Diff/Gearbox Help!!

[LittleNicky]

Hello people.

I know nothing about gearbox or diff ratios, and am in desperate need of some advice.

I've put an M50 lump in my 318ti compact (1997) and as fun as the gears are.... it's basically crap!! I kept the stock 4 pot gearbox in, but i don't know whether its the diff or the gearbox that needs changing for it to feel like a normal 6 cylinder... kinda tops out around 130mph because 5th gear might as well be 4th :)


Any advice will be greatly appreciated. I do have the M50 gearbox (which i lazily didn't fit when doing the conversion) - but a diff swap would probably be easier for me (I've got fair hands... am I talking too much??). Anyway - help help help

:eek:


Nick

(bouncing sideways in 3rd, on some dead susupension)

[Bluebimma]

Diff is what you need. Grab an e30, z3, or an e24 differential. The best suited is the E24 3.25lsd.

[cooljess76]

Well you posted in the proper section, did you happen to read any of the threads?

Here's a little help, 5th gear is 1 to 1 on both Getrag and ZF transmissions, so swapping the tranny is usless as far as RPMs are concerned. US 318ti's with manual transmissions came with 3.45 diffs while models equipped with automatic transmissions came with 4.44 ratio diffs. You can google "BMW final drive calculator" and find out which ratio best suits your needs. Most of us with 6cyl swaps are running either 3.46 or 3.25 ratios in the rear end because it keeps the rpm's at a tollerable level at highway speeds. 318ti's came stock with small case diffs. It's recommended to replace it with a medium case diff and shorter halfshafts to handle the added torque of the 6cyl engines. Before you go out and purchase a medium case diff, it's important to know which ones are compatible with the Ti. E36 coupe and sedan diffs WILL NOT FIT on the Ti as they have different mounting points. The Ti shares a similar design as the e30 and Z3, however those diffs do not come with 3.46 or 3.25 ratios. Manual transmission e30's came with 3.73 final drives while automatics came with 4.10. Both are significantly higher than the Ti's stock ratio, which means increased rpm's. Most people want to lower the rpms or keep them near stock. E24's came with 3.46 diffs and e28's came with 3.25. The cases themselves have the same mounting points, however the rear cover will not bolt up to the Ti and the output flanges won't bolt up to e30 halfshafts. I used an e24 3.46LSD with an e30 rear cover, e30 output flanges and e30 halfshafts. It fit perfectly and the RPMs will be very close to stock. Since the medium case diff is wider than the small case diff, you'll need shorter halfshafts. E30 halfshafts are the perfect length and are slightly larger in diameter. Ti halfshafts can be forced to fit, but I strongly recommend against it because it puts excessive strain on your CV joints. Since the e30 halfshafts are larger in diameter, the ABS tone rings are also larger. This means that you will need to shim your ABS sensors so they don't contact the tone rings and become damged.

So you need to figure out which diff you want. You might as well upgrade to a limited slip diff(LSD). Medium case to handle the torque of the 6cyl. Remember that BMW 4cyl models came with small case diffs and 6 cyl models came with medium case diffs. European models came with all sorts of wacky final drive ratios, so you'll need to figure out what's available and which model cars they came on. Remember the Ti shares the same mounting points as Z3's and e30's. E24 and e28's have the same mounting points except for the rear cover and output flanges, they can be made to fit by using e30 parts. The higher the ratio, the higher the RPMs will be. 3.45=3800rpm @ 80mph, 4.10=4500rpm @ 80mph. 3.73 will be somewhere between that and 2.93 will be way less.

I feel like a broken record repeating this information, please search this section as I'm certain that any question you might have has already been answered.

[LittleNicky]

yeah you're heavy man!!

that was a plethora of information - i'm sorry for not reading the threads, i've been drinking wine and didn't want to tire myself out searching...


you lot are gods!! i'm never leaving this forum


:)

[Bluebimma]

I covered a lot of that info in the diy also, that thread is full of info

[cooljess76]

I totally understand, it's a lot to grasp all at once. It's not always as simple as reading just one thread because the information is usually spread out over several. And even then, it's easy to overlook certain things that may be critical to doing the job correctly. Bluebimma's E28 diff install DIY (http://www.318ti.org/forum/showthread.php?t=21516) thread is one of the more helpful ones as he goes through the whole installation process with plenty of pics. There's a couple other helpful threads posted by roadrash. One is a discussion thread (http://www.318ti.org/forum/showthread.php?t=28910) addressing FAQ's and the other is strictly a list of successful setups (http://www.318ti.org/forum/showthread.php?t=28958&highlight=differential) in regards to compatibility.

