NPoCP: Differential Equation Edition

"Rusty Vandura - www.tinyurl.com/keepoppo" (rustyvandura) 01/31/2020 at 16:55 • Filed to: None

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A local dismantler offers a 3.55 LSD rear end from an ‘06 Vic for $875, out of the car. Shipped from Oregon... NPoCP?

MKULTRA1982(ConCrustyBrick) > Rusty Vandura - www.tinyurl.com/keepoppo 01/31/2020 at 17:08

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I’m sure I don’t know, but hubs as well delivered to your doorstep? 

RamblinRover Luxury-Yacht > Rusty Vandura - www.tinyurl.com/keepoppo 01/31/2020 at 17:13

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To be much good as an LSD, it likely requires a rebuild. If it’s intended to go in the Vic, since you’d likely have to assemble it out of one casing and into the other, I’m not sure you get much other the gearing advantage vs. buying an LSD center - but an advantage it is.

Although - brand new 3.55 gears are $160 out of Summit as well, so...

Edit: missed that it’s already a Vickie axle. Some of the point still stands - if it needs clutch rebuild, the advantage over new gears and new center on the one you’ve got is a question.

Rusty Vandura - www.tinyurl.com/keepoppo > MKULTRA1982(ConCrustyBrick) 01/31/2020 at 17:14

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That’s a good question. I may need to drive 15 or so miles to pick it up. Also haven’t checked LKQ yet.

XJDano > Rusty Vandura - www.tinyurl.com/keepoppo 01/31/2020 at 17:26

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Check LKQ, I was looking for an F250 super duty Dana60 and it was under $500. For just the axle, not including shipping and whatever taxes. 

atfsgeoff > Rusty Vandura - www.tinyurl.com/keepoppo 01/31/2020 at 17:29

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If it’s the factory clutch type LSD, I say pass. Spend $5 00 on an eaton true-trac mechanical torsen diff, no parts to replace from wear over time. Get it installed professionally for another $400 or so.

XJDano > XJDano 01/31/2020 at 17:30

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Holy crap.

https://www.lkqonline.com/2006-Ford-Crown-Victoria-83-up-Axle-Assembly-Rear/-h%257CDKjmncOPD

$700 and $800+

Rusty Vandura - www.tinyurl.com/keepoppo > RamblinRover Luxury-Yacht 01/31/2020 at 18:05

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Yes, ROI. This one is already Vic, and has 50k miles on it, according to LKQ. If I had the gear shop rebuild it, they’d do so with the diff still in the car.

So, seeking your opinion: what gearing would you use? I’m notched at 3.55 because it’s a bit higher than the 3.27 already there, and it was a factory option. But if I’m changing gears anyhow, some have mentioned the 3.73. I don’t want to entirely chop the legs off this car.

Rusty Vandura - www.tinyurl.com/keepoppo > XJDano 01/31/2020 at 18:06

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Yes, I did that search as well, and the part the salvage yard quoted me may very well be the one out of Salem Oregon that’s showing up on LKQ.

Rusty Vandura - www.tinyurl.com/keepoppo > atfsgeoff 01/31/2020 at 18:10

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But then, there’s gearing. I’m at 3.27 now, which is a bit tall. I’m stuck at 3.55 because it was a factory option and the differential I mention here is a factory axle in that ratio with the LSD. My local gear shop, who is extremely expert, if he’d even do it, would rebuild the axle with it still installed in the car. I haven’t gotten a quote from him yet.

What gear ratio would you use? 3.27 (open) was the most common, with the 3.55 LSD an infrequently ordered option, and some 3.73s, also open. I’m afraid that on the highway, at 80 mph, I’d be finding the 3.73 a little short. (Here’s where the old-timers begin talking to me like I’m stupid, telling me that I can’t have it both ways...)

atfsgeoff > Rusty Vandura - www.tinyurl.com/keepoppo 01/31/2020 at 18:15

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Crown Vics have had some harmonic vibrational issues at higher speeds with their driveshafts when running shorter rear ratio.

I would personally stick with 3.27. That’s what my ‘92 Crown Vic had with the Handling/Performance package and it was great. Then again that ‘92 weighed about 500 lbs less than a 2000+ model. I would under no circumstances go any shorter than 3.55.

Rusty Vandura - www.tinyurl.com/keepoppo > atfsgeoff 01/31/2020 at 18:39

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Good to know about the driveshaft issue. Guy at the gear shop opines that a switch from 3.27 to 3.55 isn’t worth the effort because only about an 8% gain. I’m thinking that 3.55 is where I wanna go because even without the driveshaft thing, I’m afraid 3.73 is going to feel kind of short, and California has some long, straight stretches of Interstate.

XJDano > Rusty Vandura - www.tinyurl.com/keepoppo 01/31/2020 at 18:56

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Also try row52.com that’s a network of upull type places.

This is by me, not sure if you can look up the gear ratio by vin.

https://row52.com/Vehicle/Index/2FAFP71W76X147823

RamblinRover Luxury-Yacht > Rusty Vandura - www.tinyurl.com/keepoppo 01/31/2020 at 20:44

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3.55 is probably a good compromise gearing. Not obliterating the stock mileage, but still enough lower to spin a wheel.

My own Galaxie has a 3.25, and I drive everywhere in "starting second", so it's hardly crippling as is, but I can see the appeal of "fun times" ratios. 

It very well might have enough friction material to use as is with a mere 50k... I'd expect about half worn out. 

Rusty Vandura - www.tinyurl.com/keepoppo > RamblinRover Luxury-Yacht 02/01/2020 at 01:42

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Do those clutches wear out in normal driving?

Rusty Vandura - www.tinyurl.com/keepoppo > RamblinRover Luxury-Yacht 02/01/2020 at 14:36

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What Are the downsides of running with a spool? Seems like it would be the cheapest alternative...

RamblinRover Luxury-Yacht > Rusty Vandura - www.tinyurl.com/keepoppo 02/01/2020 at 15:15

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LSD clutches do wear out in normal driving, yes. The clutches are always in some degree of contact, and ordinary rate differences between left and right makes for wear.

As to the spool question, the downsides are tire destruction and much greater likelihood of breaking the whole back end loose, particularly in rain. Not to mention some increased difficulty in steering. I wouldn't do it.

Rusty Vandura - www.tinyurl.com/keepoppo > RamblinRover Luxury-Yacht 02/01/2020 at 22:58

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I'd have thought stress on the axle shafts would be a thing as well.