e30 Diff Swap [Archive] - 318ti.org forum

andy

03-01-2006, 10:19 AM

Well, I picked up an e30 325is diff today, although I can't really get started until the engine's done. Here's the first pic:

http://www.318ti.org/gallery/showgallery.php?cat=600

First things I'm seeing here:

1. The output shafts' flanges' holes are indeed further apart than the stock unit. I assume this is where swapping flanges comes in.

2. The input shaft is about 1 cm longer than the 'ti unit as measured to the front mounts. This is not good, I really didn't want to worry about the driveshaft not fitting.

3. The distance across the diff from output shaft to output shaft is about 3 cm longer. This jives with the e30 halfshafts being shorter; I've seen some botched jobs before where the wrong lengths of halfshaft were used and all kinds of problems happened.

I think I'll start by looking at the e30 halfshaft distance and see if that makes up for the difference; that would make this easier. I'm still a little worried about #2 above, however. Hmm...

L84THSKY

03-01-2006, 07:03 PM

Andy

I've been waiting for more info on this dilemma for awhile. I have an E30 diff to put in too. Here is my question. What is the flange to flange width of the E30 diff with 318ti flanges, and what is the flange to flange width of the 318ti diff with 318ti flanges?

I plan on putting in the E30 diff with 318ti flanges, and wanna know how much extra width, if any , there will be.

That issue with the drive shaft concerns me. I haven't heard anyone complain about that being an issue.

Eric

Well, I picked up an e30 325is diff today, although I can't really get started until the engine's done. Here's the first pic:

http://www.318ti.org/gallery/showgallery.php?cat=600

First things I'm seeing here:

1. The output shafts' flanges' holes are indeed further apart than the stock unit. I assume this is where swapping flanges comes in.

2. The input shaft is about 1 cm longer than the 'ti unit as measured to the front mounts. This is not good, I really didn't want to worry about the driveshaft not fitting.

3. The distance across the diff from output shaft to output shaft is about 3 cm longer. This jives with the e30 halfshafts being shorter; I've seen some botched jobs before where the wrong lengths of halfshaft were used and all kinds of problems happened.

I think I'll start by looking at the e30 halfshaft distance and see if that makes up for the difference; that would make this easier. I'm still a little worried about #2 above, however. Hmm...

cali-ti

03-01-2006, 10:10 PM

notice the ti diff cover extends further back? you'll likely need to "make" a little room in the rear subfloor beam to clear the top of the diff cover, but other than that, it's no problem.

i believe the ti flanges extend out less than the e30 flanges, which is why the swap of flanges and using the ti halfshafts appears to work. that said, i swapped to e30 flanges and halfshafts. i'd be interested to hear if the person was able to swap in the m-coupe halfshafts with no issues. never did hear ...

CaliDohBoy

03-01-2006, 10:16 PM

What is the total benefit of doing this? I'm not too savvy on LSD's and ratio's and all that

cali-ti

03-01-2006, 10:34 PM

higher ration (3.45 -> 3.73) results in quicker acceleration (and a 10% increase in revs turned at the same speed).

typical benefit is getting limited slip as almost all the ti's came with open diffs. the e30 diff can also handle more power (large case diff coming from a e30 325).

CaliDohBoy

03-01-2006, 10:43 PM

cali-ti

03-01-2006, 10:54 PM

the only TRUE easy, direct bolt-on, no issues LSD is the 3.45 LSD from the 95 (and i believe early 96) ti's that had it or, it appears, m42/44 z3's that again might have had it. it was even an option for automatics, but that gives a higher ratio, 4.44.

andyman7931

03-01-2006, 11:08 PM

hmmm... thinking... hmmm... I have a 3.73 LSD from an e28 (same as e30 except for rear cover) sitting in my garage, how is drivability with that gear ratio in our cars?

tengohambre

03-02-2006, 01:14 AM

so, if my '97 (most likely) has the open diff, I would benefit from getting a LSD for my car which would be an easy bolt on direct replacement and a good mod? Hmmmm... I may have to find one of these "LSD"'s you speak of... :evil_lau:

Easy? I have an e30 lsd, while using my ti halfshafts and flanges. Getting the old diff out was a pain in the @$$ because those freaking top bolts are hard to access and were covered in 10 years of dirt. Also, make sure you have that torx socket!!! Sure you can use a hex socket, but you'll probably end up rounding off some of the bolts like I did. Also, since the diff is bigger, I had to pound in some of the metal so it would sit flush.

andy

03-02-2006, 01:20 AM

I'll get some exact measurements in the next few days. I'm going to be racing in the US Touring Car race at Laguna Seca (A1GP Support Race - woo hoo!) on 3/10-12, so I've got a few other details to take care of. I'll try to keep this as updated as possible, though.

