Keep old differential?

[Reasoned1]

Hi, folks.

I'm planning on replacing the OE rear differential on my 2004 ZHP with limited slip. I'm leaning toward MFactory, but very attracted to WaveTrac, and Quaife is still in the running. I'm willing to buy now, but my car is in storage, so I won't be able to get it to the shop to do the swap until Spring (I do some work myself--shocks, springs, accessory equipment, etc.--but want somebody with experience doing the diff). Unfortunately though, the vendors want the old diff back in 30 days, so here's my question: Is there any reason to keep my old differential and forego the $400-$500 core charge? I'm thinking I might want it in the event of a problem or, if hell freezes over, I might decide to sell to a buyer wanting the original equipment. Please advise...

[NoVAphotog]

Hi, folks.

I'm planning on replacing the OE rear differential on my 2004 ZHP with limited slip. I'm leaning toward MFactory, but very attracted to WaveTrac, and Quaife is still in the running. I'm willing to buy now, but my car is in storage, so I won't be able to get it to the shop to do the swap until Spring (I do some work myself--shocks, springs, accessory equipment, etc.--but want somebody with experience doing the diff). Unfortunately though, the vendors want the old diff back in 30 days, so here's my question: Is there any reason to keep my old differential and forego the $400-$500 core charge? I'm thinking I might want it in the event of a problem or, if hell freezes over, I might decide to sell to a buyer wanting the original equipment. Please advise...

I bought a 3.46 core off of E46fanatics and had the seller ship it to Mfactory. Avoided any core charge and down time for the car. Since your car is in storage you have time to shop around for a core that someone else is selling and use that and then just keep your old diff when the new one arrives like I did. I highly recommend upgrading the gearing to 3.38/46 unless you commute on the highway or go on a LOT of road trips. And even then it's not that big of a deal for the added punchiness around town.

[Reasoned1]

3.46 is what I was thinking since the car is for thrills not long hauls. :)

I would love to hear more about your upgrade. I'm in central Vermont, so not alot of BMW shops around, but I have a great garage I go to and they're all for attempting the swap. Shouldn't be a big deal, right? Pull the old one off the axles and drive shaft and slap the new one in, right? Please tell me it's that easy... My 2004 xi has 3.46 (among a few other things), and it feels punchier lower down but, of course, it peters out higher up whereas the ZHP just keeps building.

Just noticed you're in Arlington, VA--my son lives in Arlington, and he facilitated the purchase of my ZHP at Avazi Auto Group in Gaithersburg, MD.

[slater]

3.46 is great, and LSD is awesome in the winter - really, a safer option too. more grip, is, well, more grip! :)

where in central VT? i grew up in rochester (right on rt 100).

[wertyu78]

You might want to also consider Diffsonline. Yes, they aren't the most affordable option, but arguably, they are the best. Hands down the best mod I've done to the car, and Diffsonline made it painless. I had gone through two OS Gikens (both exploded) before going going with my Diffsonline unit.

[Sockethead]

3.46 is what I was thinking since the car is for thrills not long hauls. :)

I would love to hear more about your upgrade. I'm in central Vermont, so not alot of BMW shops around, but I have a great garage I go to and they're all for attempting the swap. Shouldn't be a big deal, right? Pull the old one off the axles and drive shaft and slap the new one in, right? Please tell me it's that easy... My 2004 xi has 3.46 (among a few other things), and it feels punchier lower down but, of course, it peters out higher up whereas the ZHP just keeps building.

Just noticed you're in Arlington, VA--my son lives in Arlington, and he facilitated the purchase of my ZHP at Avazi Auto Group in Gaithersburg, MD.

Yes it is that easy. I can do it in two hours start to finish laying on my garage floor. There are a few tricks to it but any good mechanic will be able to figure it out. I would have the mechanic check the rear differential bushing while they are in there. The rubber has a habit of splitting/cracking. Sometimes you can see it without removing the diff if it's bad enough but sometimes you can only see/test it with the diff out like we did with Daniel's car.
If your car is for thrills, then definitely go for the 3.46. There are only two performance upgrades that give you a real performance increase without going into the engine internals: Differential gearing change and forced induction.
Daniel gives good advise about getting a donor diff. I think that may be your best bet in your situation. You can always sell your original diff if you don't want it laying aound.

[Reasoned1]

I'm in Barre, and there are some very nice roads to tool around on up here--including Route 100 (to be avoided during peak traffic hours--especially during leaf-peeping season).

I fantasize about getting a supercharger, but it'd be REALLY hard for me to justify the expense, and it seems to me that going that route is opening a can of worms for minimal performance impact at low RPM--hardly worth it when I have as much fun as I do already with the car. Plus, I can do A LOT of maintenance and mods with the money it'd take to install a supercharger.

