Toasted Diff

[bimmerboi318]

This is kind of a follow up on the last discussion I had where I assumed my rear u-joint was worn and I needed a driveshaft. Well...my assumption was wrong. The knocking noise that was coming from the rear of my car got significantly louder over the past few days and seemed to catch or bind up every now and then. I put it on a lift in 3rd gear running and I could easily hear that the sounds were coming from the diff. Rats...Today I pulled the cover and saw that the pin thingy (very technical I know) that the planetary gears turn on had slid out and was hitting the pinion gear every time the diff rotated. It has slid out about a total of 1/16" or so. Needless to say there is damage that would make rebuilding it too expensive to be practical. The pinion has some nice chunks out of it, that pin is ruined, the carrier is probably worn from the pin moving around, the bearings are all probably shot from having so much metal floating around, which leaves me with a very nice diff case and not much else. Back to driving the Nissan hardbody for now...

I plan on buying a diff off ebay or something used. I was thinking a 3.91 LSD. My big question is, will this throw off my speedo or anything, because I know there is a speed sensor on the diff itself with its own tone wheel. But I do not know if this is dedicated to the abs or if it also supplies the speedo signal. Thanks.

[1996 328ti]

Be sure to get the correct size diff. Not all diffs will fit.
You need one made for a 4 cylinder.

I don't think changing the diff will throw the speedo off but your speed will be different at the same RPM as previous. I never remember f it will be higher or lower.

[Jared]

A good place to get a diff is here... http://www.cherry-auto.com/
I've bought from them before, and got exactly what I wanted.

Buying another diff and putting it in will NOT screw up your speedometer, even though the speedo does in fact use that sensor in your diff.

[Jared]

Oh, and if your current diff is lower than 3.91, adding a 3.91 will make each gear shorter, meaning at highway speeds the engine will be turning faster to go 70 than it used to.

[mrnine]

RPM Calculator

http://www.368s.com/tools_rpm.phtml?PHPSESSID=5af159a2085f1fcb93f620dfc2944bf3

[Jeff Spooner]

The speedo reading is taken off the left rear wheel speed sensor not the diff

[bimmerboi318]

The speedo reading is taken off the left rear wheel speed sensor not the diff


Mine is a '95 and only has 3 channel abs. It doesnt have speed sensors on the rear wheels, only one on the diff. I believe later ones had sensors on all 4 wheels. I was just curious if it had a sensor on the trans output shaft as well, but I dont think it does. I guess as long as there are the same number off teeth on the tone ring, the speedo will be accurate.

[motorsport]

i found good aftermarket parts for cheep here www.thepartsbin.com

[Jared]

Mine is a '95 and only has 3 channel abs. It doesnt have speed sensors on the rear wheels, only one on the diff.


Same here.

[KIRASIR]

Not on our cars. Unplug your differential sensor and see if your speedo is working? ;)


The speedo reading is taken off the left rear wheel speed sensor not the diff

[Jared]

Actually, my 96 M3 w/ 4 channel abs got its speed reading from the diff as well! Jeff, what are you driving?

[Jeff Spooner]

OK, OK I have been working on to many 740 BMW's latley. it is in the diff. I do know where there is two brand new 4cyl lSD diffs if any one is intrested.

[bimmerboi318]

That's ok Jeff, I appreciate the help and know you're a good source for info seeing as you're one of the few (if not ONLY) BMW techs on the board.

So, speedo should remain accurate.

BTW how much do one of those lsd's you weren mentioning cost? I'm kinda leaning towards a used one off of ebay in the range of 200-300 bucks...but maybe if the price is right it might be worth it. Thanks.

[Jeff Spooner]

I think they want $750 each. they sell for around $1200 new. call me if you want more info tomorrow 803-551-1070

[J!m]

I have the original diff from from my ti. Let me know if you are interested.

[bimmerboi318]

Are the larger output flanges the only reason an e30 6 cylinder diff is different? And if that is so, will a 4 cylinder e30 diff fit with NO modifications? Otherwise, I'll have to get the e30 cv shafts. Thanks.

