Abusta

Hello I'm looking to upgrade an open diff 94 2wd f150 to a limited slip set up from the original open diff. Anyone have experience with this and know what it would cost to do it properly?

I'm bringing a socal truck into the northeast the open diff will definitely leave me stranded at some point.

Screwed05

To do it right.
New FRPP LS 31 spline carrier is $260
FRPP Ring gear install kit $100
Gear lube $30-$60 plus a bottle of friction modifier if not already in the lube.
All from Summit

Labor is probably about $200, but not sure I do my own.

Abusta

You think it's something that could be tackled with hand tools and youtube? The diff hasn't been touched in years. Would it add significantly to the labor cost of servicing the diff ?
Thanks

Screwed05

It's a fairly simple swap, and most everything can be done with hand tools. Except, the Ring bolts may need to zipped off with an impact, you will need need new bearings pressed onto the new carrier. You can try freezing the carrier overnight, heating up the bearings slightly, and tapping them on. You can heat the Ring slightly as well to get it to drop in place, otherwise. The Ring will need to be knocked down into place with a dead blow hammer. Don't pull the Ring in place by tightening the bolts.

When you pull the old carrier out there will be shims on both sides keep track of these and which side they came from. You will need to paint a section of the ring with the compound that come in the install kit. This will insure the contact is correct, and tell you if you need to add or remove shims. Watch a few ring and pinion install videos on YouTube for a better understanding.

While your at it. You have to pull both axles. You might as well replace both axle seals and bearings. You will need to rent the tools from the parts store. You will need the axle bearing tool and slide hammer. Heating the end of the axle tube slightly will make easier work of it, and the bearing and seal will come out together.

BareBonesXL

It's not too difficult but it's one of those things that if you're asking how to do it you probably shouldn't be doing it. If you get it wrong you can destroy all of the new parts plus some of the old parts.

A socal truck is worth more money staying rust-free. If it's a nice rig you might just sell it and buy a 4WD truck. That's what you really want for snow anyway. Even with an LSD, you'll have to add weight to the bed whenever it snows and traction will still be poor. Better than an open diff but nowhere near 4WD.

Plus your truck is going to start rusting away immediately in the northeast. Road salt. Immediate loss of much value.

PerryB

If you're going to do it, up the ante a bit and buy an Eaton TrueTrac differential. It's completely mechanical, no friction discs to wear out. They operate seamlessly and basically always deliver the right amount of torque to each wheel regardless of the traction available. I put one in the '05 and thinking of doing the same with my '13, ditching the ELD. It's an excellent design.

Screwed05

The Eaton is a great locker, but. At the price point it may be a little overkill. As long as the OP isn't power braking or drag racing it the clutches will last a long time.

PerryB

That's true. They're not exactly giving them away.

jp360cj

The Truetrac isn't a locker; it's a limited slip. It's definitely superior to the OEM track lock and would be my choice of limited slip. But they cost about twice you listed for the track lock. I'm not sure a 2wd street truck will benefit any from the improved torque bias and the clutches in the track lock could very well last 75K-100K miles without a lot of use.

acdii

I'll take a trutrak over a clutch based any day, even if it does cost $600. No special fluid additives needed, no skipping while turning when the clutches are new, which if installed just before winter, they will do this in snow, and make for a holy crap what was that moment if you've never had that before. Installed a new track lok in my old 99 Dually and first winter out, it did just that making a turn, acted just like my 18 does when the elock is engaged. The Trutrak does not do that. In fact I will be replacing the Elock with one this year so I wont have to remember to turn off the elock when making turns.

I put aside $1000 for my upgrade just in case, but since I don't plan to replace the ring and pinion, it may be less. I don't plan to reuse the bearings, and in fact will wrap and box the elock to put back in when the truck is sold and use the trutrak in the next truck.

Some tools needed if you are going to do it right, are calipers to measure the shims, and a dial indicator with magnetic base to measure runout and end play. Setting it up correctly eliminates gear noise, and if reusing the R&P, there will be wear in them so some re-shimming may be needed. Pinion depth should be the same, but tooth depth could be too wide and may need a few hundred to ten thousands of shims to correct. This is where the dial indicator comes into play, to measure the gap between teeth. Lock the pinion, move the ring tight to the pinion, set the indicator against the tooth, zero it, then move the ring until it touches the other tooth and get the reading. I don't have the specs right now, but if within specs, then good, if not, a shim is needed.

If doing a complete replacement another tool that is needed is a bearing puller, especially for the pinion because the shims are behind the inner bearing that is pressed against the gear end. These set the center of tooth contact on the ring. You will also need a beam type inch/lb torque wrench for setting the pinion preload. There are a lot of helpful guides out there for doing a differential overhaul, it's not easy, but if you have the time, patience and tools and can follow directions, it can be a fun project.