The thing about the drive shaft was measured from the front mounts to the end of the driveshaft. It's not that much different, there might be enough slack to just jam it in, but I'm really going to be whomping on this thing, so I don't want it to go bad prematurely. But interesingly, even though the case is differently sized the rear diff plate does seem to be pretty close to the right place.

The width of the output shafts is interesting as well. From the pic, both diffs' output shafts are pretty flush. The interesting thing is comparing the two to my '91 318is - it has a small case diff and huge flanges sticking out several inches. e30s, I think use all the same length shafts, while e36s seem to vary. I may be cruising for Z3's to measure out there, but I'm heading to the junk yard tomorrow morning...

Oh, and I'll start another thread on gear ratios, there are some interesting things about that too. Yes, in general BMWs and particularly those with semi-trailing arms work great with an LSD, whether it be track or autocross, or driving on a slippy road.

L84THSKY

03-02-2006, 01:27 AM

CaliDohBoy

03-02-2006, 01:29 AM

I understand the E30 diff is not an "easy" install... but what about E36 diffs from the ti's that came with them as Cali-ti pointed out? What would the 4.44 ratio do to my automatic?

cali-ti

03-02-2006, 01:42 AM

When you say the to flanges stick out less than the e30 flanges, are you saying with both flanges in a ti diff? That is what I can't get a straight answer on. I'm only interested in knowing the flange to flange width of an e30 diff with the stock flanges and also the ti flanges.
no, the ti flanges in the e30 diff stick out less than the e30 flanges in the e30 diff as shown by dredder: http://318ti.org/forum/showthread.php?t=7865

the ti halfshafts are longer than the e30 halfshafts and the e30 diff is wider than the small case diff in the ti. as long as you have no issue with the strength of the ti flanges and halfshafts, i see no reason why it shouldn't work.

cali-ti

03-02-2006, 01:45 AM

I understand the E30 diff is not an "easy" install... but what about E36 diffs from the ti's that came with them as Cali-ti pointed out? What would the 4.44 ratio do to my automatic?
if you can find a ti or 1.8/1.9 z3 auto that had a LSD (again, this is a small case diff), it will bolt right in with no issues (and be the same 4.44 ratio as your current automatic open diff). it's going to a large case diff where you run into fitment issues (although not too big of issues).

L84THSKY

03-02-2006, 02:34 PM

I think I misspoke. What I want to compare is the width flange to flange of the
stock diff with stock flanges, to an E30 diff with ti flanges. Isn't that the only comparison that matters. I wanna know if the E30 diff with ti flanges is wider than stock setup. If it is, that could be a big problem. From what everyone says, the swap is no problem.

no, the ti flanges in the e30 diff stick out less than the e30 flanges in the e30 diff as shown by dredder: http://318ti.org/forum/showthread.php?t=7865

the ti halfshafts are longer than the e30 halfshafts and the e30 diff is wider than the small case diff in the ti. as long as you have no issue with the strength of the ti flanges and halfshafts, i see no reason why it shouldn't work.

L84THSKY

03-02-2006, 07:26 PM

Andy, do this simple measurement.

Measure the width flange to flange of each of the two diff in the picture, with the stock flanges. Then take the ti flanges out and put them in the E30 diff, and measure the width flange to flange.

The problem with everyone throwing their insight into the mix is, they are confusing the issue.

Anyone who has ever done an experiment knows, if you change two variables, you won't know which one did what. By swapping the SAME flanges in two DIFFERENT diff housings, we can do a proper measurement.

I keep hearing, the shafts are longer/shorter so that means ........
The flanges are longer/shorter, so that means ...........
The bodies of the diffs are wider/narrower, so that means........

It don't mean ****, if people keep comparing multiple issues and trying to come to a conclusion.

PLEEEEEZE, some one just compare the flange to flange width of an E30 diff with ti flanges, and a 318ti diff with ti flanges.

If I leave my shafts in, and remove the diff, the car will expect the diff I put in to have the same width to fit. So I don't car about the shafts, just the flanges and diff. The diff/flange combination I replace must have the same width as what was in there. The only way I will know is to do what I'm asking.