Diffsonline has an unbeatable reputation, but I am mighty attracted to that MFactory diff for $1,800 (including $500 core charge).

On further thought, why don't I just pull my existing diff, and send that to MFactory, since I'm not driving the car for a while? I might even get the cojones to put the rebuilt one back in...

Just watched the DIY for this by "TH"... It actually looks pretty straight forward--barring any broken or stripped screws.

[MFactory]

If your car is in storage for Winter, then best bet is to send us your core in advance and we can rebuild it for you.

It only takes us a couple of days to rebuild and ship it back out to you :)

[az3579]

Honestly, a factory diff isn't worth the core charge, so you might as well send in your old one.
If you really need to, I'm sure you can source a stock open diff from a junk car for peanuts.

[slater]

I'm in Barre, and there are some very nice roads to tool around on up here--including Route 100 (to be avoided during peak traffic hours--especially during leaf-peeping season).

I fantasize about getting a supercharger, but it'd be REALLY hard for me to justify the expense, and it seems to me that going that route is opening a can of worms for minimal performance impact at low RPM--hardly worth it when I have as much fun as I do already with the car. Plus, I can do A LOT of maintenance and mods with the money it'd take to install a supercharger.

Diffsonline has an unbeatable reputation, but I am mighty attracted to that MFactory diff for $1,800 (including $500 core charge).

On further thought, why don't I just pull my existing diff, and send that to MFactory, since I'm not driving the car for a while? I might even get the cojones to put the rebuilt one back in...

Just watched the DIY for this by "TH"... It actually looks pretty straight forward--barring any broken or stripped screws.

barre - awesome. yep, lots of good roads near there.

i agree about the supercharger. the power is tempting, but it is a LOT of money that could be spent elsewhere (like an LSD, which i personally feel is a better investment).

are you up for pulling the diff yourself? just because it would have to sit at your mechanics' place until you got the new diff back. like rob said, it's a pretty easy job.

[NoVAphotog]

3.46 is what I was thinking since the car is for thrills not long hauls. :)

I would love to hear more about your upgrade.

Just noticed you're in Arlington, VA--my son lives in Arlington, and he facilitated the purchase of my ZHP at Avazi Auto Group in Gaithersburg, MD.

It definitely has been a good upgrade. Slater was right when he talks about it making a difference in the winter. That is where I REALLY noticed it. I have only driven this car through two of them and our Virginia winters aren't really that bad. We got our fair share of the white stuff. The first I had Blizzaks and the open stock diff. Car handled great but I found the car pulling in one direction a lot of times which was annoying. Second I had the Blizzaks again with the LSD, not only was it more fun, but I noticed that when pulling away or if I got stuck, having BOTH wheels pushing me forward made it a LOT easier to control. I drove around in DC the day after our big blizzard and despite plowing a few streets with my front bumper had ZERO problems.

That said, I have recommended the 3.46 as an upgrade even without the LSD unit for people on a budget. The unit is nice to have but realistically, I noticed more of a day-to-day impact from that change. I drove a stock ZHP at the Reunion and couldn't wait to get back into mine driving around the twisties in Tennessee. I missed the punch immediately. 2nd and 3rd shifts are RIGHT in the powerband and having all the pull you need in 6th on the highway is a great feeling. MPG wise it was a non-issue. All the way to TN and back I averaged 29ish while sitting a little over 3k at 80. Again, this is why you have pull in 6th which balances it out.

All in all, I agree with Rob, it's a very worthwhile upgrade that you WILL notice if you up the gear ratio. I cannot say that you would notice it as much with the 3.07 as our cars really just don't have the power to "need" the LSD. Obviously, the power of the engine doesn't change with the gearing but it allows you a little bit better "access" to it.

Oh, and Arlington is great. I love being able to walk to work! Though I do miss driving my ZHP as much...though it does give me a "bonus M3" feeling in comparison when I go from the 4runner to her or not driving for awhile.

Avazi Auto group gets some nice cars in from time to time. Do they match them with good service?

[slater]

I cannot say that you would notice it as much with the 3.07 as our cars really just don't have the power to "need" the LSD.

dude, you're just not driving it hard enough. ;) even my 325iT w/ 3.46 needs an LSD... ;)

[holyc0w]

We got our fair share of the white stuff. The first I had Blizzaks and the open stock diff. Car handled great but I found the car pulling in one direction a lot of times which was annoying.

I drove through a mild storm recently and the car did get a bit squirrely, especially when moving from a stop.

[Reasoned1]

Thanks for all the advice and reassurance, guys. The plan is to pull the differential myself (looks easier than the springs and struts I did last winter--what a BITCH!), send it in for rebuild, and reinstall it when I get it back. Will I get my original pumpkin back? I'd like to since there're so few miles on it.

