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Limited Slip Differential Conversion

 
Old 01-14-2019, 01:28 AM
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I have a 2002 5.4 L V8 with an open differential. Is it practical, and at that possible, to convert it to a limited slip differential or should I just look for a different truck?
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Old 01-14-2019, 02:39 AM
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Originally Posted by glen d View Post
I have a 2002 5.4 L V8 with an open differential. Is it practical, and at that possible, to convert it to a limited slip differential or should I just look for a different truck?
Well, yes its easy

But not cheap necessarilly. If gonna pull diff, might as well put in new bearings and seals too. Diff $400-500, labor $500, bearing kit $250.


Cheapest is replace whole rear axle with one from junk yard (w/same gear ratio if 4wd). Problem is , the factory l/s is likely worn out and needs clutches changed.

Factory l/s wears out fast...by 50k most are useless. So plan on rebuilding that

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Old 01-14-2019, 02:42 AM
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Is this a job that could be done at home or would a shop be the best way to go?
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Old 01-14-2019, 03:29 AM
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You can swap a whole rear axle at home in a few hrs.

Changing out differential can be done home....by a person that is meticulous and can follow directions, with right tools, patience, Including case spreader, dial indicator, bearing press. If you have to ask, your not that person.

With improper ring/pinion gear face contact pattern, gears will be noisy, wear rapidly and self destruct in a couple thousand miles, taking out everything with the debris. Gears, differential, bearings, and possibly even axles by wearing the bearing surface.

I got to watch my wifes little brother do that to his truck when he was 16. Broke a gear tooth, didnt have money to pay to get it fixed so tried to do it himself from junkyard parts. Lasted very short time. It was ....entertaining. Dumbasses only listen to other dumbasses that tell them what they want to hear.

When it comes to gears/differentials.....thats money well spent by seeking out THE BEST person in your area. A poor job can cost you $$$$

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Old 01-14-2019, 03:54 AM
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But......its also not unheard of...that when only replacing a differential, and NOT changing gears, that when the new diff is installed....using same shims.....no gear contact adjustments are needed. But need to be prepared to totally reset the diff in case.
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Old 01-14-2019, 04:58 AM
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Thanks for the advice, I will save up the money and look for someone who can do it confidently. I am in no hurry to do this, nor does it really need to be done but it would be useful for hunting during winter, and winter driving in general in my area. I'm not about to completely trash my truck and hear about it for the rest of my life for something that isn't completely necessary.
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Old 01-14-2019, 09:13 AM
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As long as you don't remove the pinion, it should be pretty easy. If you remove the pinion, you'll have to have the gears set up again.... which isn't exactly a beginners job. Like MBB said, keep track of the shims, and how they are installed.... and you can do it pretty easy. This is a really good video on disassembly, and reassembly of an 8.8 - which is quite similar to a 9.75 is. Not the exact job you are doing, but still a very beneficial watch.

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Old 01-14-2019, 02:12 PM
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Originally Posted by glen d View Post
Is this a job that could be done at home or would a shop be the best way to go?
Yes, it can be done. I did it myself on my 8.8 a few months ago, and I am by no means a master mechanic. Bought a junkyard axle, replaced axle shafts, bearings, and seals, replaced open diff with LSD, and swapped it into my truck. Heard a lot of horror stories about how easy it was to screw up, but it wasn't really that hard. That said, you have to be able to follow instructions carefully, or bad things can happen.

IMO the key factor is whether you reuse the ring and pinion gears. If so, then your axle should already be set up with the correct gear positioning, and it is relatively easy job. If you change the ring and pinion, it is a much harder job, because then you get into adjusting pinion depth and carrier backlash to get the correct gear pattern.

If you want the same gear ratio, I recommend rebuilding your axle. No need to buy a new one; put those dollars towards the LSD carrier. If you want to change the gear ratio, I recommend buying a salvage axle and rebuilding it.

Either way, you should plan on rebuilding it. It doesn't make the job much harder, and you will have a nice new axle good for at least 100K miles.

The job is way easier with the axle off your truck. Once you pull the axle and tear it apart, you are committed, so if this is your daily driver and you gotta get to work on Monday, that is a factor in your decision. If you are rebuilding a junkyard axle then you can do all the work on the axle and then easily swap it in a weekend.

Costs for an 8.8 are $300-600 for the LS differential carrier, depending on whether you go OEM or aftermarket, $100 for a rebuild kit, $250 for axle shafts if needed, and $300-500 for a salvage axle if needed. Plus $100 for tools and $50 to have a machine shop press the bearings on your carrier.

If you wanted to do the absolute lowest cost job, you could get a used LSD carrier from a salvage yard for $100, and replace the clutch plates and carrier bearings for about $100 more.

OEM Ford LSD is actually quite a bit cheaper than the aftermarket options. Some of the aftermarket choices, such as Yukon and Eaton, are said to be more durable and have higher bias ratios (how much power they can redirect to traction tire). I went with an Eaton TrueTrac, which uses gears instead of clutch plates, so it does not need friction modifier and does not need to be rebuilt. I think it performs awesome and I am super happy with the results.


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Old 01-14-2019, 02:35 PM
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your workspace looks like mine - too much stuff / not enough space
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Old 01-14-2019, 03:29 PM
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Originally Posted by glen d View Post
I have a 2002 5.4 L V8 with an open differential. Is it practical, and at that possible, to convert it to a limited slip differential or should I just look for a different truck?
It's practical and simple, but many ways to screw things up. You can get a complete LS diff with clutches already installed through the internet for about $250. Carrier bearings are about $20, I think. All you need to swap is the diff and the ring gear. If you're lucky the diff is still centered like the factory open diff and doesn't need reshimming.

Seems like a guy could take his internet diff and bearings to a decent truck-oriented shop and have it installed and lash set or verified for $100-200. Total cash outlay under $600 maybe, after new fluids and labor. All of the work is done through the diff cover and the wheels. Nothing really big or heavy to deal with, just time under the back end. If it wasn't for the worries about proper lash setting it would be just a simple large part swap.


One option. Probably depends on what part of the country you live in. If you're in the rust belt then swapping the complete housing, axles and diff has to be done through the rusty bolts and nuts, plus dealing with the brakes, shocks, and other stuff. Seems simpler but more stuff to break or go wrong.
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