Thanks
Eric

http://www.318ti.org/gallery/showgallery.php?cat=600

1. The output shafts' flanges' holes are indeed further apart than the stock unit. I assume this is where swapping flanges comes in.

HigH RevZ

03-03-2006, 09:01 AM

if you can find a ti or 1.8/1.9 z3 auto that had a LSD (again, this is a small case diff), it will bolt right in with no issues (and be the same 4.44 ratio as your current automatic open diff). it's going to a large case diff where you run into fitment issues (although not too big of issues).

So I would have to find a sport Ti to get the lsd, correct.

cali-ti

03-03-2006, 03:23 PM

it was standard only on the 95 club sport, optional on other 95s and early 96s (i believe) until ASC+T became standard. after that, i don't believe it was even an option. likely the same with the 1.8/1.9 z3s.

andy

03-04-2006, 01:44 AM

I shall, I shall! :) I got busy last night, and I have to take the gf out tonight, but I've got all the parts sitting on my garage floor ready for measurement. Comparing the pics from the other thread, they do look shorter, but wasn't that a 5 series diff?

Andy, do this simple measurement.

Measure the width flange to flange of each of the two diff in the picture, with the stock flanges. Then take the ti flanges out and put them in the E30 diff, and measure the width flange to flange.

Thanks
Eric

andy

03-04-2006, 01:56 AM

Yep, it was a $550 option on my non-club sport package '95...I still have the window sticker around somewhere.

If someone wanted to make their automatic faster (or if you were a complete nut that only drove on tight roads) you could find a small case auto diff from an older 318 auto; I believe they came with a 4.88. A search on RealOEM would tell for sure.

it was standard only on the 95 club sport, optional on other 95s and early 96s (i believe) until ASC+T became standard. after that, i don't believe it was even an option. likely the same with the 1.8/1.9 z3s.

mischief

03-04-2006, 04:55 AM

all you most click on this link if u havent seen it allready will tell you all you need to know now click on the link
http://www.emotors.ca/articles/7.aspx

andy

03-05-2006, 09:38 AM

Here is a picture of the e30 diff with one ti flange and one e30 325 flange stuck in it.

http://www.318ti.org/gallery/showphoto.php?photo=1816&cat=600

Long and short of it is that they stick out nearly exactly the same distance; possibly less than a millimeter difference. Both measurements are 14.5mm, from the centerline of the diff to the edge of the flange.

I read through the link in the last post, and I think this guy's on to something here. Going to be busy this week, but I'll check in when I get the chance.

L84THSKY

03-05-2006, 05:35 PM

Andy

I think you missed the point. Your comparision doesn't help. I asked for a picture of the stock ti diff with stock flanges, compared to the E30 diff with ti flanges.
You are comparing two flanges on the same diff, that tells me nothing. Since the E30 diff is wider, I still can't draw any conclusions from your comparision.

Can you please just measure the ti diff flange to flange with stock flanges. Then remove the ti flanges and put them in the E30 diff and measure flange to flange. If you do that, there will be absolutely no confusion, missinterpretation or false conclusion drawn. That is the ONLY way to know for sure.

Here is a picture of the e30 diff with one ti flange and one e30 325 flange stuck in it.

http://www.318ti.org/gallery/showphoto.php?photo=1816&cat=600

Long and short of it is that they stick out nearly exactly the same distance; possibly less than a millimeter difference. Both measurements are 14.5mm, from the centerline of the diff to the edge of the flange.

I read through the link in the last post, and I think this guy's on to something here. Going to be busy this week, but I'll check in when I get the chance.

andy

03-06-2006, 08:11 AM

L84THSKY - I see, I thought it was obvious from the pics, but yes, there is a lot of conflicting information out there.

These measurements were from outside of the output flange to the outside of the output flange, for each diff.

318ti flanges in a 318ti diff (168): 25.5 cm
318ti flanges in an e30 325is (188) diff: 28.25 cm

The e30 diff is definitely wider (by about 2cm) and while the ti flanges do sit in nice and snugly, they don't sit in further to fully account for the difference in size of the 188 diff. Note these aren't super-exact measurements, I don't have any fancy calipers to measure these at home, just a few straight edges and a tape measure.

