No more speedo signal from new diff

[Wanganstyle]

hey-

just spent some time reading this-

if the e28 diff bolted to a e30 rear diff cover plate and into your car, the speedo ring SHOULD work proper.

E28's should have compatible speedo ring teeth with e30- I will see if I can find otherwise looking through my stash - v few e28 parts in my collection so I will try my best-


there are 2 common 188mm speedo gear patterns; one is larger diameter than the other. BOTH are compatible with same car, same speedo sensor etc-

my 1998 e36m had a larger speedo ring originally with factory 3.38 gearing+clutch lsd; to fit 188mm 4.10 ratio + torsen from Z3 in same 188mm diff case I had to swap to the smaller speedo ring; I used original speedo sensor from my e36M with the different speedo ring - then went for a V-max run. Speed sensor worked 100%

[nando]

they're all 9 tooth wheels, some do have different diameters though.

[Wanganstyle]

they're all 9 tooth wheels, some do have different diameters though.

thats what i thought-

I have distinctively used the same speedo sensor sucessfully with both size speedo rings in the same diff housing and same car.

[328ijunkie]

Even more interesting lol.... Thanks for your 2 cents man!

[rammstein]

OK... I fricken give up with this. I hooked up my multimeter and attempted a continuity test, and it just beeps the entire time (short). I have the sensor out, and I can even hold it up to the old diff and run the blades from the old diff through it, but its not gonna matter until I figure out the proper way to do this test. I also saw some metal flakes on the sensor where the magnets are, which is disconcerting. The diff is super loud, but I've up till now assumed that the loudness is from the urethane diff mount. I still hope it is from that, and god willing if I ever get this shit to work I'll try changing to mount back to rubber to hopefully quiet it the hell down.

If anybody can help me figure this out you've got a nice glass of scotch waiting for you in Miami.

Insert picture of angry, crying man.

[rammstein]

UPdate- ok, I messed with the sensor some more, and I got it to work manually with the OLD diff by putting the blade pretty far in. Thus, I think the problem lies in the distance from the sensor to the blades in the new diff (continuity test does not work on the diff in the car). So I need to come up with a way to get it to stick in farther, or sell the diff and get an E30 diff.

[rammstein]

By my estimation, I need the sensor to be in about 2-3mm further for this to work. I have no idea how to make this happen.

[daleb]

Ron Stygar, BMW guru, researched and wrote up a lot about these senders as part of swapping a 3.46 diff into his Z3 M Coupe back in 2001.
This writeup is mainly about the diff swap, but has a lot of information about different speed sensors installed in the medium case ( 188 ) BMW diff.

http://www.bimmerfest.com/forums/showthread.php?t=5078

In case you don't know, the Z3 6cyl diff is a direct bolt in swap the diff in E30s with 6cyl and E30 M3. (except maybe the axle stubs, 10 second swap, BFD)
E30s do have an early and late style speed sending unit, difference is the electrical connector, my 87 325 has the early style, my 90 325i has the late style, assuming the 88 body change is the cutover date.

[rammstein]

Daleb- that link was singlehandedly the best resource I have seen on this. You are definitely the prize winner.

So... I got out the dremel and ground down the sensor as shown in the link. I had one issue where the long part of the sensor actually came apart from the rest of it (the plastic is sort of molded one piece over the other, and I ground too much around that part). So after trying three different adhesives, I got that taken care of. I had to grind it down a LOT. I now have what I believe will be a working setup, except I have no way of bolting the sensor into the coverplate now that it is ground down. The link shows how somebody machined a new bolt-down plate. I don't have the facilities to do this, so I still need to think.

Let this thread serve as a warning to anyone who thinks you can just take a 5 series diff and bolt it onto a 3-series. DON'T DO IT. IT IS NOT WORTH THIS BULLSHIT. People told me this would work no problem, but my experience is proving otherwise.

[rammstein]

OK... I think I came up with a solution. I am going to order 4 more brackets and stack them up to make one bigger one. I know for those of you with the ability to machine things this sounds insane, but its all I can come up with.

[daleb]

rammstein:
What year is your E30? What ratio is the E28 diff you installed?

there are a bunch of variables to this, which sensor do you have (part number), how deep is your cover, some stick out more then others, liked the finned one from the M Z3 Coupe, what diameter selector ring do you have?

If you read down far enough in Ron's thread, you'd see this image, which shows 2 similar looking speed sensors, that have a different trigger point.
You may be able to install the 2nd one that triggers further out if that is not the style you have already.

[rammstein]

Well, I finally got it working. I actually already had gotten it to the point where the multimeter was showing that the sensor was getting a read, but then I had no way of bolting it down like I said. Then I ordered 4 plates, figuring I would just cut them a bit, but then I got really frustrated and started looking around my house. I found a pile of metal shims that came with my lift that weren't needed, and so I just spent 2 hours cutting/filing them to fit. I just got back from a test drive and I now have speed reading. Tomorrow when I get home from work I'm gonna put it up again to check for leaks. What a freakin day. Regardless, drinks are on me Daleb- that link pretty much saved my ass. I'll give a final update tomorrow after I give it a once over.

[Wanganstyle]

any update? can you post some photos?

you could update to the e36 sensor that has one long blade and the plug as well, as it is only a magnet -

the e36 188mm diff cases like the small spiders.