[1996 328ti]

I think the main difference in a 6 cylinder diff has a larger housing. Better dissipation of heat. Not sure if an E30 4 cylinder diff will bolt right up. It might need different flanges.

http://www.318ti.org/notebook/diff_conversion/index.html

[ClubSport332ti]

Speed is taken from the Diff! The ABS is in he axel. You can get any e30 diff to fit the ti ( the best option is to get an e30 diff from a member and then get the half shafts and do it that way.)

[bimmerboi318]

Speed is taken from the Diff! The ABS is in he axel. You can get any e30 diff to fit the ti ( the best option is to get an e30 diff from a member and then get the half shafts and do it that way.)

ABS is on the axles on cars with ASC+T, and they also have 4 wheel independant (4 channel) abs. Mine however has no speed sensors on the axles. Only the center diff sensor.

I just bought a 3.73 lsd so I'll find out first hand how easy the swap is. Thanks for the help guys.

[Constant]

ABS is on the axles on cars with ASC+T, and they also have 4 wheel independant (4 channel) abs. Mine however has no speed sensors on the axles. Only the center diff sensor.

You sure about that? #11 is the ABS wheel speed sensor, found on the '95 318ti. It uses an inductive pickup where the toothed pulse ring at the end of the axle inserts into the hub. My '96 without ASC definitely has the ABS sensors in both rear trailing arm hubs.

http://rust.mine.nu/bmw/images/r/1547.png

[bimmerboi318]

I'm pretty sure. I've had the rear end torn down a couple times and haven't seen any speed sensors. The only thing even slightly resembling a sensor is the pad wear sensor.

[Constant]

Although it is possible your car has an unusual factory setup (it's happened before), I don't think it would make sense for BMW to make a different ABS system on the '95 ti. IIRC, all the other E36s without ASC+T are 3-channel, 4-sensor systems. The rear 2 sensors are tied to one channel. If either rear sensor detects slippage, both rear brakes will be pulsed. Note that 3-channel does not refer to the number of sensors, but rather the number of hydraulic controls that can modulate the ABS.

Interestingly enough, even on ASC+T equipped 318ti's the ABS works as a 3-channel setup. The 4 channels on ASC+T cars allows the rear brakes to modulate independently during traction control. Yet when ABS is activated, both rear brakes are modulated in unison. Thus a pseudo 3-channel operation.

Constant

[bimmerboi318]

Just received my E30 3.73 LSD in the mail today :twisted: I'm getting tired of driving my nissan hardbody...

Constant, is there a particular reason that the e30 axles wouldnt directly fit? Or was it simply because of the tone ring that you used the ti axles with outboard 6 cylinder CV joints?

I am assuming that you are the same Constant that wrote the very nice and informative differential swap how-to ;}

[Constant]

Constant, is there a particular reason that the e30 axles wouldnt directly fit? Or was it simply because of the tone ring that you used the ti axles with outboard 6 cylinder CV joints?

Yes, the E30 axles will directly fit. I just happened to swap mine because the pulse ring on the E30 axles I bought were in terrible shape.

Just an FYI, if you use the unmodified E30 axles, take caution with the ABS sensor. I didn't have a problem, but some people said their ABS sensors actually hit the E30 pulse ring. You might have to put a spacer on the sensor.

Constant

[bimmerboi318]

*ahem*

A public service announcement. Constant, I would like to take this opportunity to say that I was, in fact, wrong about not having outboard speed sensors on my axles. I took them out, and there they were staring at me. I owe a round of drinks :dribble: Although I was looking and I dont think there is a way for the car to brake individually in the rear, since there's only one brake line going back there. Again, I could be wrong here :rolleyes: :

I also underestimated how pricey axles were going to be. 140 bucks each for new aftermarket. 79 for remans. I found a place that supplies dealers that has them for 35 each, but I need an exact exchange...they wont let me pay a core charge. So, it's looking like the 79 dollar remans.

[bimmerboi318]

Well, after a long time of not having a working computer, i've finally made it back to the forum. I'd just like to say that the 3.73 upgrade was very worthwhile and is indeed the poor man's supercharger. The swap was pretty straightforward. The only thing I noticed was that the vent tube and left side top bolt for the cover hit the unibody. Some "adjusting" of the unibody was needed for clearance. Best 150 bucks I've ever spent. Well...on my car at least... ;}