Rear diff: rebuild or replace third member?

[lmelmed]

Third member (3.50 with 28/traction look) is making a lot of noise. Let's assume the pinion gears are done.

I don't feel comfortable tackling a rebuild. What should I expect from a shop (big city, high labor rates)?

I might feel comfortable dropping in a whole new third member. Looks like those are around 800-900 completely rebuilt.

So you can see my question: if it is going to cost almost as much to rebuild the one I have (100 an hour shop rates) am I better off just doing a new third member?

 

[DirtDonk]

Would you be doing a standard rebuild using your existing limited-slip unit? Or would you be wanting to upgrade/update to a different type, such as a Truetrac or similar?

Gears can run from $100 to $350, while a master parts kit is usually in the $100 to $150 range.
Traction devices can run from $100 used, to $600 (or more for a selectable type like ARB and Zip Lockers) or so.

Labor? I think it's going to vary by shop even within your own area. It certainly does around here.

Buying a new, already set up 3rd member might have two advantages.
First is that there is virtually no down time.
Second is that, once you're done, you will have something to sell on to recoup just a little of your cost. And at that point, if you want to mess with it first to see what these things are all about without the stress of wondering if you'll mess up a critical component, then by all means mess about with it.
If you fix the noise, it's worth even more because to someone, it's still a usable unit for them until they get the one they want.

Paul

 

[lmelmed]

That is very helpful. It is just street driven with kids. Truthfully, I don't even need limited slip for my driving, but it came with it so I figure I will want to keep it true to how it came from factory.

I had not thought about ability to learn on the old diff or just sell it and recoup. Good suggestions.

Am I correct that swapping the third is relatively straightforward? New wheel bearings and drive shaft (was trying to eliminate noises), so expect those steps to go ok. Other than the difficulty of lifting it in, anything else I should be concerned about?

 

[DirtDonk]

New wheel bearings is a distinct bonus! Glad you replaced those already.
Yes, it's pretty straightforward. Two of the three steps you're already familiar with.

1. Remove or at least pull the axles slightly out.
2. Remove the driveshaft.
3. Remove all the nuts and yank the "chunk" or 3rd member.

Some people do it with a jack, and that makes a lot of sense, but I just sit cross-legged under there and pull it into my lap, then roll out from underneath. It's heavy and awkward, but pretty straightforward.

Paul

 

[DirtDonk]

Hmm, if really on a budget, you could actually just leave the existing limited-slip alone and simply have someone replace the gears and bearings. If you're not needing the device, and it's likely the clutches are pretty worn out by now anyway, it's not really critical to do that step and you could have it all done on the cheap.
This works well too, if you're not daily-driving the rig and don't mind if it's down for a weekend or two.
Oh, and you do save a ton by not having the shop to the teardown on the vehicle. If you just walk in with the differential assembly in hand, it's a much lower labor rate obviously.

If budget is important, but not a deal-breaker, then I would at least refurb the limited-slip too while you were in there. No sense in doing all that work and only doing it half way I say.
And they're actually pretty easy and inexpensive to set up. You can even buy a new one for a few hundred dollars, and a used one for just a few. Some new clutches and springs, and an inspection of the case for any damage, and you're on your way.
A few ways to tackle this.

Oh. And of course, adding the old Bronco "snowball effect" to the mix, now is actually THE BEST time to upgrade to 31 spline axles at the same time!
The cost of the diff itself does not change for 28, 31 or even 35 spline models most of the time. You only have to factor in the cost of new axles and bearings ($250 for the pair, with bearings installed from us at least) and no extra labor to install them.

It sounds like you don't need this option. But you should at least know about it.

Paul

 

[lmelmed]

Wish I had done new axles when doing the bearings! Thanks again for advice.

 

[DirtDonk]

Yeah, was knowing that would be a sticking point as I was writing that. But at least you can still sell 28 spline axles with new bearings for a good price.
I'd say to the right person they'd be worth $100 bucks so they don't have to go through it on theirs, or don't have to change the diff to upgrade to 31's or whatever reason.

Got a buddy riding on my old 28's right now in fact. Beautiful Bronco but he just hasn't decided which way to go on the axles and diff yet. I think he was waiting to decide what gear ratio with the new setup, but as we like to say 'round here... "It's only temporary. Unless it works..."

Paul

 

[Miker]

You need to consider PM'ing Delconick (Nick) on here. Heck, he has a shelf full of them rebuilt in all sorts of gear configurations. He certainly knows how to set them up as well. I, and others have just gotten whole center sections from him as ready bolt ons. Not crazy expensive either.

Just saw you are in Bethesda. If that's MD., you could drive to see Nick's shop (actually a warehouse) bring your center section, he might give a core credit. Bring extra coin, you'll be like a kid in a candy store........

 

[bcmbcmbcm]

I'm facing the same dilemma. I have 31 spline axles ready to go in. Working on new brake assemblies too. Leaning towards a true trac. I have ordered up a Lentech AOD with the wide ratio gearset so I was leaning towards running the 3.50s and not touching my front D44. I really want a truetrac. I also am going to be changing housings. I have someone local who will give me a great deal for rebuilding an axle as a 'bench job' meaning I bring it to him as an assembly instead of towing in the EB. But at this point, new axles, new housing, new diff, I am 90% of the way to a whole new 9". The only parts I would re-use would be the bare chunk housing and the R&P.

Any thoughts on what a drum to drum 3.50 9" is worth in good serviceable shape? Decisions decisions decisions....snowball effect for sure!

 

[MitchE]

Over 5 years later. I have the same decision. Not sure you'll ever read this but wanted to say thanks.
Love this site.

 

[SteveL]

That's a pretty common diff. Check craigslist.com or the local hot rod swap meet. You should be able to find a decent used one for $200-300 and just swap it

 

[Rustytruck]

the factory limited slips are prone to breakage and stripping the splines on the drivers side axle. so for me I would pull the center section and check the splines on the axle and the ring gear bolts on the traclok and see if it is cracked around the bolt holes. pulling the axles and center section is not worthy of paying someone 100 per hour to do as it takes no professional talent. once you see what is going on then you can take the center section to be fixed or swapped. if you must keep the traclok then buy a billet steel hat for it on Ebay worth every penny. if you pay a professional to rebuild the center section make sure the pro puts in a solid spacer for the pinion bearings up grading for the crush sleeve. there is an upgrade price for this worth every penny.