[LittleNicky]

5.7 litre??? that is gully, man!


Shaun Taylor Racing (Norwich, England) have just fitted a 6.2 LS3 into one... its mental what people are doing to these lil go karts!!

thanks again for the help guys - i'll have a look at those links you sent Cooljess



=]

[MacUser]

While we're on the topic ... I've read a number of threads on diff changes, but I still have a few questions ...

1. It sounds like many people put an M3 diff cover on the E30 diffs. Is this mandatory? Is it for clearance reasons?

2. I saw one thread where Xenocide said '95 owners would need to whack part of their frame to make them fit. Is there something about the '95s that is unique, or will I need to whack my '96's frame as well.

3. Cooljess, I read about making hybrid ti/E30 halfshafts that (I think) use the ti ABS sensor ring and don't require shimming. Any thoughts/problems with this route?

[cooljess76]

While we're on the topic ... I've read a number of threads on diff changes, but I still have a few questions ...

1. It sounds like many people put an M3 diff cover on the E30 diffs. Is this mandatory? Is it for clearance reasons?Sigh... This comment makes me want to kick a puppy:no: E36's have totally different mounting configurations and WILL NOT FIT THE TI:
http://i135.photobucket.com/albums/q122/cooljess76/diffs.jpg

http://i135.photobucket.com/albums/q122/cooljess76/diffs2.jpg

These threads will be very helpful:
http://www.318ti.org/forum/showthread.php?t=28910
http://www.318ti.org/forum/showthread.php?t=28958

I think you might be mistaking the Z3 Mroadster and Z3 Mcoupe diff cover with an e36 M3 cover. As stated before, the M3 cover will not fit, but the Mcoupe/Mroadster cover will fit. The reason people like to use them is because they have a big ass heat sink built onto it. However, this heat sink hangs down really low and I've yet to see one installed on a lowered car that isn't chipped or damaged. Personally I would rather change my gear oil regularly and not worry about my diff cover hitting a piece of debris and spraying gear oil on my tires causing me to spin out of control or frying the ring and pinion and locking up and/or exploding due to lack of lubrication. This thread has plenty of pics of a diff install as well as pics of the Mcoupe/Mroadster "finned" cover:
http://www.318ti.org/forum/showthread.php?t=21516

2. I saw one thread where Xenocide said '95 owners would need to whack part of their frame to make them fit. Is there something about the '95s that is unique, or will I need to whack my '96's frame as well.YOU DO NOT WANT TO WHACK YOUR FRAME or any structual part of the car for that matter! Yes, '95's have clearance issues. I haven't heard of '96's, '97's, '98's or '99's having clearance issues. You might be the first, if so it's HAMMERTIME:wink:

3. Cooljess, I read about making hybrid ti/E30 halfshafts that (I think) use the ti ABS sensor ring and don't require shimming. Any thoughts/problems with this route?
Never heard of such a thing. For starters, I don't think the ABS tone rings are removable from the halfshafts. Second, even if they did come off, the e30 halfshafts are much larger in diameter, so I don't think a Ti ABS tone ring would even fit over the e30 halfshaft. Regardless, it'll be 10 times harder to swap the tone rings than it would be to make a couple shims or just use a washer.
http://www.realoem.com/bmw/showparts.do?model=CG73&mospid=47506&btnr=33_1106&hg=33&fg=25

Hope this helped, sorry if I sounded grouchy I'm just waking up from a nap:wink:

[MacUser]

Sigh... This comment makes me want to kick a puppy:no: E36's have totally different mounting configurations and WILL NOT FIT THE TI:

Sorry! Don't kick the puppy! I misspoke ... err... mistyped! I meant to say "M-coupe", not "M3" cover, but I think you answered my question later ... save money by NOT buying a cover that's likely to get damaged and apply the savings to diff maintenance instead.