Interestingly, I swapped the flanges back afterwards, and the e30 flanges in the e30 diff were the same as the ti flanges in the e30 diff.

So, it's the above article talking about only swapping the inner e30 cv joints onto a ti axle? That'd theoretically leave us with an axle that's about a cm too long, right? Unless the hub has enough play to accept the extra axle when tightening the collar nut. Hmm....

L84THSKY

03-06-2006, 05:21 PM

Thanks Andy. That is exactly what I wanted to know. Now the question is, will the E30 diff work wih ti flanges, and the stock halfshafts? I've heard people say yes. I also saw the writeup on the website that Constant Yu swapped inner CV joints from an E30 halfshaft.

That is what I'm not sure about now. Do I keep ti flanges and inner CV joints, or must I swap to E30 flanges and E30 inner CV joints.

From what you said E30 diff with ti flanges is almost 3cm to wide, as opposed to swapping to E30 flanges and E30 CV joints; which is only 1 cm too wide.

The truth is, I have heard of people doing both, with no problems. That leaves me with doubt about what is true.

L84THSKY - I see, I thought it was obvious from the pics, but yes, there is a lot of conflicting information out there.

These measurements were from outside of the output flange to the outside of the output flange, for each diff.

318ti flanges in a 318ti diff (168): 25.5 cm
318ti flanges in an e30 325is (188) diff: 28.25 cm

The e30 diff is definitely wider (by about 2cm) and while the ti flanges do sit in nice and snugly, they don't sit in further to fully account for the difference in size of the 188 diff. Note these aren't super-exact measurements, I don't have any fancy calipers to measure these at home, just a few straight edges and a tape measure.

Interestingly, I swapped the flanges back afterwards, and the e30 flanges in the e30 diff were the same as the ti flanges in the e30 diff.

So, it's the above article talking about only swapping the inner e30 cv joints onto a ti axle? That'd theoretically leave us with an axle that's about a cm too long, right? Unless the hub has enough play to accept the extra axle when tightening the collar nut. Hmm....

andy

03-06-2006, 06:50 PM

The truth is, I have heard of people doing both, with no problems. That leaves me with doubt about what is true.

Well, the situation is probably what can be made to fit, vs. what is optimal given the different dimentions. If it's off enough on the axle to fit, yet might be causing undue wear on the diff, hub, or CV joints, then that's not something someone would discover until further down the road. There could be enough play in the system to handle a cm on each side, but we don't know that yet.

Also, I was thinking, since the 188 diff output flanges are placed further back than 168, then that could mean less of a straight shot, and a longer distance to cover making up for the wider diff.

andy

03-28-2006, 11:22 PM

Okay - finally got this to work.

1. Swapped the e30 inner joints into my ti axles. I could get them to fit in, however, when put the car back down on the ground, the axles did bind up and interfere with the suspension's travel.

2. Swapped the ti inner and outer cv joints onto the e30 axle. The entire setup was noticibly shorter than the ti axle setup. The outter CV joints are quite difficult to get undone, and we destroyed the inner clip ring getting them off. However, this did allow me to keep ABS (the old e30 axles did not have ABS) and come up with a setup that fit.

Here are the part numbers I used:

01 FINAL DRIVE 3,73 09/1988 33101211960 (from a '88 325)
01 OUTPUT SHAFT 33211226333 (from an '84 318i)

I may go with a 4.11 in the future, this is a race car afterall. But I think this should be a good start.

jonchino

03-30-2006, 06:34 AM

ok so is this what worked?

Ti's inner and outer cv joints on the E30s axle.?

plus the Ti's flanges on the E30 Dif..?

and you got the ABS to work..?

thanks
Chino

andy

04-07-2006, 09:15 PM

It was

'87 e30 325 diff and output flanges
84 e30 318i axle (all the e30s appear to use the same axle)
e30 inner cv joint, mated to the e30 diff
ti outter cv joint, mated to the ti hub as usual

Removing the outter cv joint from the ti axle was a treeemendous pain; it doesn't have a lock washer like the other end. I realize some of the writeups seem to show the e30 axle isn't longer than the ti axle. I found the e30 axle (just by itself, no cv joints on it) to definitely be noticibly shorter.

Oh, and because I did keep the ti outer joints, abs is fine.

ok so is this what worked?

Ti's inner and outer cv joints on the E30s axle.?

plus the Ti's flanges on the E30 Dif..?

and you got the ABS to work..?

thanks
Chino