As for Avazi, they were GREAT--very communicative, easy to deal with, and eager to make everything right. Most importantly, the car they sold me is SOLID.

I don't drive either of my BMWs in the winter yet (doubt I ever will with the ZHP)--I have an '01 LeSabre (ha-ha) and an '05 Durango for bad and really bad conditions, respectively. Traction control has rudely interrupted my driving several times with the ZHP (never with my xi)--hence, my desire for an LSD.

[Sockethead]

If you get stuck doing the diff swap, feel free to shot me a PM. I've done the swap about 4 or 5 times...
Unfortunately, Traction control is vey intrusive on these cars. I still find it annoying even with LSD. You can turn it off with the button or do some reprogramming if you have the skills or feel brave.

[Reasoned1]

Quick update... I swapped a used, open, 3.38 diff into my ZHP earlier this season (did it myself which wasn’t too bad—getting up and down from under the car was tiresome), and LOVE IT! Tomorrow, in fact, I’m taking advantage of MFactory’s 20% off sale and ordering myself a 3.46 LSD (I was talked out of going shorter) and do it right.

[ELCID86]

^ Good call. I think you’ll really like it. ;-)

[Reasoned1]

Order placed—got a 3.64 which was the only non-3.07 they had on hand. CANNOT WAIT TO DRIVE IT! Unfortunately, it’ll be several months now...

[ELCID86]

Glad you got the one you really wanted Bill.


---
"ZHP is a garbage option anyway- just some cosmetic upgrades with a different cam and diff to claw back some of the performance lost fitting those hideous and heavy wheels. Any 330 with a 3.46 diff will smoke a ZHP every time. The whole Mafia thing reeks of childish behavior." - anonymous E46 fanatic

[Reasoned1]

Well, I wanted the 3.46 which you recommended and I knew would be at least as delightful as our 3.38's, so I'm a little nervous it's going to be too aggressive, but I don't drive it much on interstate and love torque, so I'm excited about that and am a little relieved knowing I can't find myself guilty of not going short enough. Also, I conservatively ran the numbers a bunch of different ways and keep finding it ought to suit my driving style perfectly (picturing passing on State highways in 3rd, between 50 and 80, like it's nothing), still cruise at 80mph at only 3,400rpm (which is a tad much for long trips, but I never do that in this car) and still get me to 160 should the need arise. ; ) Finally, if anything can keep me from investing in FI, it would be this. The weather report shows two weeks of fair weather coming so, if I take delivery this week and install it next weekend, I may yet be able to give you a road report this season and put all my theorizing to rest (my head hurts).

[Phillips0417]

Reasoned, did you ever swap this LSD in? What are your thoughts? I have a 3.07 Performance Gearing LSD in my car and have considered going to a 3.46 for my twin screw 3 car.

[Reasoned1]

I did, I did... it doesn't factor into my driving much but, even with the DSC on, it doesn't kick on nearly as much, I'm better able to control the traction myself at launch, and when it does flash on, it doesn't seem to kill the power like it did--as if it's only warning me it's thinking about engaging. I leave the DSC on, as a result, and it's made my driving experience MUCH more fun! Furthermore, I was worried I'd wind up with some clunking, which is common I gather, but it's smooth as silk, so I am one happy camper with my MFactory 3.38 helical LSD.

By the way, I now I have two spare open diffs on the shelf (a 3.07 and a 3.38). I'm thinking I might find a nice, higher mileage 330i for my next DD that would benefit nicely from the 3.38.

As for your twin screw situation, I'm not qualified to offer an opinion, but I've read multiple reports online that say the 3.07 is ideal for superchargers (I would bet even more so for a twin screw with extra low-end torque).

[Sockethead]

I'm running a 3.15 with a twin screw... pretty much perfect. I wouldn't go much higher than a 3.38 with FI. My wife was running a 3.08 in her highly modified 135 and she was running in the 12s at the local drag strip... and that was pretty much spinning in 1st gear

[Newjack]

I'm running a 3.15 with a twin screw... pretty much perfect. I wouldn't go much higher than a 3.38 with FI. My wife was running a 3.08 in her highly modified 135 and she was running in the 12s at the local drag strip... and that was pretty much spinning in 1st gearIs 3.08 is still stock gearing on the 135 diff?

Sent from my Nexus 5X using Tapatalk

[Sockethead]

Yes, that is the stock ratio. On the newer BMWs, the ring gear is welded to the differential unit. She to took the car to VAC Motorsports. They cut off the ring gear and re-machine all the parts for bolts then installed the LSD unit. I didn't touch that one :)