YOU DO NOT WANT TO WHACK YOUR FRAME or any structual part of the car for that matter!
YOU ARE ABSOLUTELY CORRECT! I DO NOT WANT TO WHACK MY FRAME! That's why I asked ... because whacking my frame sounds .... WHACKED!

so I don't think a Ti ABS tone ring would even fit over the e30 halfshaft. Regardless, it'll be 10 times harder to swap the tone rings than it would be to make a couple shims or just use a washer.


Here's where I read about the hybrid halfshafts ... doesn't sound too hard (that's why I'm worried!): http://318ti.org/notebook/diff_conversion/index.html


Hope this helped, sorry if I sounded grouchy I'm just waking up from a nap
Sorry I woke you, but thanks for the advice!

[cooljess76]

Here's where I read about the hybrid halfshafts ... doesn't sound too hard (that's why I'm worried!): http://318ti.org/notebook/diff_conversion/index.html
I read that article before and I'm fairly certain that guy bought the wrong halfshafts. It looks like he bought e30 4cyl halfshafts. 4cyl models came with small case diffs while 6cyl's came with medium case diffs. Medium case diffs are much wider than small case diffs, therfore the halfshafts MUST be shorter in order to fit. In that article, the person stated that the e30 halfshafts were longer than the Ti halfshafts and if you look at the pic he posted, the halfshafts appear to be the same diameter. I'll tell you from my own experience as a guy who has personally went to the junkyard and purchased/pulled several diffs(I had 5 of them sitting on my garage floor at one time) as well as removed, purchased and installed a pair of e30 325is halfshafts, the 6cyl e30 halfshafts are about an inch and a half shorter than the Ti halfshafts and are about 1/4" larger in diameter than the Ti shafts.

The fact that that guy was dumb enough to install longer halfshafts that appear to be the same diameter as the Ti halfshafts and then went through the hassle of swapping the CV joints makes absolutely no sense to me whatsoever. The reason his e30 halfshafts wouldn't bolt to his medium case diff is because they were not made for that diff, they were made for use with a small case diff. Obviously if he would have bought the halfshafts with his medium case diff, they would've bolted up no problem. He might as well have just used the stock ti halfshafts since he didn't accomplish anything.

There's been a few people on this forum that have managed to force Ti halfshafts onto medium case diffs. As I mentioned before, the medium case diff is significantly wider than the Ti's small case diff. This is really bad. You need shorter halfshafts to compesate for the added width of the medium case diff. Forcing a pair of 318ti halfshafts onto a medium case diff puts excessive stress on the CV joints and limits the range of movement that the CV joints need to pivot when the suspension extends and compresses.

I snapped this pic when I was swapping my diff. The diff on top is an e28 medium case 3.25LSD that I eventually sold to Marv17. You can note it's an e28 diff by the rear cover that needed to be swapped in order to fit the Ti. I ended up using an e24 3.46LSD. The halshafts that are attached to that diff were pulled by myself off of an '89 325is. I later rebuilt the CV joints prior to installing them onto my '97 ti. The diff and halfshafts at the bottom of the picture is the stock 318ti diff and halfshafts. Now I understand that this pic is a little misleading because the e28 medium case diff is actually further away than the 318ti diff which makes them look the same size. I assure you the e28 diff is significantly wider, the pic is just an optical illusion. However, you can clearly see that the e30 halfshafts are much shorter than the Ti halfshafts and much thicker:
http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3625.jpg

[MacUser]

Aha! Something I didn't catch earlier .... there are 4-cyl E30 halfshafts and 6-cyl E30 halfshafts. I didn't realize that! NOW things are starting to make sense!

Any idea about these? Are these 4-cyl or 6-cyl halfshafts??
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280530653226#ht_6038wt_907

[cooljess76]

Any idea about these? Are these 4-cyl or 6-cyl halfshafts??
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280530653226#ht_6038wt_907It's difficult to tell from the pics. There also appears to be a misprint/discrepancy in the listing. Apparently they don't realize that the e30 318's came with small case diffs.

Here's some pics of my halfshafts taken shortly after I rebuilt them. Note, I personally removed these from an '89 325is along with the output flanges and diff cover and installed them on my '97 ti and they fit absolutely perfectly onto my e24 3.46LSD. Also note that 6cyl e30 halfshafts have a ridge in the center of the shaft:
http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3661.jpg
http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3672.jpg

and here's how I shimmed my ABS sensors:
http://i198.photobucket.com/albums/aa282/schwarz318ti/absshim.jpg
http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3688.jpg
http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3692.jpg

[cooljess76]

http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3695.jpg
http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3702.jpg
http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3717.jpg

[LittleNicky]

that looks like too much headache...


i'll just get mine welded, unless i can find a Z3 lsd (small case) that'll swap straight in???

