OEM limited slip assembly. Does anyone know of a reliable source for the parts?

 

[Uncle Gump]

Changing the carrier is doable.

Ever set up a rear end before? They require some special tools.

 

[Lefty]

My friend put a limited slip in his Mustang. We think that he has the know how and the tools.

 

[gw33gp]

I have never heard of a LSD causing reduced gas mileage, if that is what you are talking about. The only time it has any affect is when going around corners and the drag at that point is very minimal. The scrub of the tires while going around the corner should have more drag than the LSD.

 

[RonD]

+1 ^^^

No change in MPG unless differential was setup wrong, i.e. a howling noise when driving, indicating too much friction
Since you have to pull the axles plan on new bearings and seals

Differential cover didn't have a gasket from factory, they just used RTV, but you can get a gasket if you want
Check the Vent tube/hose, make sure its clear, you can get small filter for the end of the hose under the bed, should have one on it now
Clear vent helps to prevent leaks as it allows pressure in the axle housing to equalize as the oil heats up and expands

 

[don4331]

I'm thinking about installing a limited slip in my 2WD 3.0 liter 8.8 4/10 Edge. I would imagine that I will have reduced mileage. Does anyone out there know what differences I can expect?

Also, I do not intend to buy an old junkyard axle or even a new differential. It just seems like overkill. I'm hoping to crack open my own differential and simply install a new OEM limited slip assembly. Does anyone know of a reliable source for the parts?

@Lefty : Just to be clear here - the limited slip carrier and side gears are different from the non-limited slip ones. So, you will need limited slip carrier, matching side gears, limited slip clutches and "Z" spring. I usually get everything but the clutches from another axle (i.e wreckers) as they're not really wear items; clutches come from Rockauto or similar.

Procedure:
Undo the cover and drain oil, remove cross pin (5/16" extra long box end wrench - its locktite in), remove c-clips, pull axles. Then undo the carrier caps (make sure you keep drivers on drivers side, passengers on its side) and remove.
Transfer your ring gear to the limited slip carrier (ring & pinion are a matched set, a little heat is often handy here - propane torch not hotter), install the carrier, setting it up correctly. 90% of time, the shims used at factory are what you need, but there is the other 10%....

If you decide on new bearings for your limited slip carrier, you need a bearing puller and press. (and it just about guarantees shims are off...)​

Then you install clutch pack (having soaked them in friction modifier) and limited slip side gears.
Slip axles in, install c clips, spider gears and cross pin.
Compress the "Z" spring and insert it into carrier to set the preload on the clutch packs. I think there is colourful language required here when spring slips out of clamp before it is quite in, and goes into low orbit)
Button it up with the rear cover and add oil and friction modifier.

Optional: axle end bearing and seals, rear brake hardware (pads, cylinders, etc anything that needs doing while you are there).

 

[Lefty]

Thank you for adding clarity to this job, especially because I'm a rookie!

 

[dvdswan]

Thank you for adding clarity to this job, especially because I'm a rookie!

hmm, I thought you were a lefty...

 

[don4331]

Thank you for adding clarity to this job, especially because I'm a rookie!

Wasn't sure if you're a rookie or not, but others ghost the site for information. I wanted to make sure they got all the information they would need.

 

[Lefty]

Wasn't sure if you're a rookie or not, but others ghost the site for information. I wanted to make sure they got all the information they would need.

I gotta say that I came to this site because I soon found out that much of the wisdom here is solid. This is a very good group.

 

[lil_Blue_Ford]

There is another option too, the Detroit TruTrac. It replaces your differential with a geared limited slip, no clutch packs to wear out.

My F-150 has a Lock-Right locker in it. Not the best street manners, but it goes.

My first Ranger got a junkyard limited slip, just used the tech library to figure out what gears I had and what the axle codes were for the limited slip version. Worked well.

My choptop has a limited slip from a donor I bought that had extra clutches installed as per the tech library. Makes it work more like a locker but a little nicer on the street. The Tru-Trac works like that, but without clutches.

I’m currently working towards getting a limited slip out of a donor I bought ready and under my green Ranger. That will get extra clutch packs.

 

[ekrampitzjr]

Absolutely change all bearings and seals while it's apart. That includes the axle bearings and seals at each end by the wheels.

The cost of those parts is minimal compared with the hassle of pulling out the axles again later.

Remember you will need to add limited-slip additive to the fresh diff lube after the conversion.

When you were asking about mileage, were you actually asking how many miles the limited-slip will last compared with an open diff? I understand limited-slip clutches are a wear item, so that is a potential issue over many miles.

 

[lil_Blue_Ford]

Absolutely change all bearings and seals while it's apart. That includes the axle bearings and seals at each end by the wheels.

The cost of those parts is minimal compared with the hassle of pulling out the axles again later.

Remember you will need to add limited-slip additive to the fresh diff lube after the conversion.

When you were asking about mileage, were you actually asking how many miles the limited-slip will last compared with an open diff? I understand limited-slip clutches are a wear item, so that is a potential issue over many miles.

Some synthetic lubes and stuff come with the additive in it, so you kinda have to pay attention when you buy the gear oil if it will need the additive or not. I have synthetic gear oil going in mine that says on the bag (yes, it’s in bags not bottles) that no additional additive is needed

 

[Lefty]

Some synthetic lubes and stuff come with the additive in it, so you kinda have to pay attention when you buy the gear oil if it will need the additive or not. I have synthetic gear oil going in mine that says on the bag (yes, it’s in bags not bottles) that no additional additive is needed

I've had my share of problems with vendors. I've often got the wrong parts. I wonder is you could recommend someone who might have the right parts for sale. I've got a 410 8.8 differential now.

 

[lil_Blue_Ford]

I've had my share of problems with vendors. I've often got the wrong parts. I wonder is you could recommend someone who might have the right parts for sale. I've got a 410 8.8 differential now.

Ok, so IMHO, your easiest solution for upgrading to a limited slip is to get a junkyard axle and swap the whole thing. A K6 or R7 axle code on a Ranger door sticker is 8.8” limited slip 4.10. (I have the axle codes section of the tech archives saved on my phone for junkyard searches). Little more difficult swap would be an Explorer 8.8 which would give you disk brakes in the rear. That would be a D2 axle code for 4.10 LS.

Unless it was impossible to find the ratio I wanted or I was going to go with something like the TruTrac, I would likely just swap the entire axle and skip messing with setting up gears. If you’re just going to use the differential, you can use any LS diff from an 8.8 Ranger since you will re-use your gear set. An Explorer 8.8 uses 31 spline shafts so you have to use the entire axle. Your gear set could be swapped to one though. The TruTrac and ones like it would have to come from a place like Summit Racing or Jegs or JC Whitney or something.

I got my gear oil from Autozone. Think what I got for my green Ranger was Pennzoil synthetic stuff. Since I’m re-doing the axles and it’s going to be a bit of a go fast toy, I went synthetic. For most of my axles I just use regular gear oil though and buy it by the 5 gallon bucket…