Attempting to upgrade NB8B diff

cobair · Postby **cobair** » Tue Jun 17, 2014 1:44 pm

I'm stuck in a dilemma, after a bit of research i've determined my 2002 ADM NB8B has possibly a 3.63 or a 3.9 open diff, i'm certain its an open diff just still sketchy on the ratio. I've heard some great things about changing over to a 4.1 LSD but since i don't know too much about diffs in general i'm stuck and what to specifically get.
Would i have to replace the whole housing or could i just replace the internals of the pumpkin?

From what i could gather, upgrading to a 4.1 open would only require replacing the crown and pinion while an LSD would require replacing the whole housing?
Or could i even get the current housing and place LSD internals in?

Most of my info was from this thread, still a solid source for anyone interested.
viewtopic.php?f=29&t=44931

One of the replies in the thread that seemed hopeful:
"If you get the entire pumpkin(Front + Rear housing) then replacing the whole lot only takes a few hours. Personally I just took the whole pumpkin out, then dropped it into a diff specialist to get a 4.1:1 crown wheel /pinion and clutch pack LSD installed on my NB8B. Was $280 if I brought in the diff or $500+ if I brought in the car itself. I think i paid $190 extra to have all the seals/bearings replaced on top at the time as well.

From memory all I did was remove the lower control arm long bolt and pop out the drive shafts. Then rear subframe brace, 3 bolts on the PPF, pry the diff off the spacer in the PPF and 2 bolts to the subframe had it. That was over 3 years ago now but it's one of the easier jobs I've done on the car."

Any advice is immensely appreciated.

Trackphotos · Postby **Trackphotos** » Tue Jun 17, 2014 1:59 pm

All 1.8 diff housings are the same, whether NA8 or NB8, open or LSD. The housings are the same, so your choices are either:
1) Replace entire diff housing if you can find a 4.1 LSD diff. Probably costly, pretty sure Plohl has a 4.1 T1 diff for sale if you want to hit him up. This is a one-person job, I did it myself a few weeks ago. You need basic sockets, couple of flat blade screwdrivers to prise the axles out, a rattle gun would be a very handy thing too. You also need a jack to lower the diff out/raise the new on in place without having to rest the weight on your ribs.
2) Replace the gears and diff centre in your existing housing. Seems like a lot of work, I wouldn't do it myself because you need to be careful to set the preload properly etc to prevent slack/tension in the gears causing wear.

At least, that's my understanding.

Postby **NitroDann** » Tue Jun 17, 2014 2:05 pm

Differentials are a set of gears that are installed inside a housing which holds the gears in alignment and the whole assembly installs into the car.

This image shows 2 complete diff conversions. You can see 2 sets of 2 axles, and 2 tailshafts, and also 2 complete diff assemblies (sometimes called pumpkins).

The diff gears are inside the pumpkins. the LSD portion of the diff is also found inside the pumpkin with the gears

You can either remove your pumpkin, open it, remove the gears inside and replace with different ratio gears, and you can swap in different kinds of LSDs or an open center.

The other option is to purchase an entire pumpkin which already has the preferred gear ratio and preferred lsd installed inside of it, then you just swap the big pumpkin section with common hand tools and no special knowledge required.

So in short, the options are to replace the entire pumpkin with one that has the right gears and LSD for your preference.
Or you can purchase the gears and the LSD you want seperately, remove the pumpkin and have a specialist swap the gears and the LSD centre into your current pumpkin.

the cheapest and easiest option is buying a pumpkin that is already set up how you want and swapping it. This means no specialist services and it leaves you with a complete pumpkin ready to bolt in, either as a spare or to sell and recuperate the cost.

Extra plug, I have a pumpkin with a 3.9 ratio torsen for sale right now, ready to bolt in.

Dann

cobair · Postby **cobair** » Tue Jun 17, 2014 2:22 pm

Brilliant! Cheers for the replies, cleared up a lot of questions, since i've got little clue about the internal gears it seems the preset pumpkin is the way to go.