Swapping diffs?
 

Gents,

I'm planning to trade my NB1 4.30 Torsen for an NA8 4.10 Torsen. We're going to make the trade in a shop and drive the cars home. What's the easiest way? Can we just keep our current axles, swap the carriers, and slip the axles back in? What else should I replace in the process?

Thanks,

The way I find the easiest is to remove any bracing, rear exhaust section, driveshaft, brake calipers, the upper knuckle bolts. Then pop out the axles diff and let the knuckle pull them away from the diff. If you have stock bushings, you might have to loose the lower knuckle bolt to get enough slack to let the knuckles turn. Then I remove the wiring loom from the PPF and unbolt the PPF from the transmission. Finally I drop the diff with PPF attached from the car. This way prevents messing with the spacer and locating sleeve on the diff while in the car.

Ooooooooooooooo. I had forgotten about the PPF. So the PPF goes to the other car along with the differential?

Thanks!

If it were me, in a shop, on a lift, I'd remove the PPF, the driveshaft, then drop the diff. As you go down, the axles will be able to come out one at a time. Once off the studs, move it left a little to pull the right axle out, then vise versa for the left.

Then again pulling the PPF is a 10 minute job for me, not a 2 day ordeal like it apparently is for most.

I find it really depends on how often the PPF has been removed and/or the environment its been exposed to. I was swapping diffs the other day and the locating "insert" on the bottom was bonded in place. Took me almost an hour to get it separate outside the car. The one I removed from my car, had it off in 10mins. I use a thin layer of anti-seeze on the locating features to make everything easier to take apart.

Replacing the axle seals and fluid wouldn't be a bad idea, nor would resealing the diff case with RTV. Replace the bushings with those fancy delrin ones if you're a baller.
Personally, I say replace the axle seals and call it a day.

I have never removed a diff. Just for clarification, there's no difference between the PPF and PPF spacers/bolts between the NA8 and NB1 assemblies...

My track car has 169k miles on it. Is there anything I should replace whilst I have the diff out of the car?

Thanks for all the inputs.

Sorry, I was distracted for a few minutes before hitting send on my last post, and didn't see yours till afterwards.

If I do it Curly's way, the axles stay in the diff, correct? I assumed I'd be replacing the fluid, and the timing is perfect for that.

There are only two upper bushings, correct?

Thanks,

No, axles will have to come out unless you swap the subframe as a whole. Yes, two bushings on the arms of the diff. Replacing them can be a bear, and it's not entirely necessary for a casually driven car.

Worth noting, you'll need to pull the axles regardless.
Either from the diff, or from the hubs.


The NA8 uses 2 piece axles, so there's a 4 bolt flange on each one near the diff that lets you remove the diff while leaving teh stubs in it, and the other end in the hubs.
The NB uses single piece axles, so you'll need to pop them out of the diff or hub.

Both have identical spline sizes at the diff and hub ends, so you can use either type of axle in either car.


Personally, i'd just drop the diff housing and pop the axles out at the diff end (easy as with a pair of pry bars, load it up and then just give it a little pop and they should pop out happily without damaging the circlip)
Removing them from the hubs is a shit of a job, since they're probably rusted in tight.




As far as replacing stuff, do the axle seals, it's easy when the diff is out.
If the front (pinion) seal is leaking, do that too.
and check the diff vents aren't clogged.




In saying all that, I'd not be going through any effort to swap from a 4.3 to a 4.1.
it's 4.88% shorter, so not really a massive difference unless it's a track car and that 4.9% is enough to just give you an edge at your track

Yeah, the bushes can be an arse.

a decent middle ground between OEM and poly is to just use void fillers, essentially a poly donut that slips into the voids of the OEM bush to give it a bit more rigidity.

That's all I'm really looking for. I'm at the rev limiter in Third gear going into Turn 4 at VIR. I've tried upshifting into Fourth and downshifting again, but it's not any faster. I'm near the rev limiter coming out of The Snake (Turn 6) in Third gear, and at the ends of the long straights in Fifth. All I want is a couple hundred rpms back, without having to drastically change how I drive the car.

Why?

Thanks,

They can just be hard to push out/in since they're large and part of a big awkward assembly that often won't fit in the vice.

If you're lucky enough to own a press it's a lot easier.

I spent some time under the car today... I think I get it now. Thanks, Curly.

Just one more question. The PPF basically holds the diff in position, but once the PPF is removed, the rear is only held in place by those four nuts (two on each side) attached to the plate that holds the bushings we've discussed, correct?

Thanks,

There's also a 17mm bolt on each arm. Let's see if I attach a photo correctly...
https://cimg5.ibsrv.net/gimg/www.mia...dda169a51e.png

My '99 does not have those 17mm bolts. I was sure, but I checked anyway. Jeez, if I had missed those, I would give up any further mechanicking...

Huh...interesting. I pulled a torsen out of a 99 to put in my 92 and the mounting system is the same. Someone with more experience will likely chime in and school me on which models are different?

Pics?

You may need to find an optometrist.