[cooljess76]

that looks like too much headache...


i'll just get mine welded, unless i can find a Z3 lsd (small case) that'll swap straight in???That's retarded. Unless you only plan on going in a straight line, your stock open diff will offer better handling than a welded diff.

[LittleNicky]

well i'll leave it as it is!


*yawns*

[MacUser]

http://i198.photobucket.com/albums/aa282/schwarz318ti/CIMG3672.jpg




Cooljess, I took a look at my halfshafts from ebay referenced above. They have that ridge in the middle. Does that mean they are definitely 6 cylinder halfshafts?

[cooljess76]

Cooljess, I took a look at my halfshafts from ebay referenced above. They have that ridge in the middle. Does that mean they are definitely 6 cylinder halfshafts?Honestly I don't know that the ridge is a distinguishing factor. If you'd like, I can take measurements of the diameter and length of my halfshafts tomorrow morning.

[Bluebimma]

Hey jess, make a note sweetie pie ;)

1995 - Frame has to be notched for the diff cover bolt
1996 - Frame has to be notched for the diff cover bolt
1997 - Frame does NOT need to be notched or the diff cover bolt
1998 - Frame -------- Oops, havent put it in yet. ;)

So far, ive noticed, the 96 is the only year ive had that wouldnt eat a ti cv from being lowered. The 97 ate two, others 95s have eaten them. 96, id say, is the golden year for a lot of the "good" parts of the ti. No secondary air system, OBDII, EWS2, recessed kidneys, frame setup in rear is good, there are a few other things ive noted in other threads, especially on bfc, but dont remember them off hand. 95 was an amazing year because you can swap ANY engine in there and be legal. ;)

[MacUser]

1996 - Frame has to be notched for the diff cover bolt

... recessed kidneys

Crap! Is this a very involved process? Does this significantly weaken the frame?

I thought most people liked to newer kidneys? Personally, I prefer the recessed kidneys, too. I just thought I was weird!

Cooljess, it would be great if you could get me those measurements!

[Bluebimma]

I took an sir chisel to mine and notched where the bolt needed to sit. It's and insignificant mod to structural integrity.

[FMD]

Another correction: All E30 half-shafts are identical, doesn't matter if it came from a 4-cylinder or 6-cylinder. They're both the short-length thick-diameter half-shafts that are desirable for 318ti medium case diff swaps.

In the case of the 4-cylinder E30s with small case diffs, the output flanges stick out farther by whatever the difference in width is vs. the medium case E30 diff.

[cooljess76]

http://i198.photobucket.com/albums/aa282/schwarz318ti/e30halfshaft.jpg

[wolferj-RIP]

Crap! Is this a very involved process? Does this significantly weaken the frame?

I thought most people liked to newer kidneys? Personally, I prefer the recessed kidneys, too. I just thought I was weird!

Cooljess, it would be great if you could get me those measurements!

I took an sir chisel to mine and notched where the bolt needed to sit. It's and insignificant mod to structural integrity.

my 95 needed just a little persuasion for everything to clear...

http://i287.photobucket.com/albums/ll133/wolferj/IMAG0006-1.jpg

[MacUser]

Everything with my swap went well .... with one exception. I had mine professionally installed. They fabricated the shims as above. Now, every once in awhile, when I'm coming to a stop there is a vibration in the pedal. It only seems to happen when slowly pulling into a parking spot and coming to an easy stop. I suspect this has something to do with ABS. Any ideas?

[cooljess76]

Everything with my swap went well .... with one exception. I had mine professionally installed. They fabricated the shims as above. Now, every once in awhile, when I'm coming to a stop there is a vibration in the pedal. It only seems to happen when slowly pulling into a parking spot and coming to an easy stop. I suspect this has something to do with ABS. Any ideas?check the sensors, wires and their connections.

[mr2v6.racer318ti.driver]

well i'll leave it as it is!


*yawns*

dude
rock a 245/45/17 tyre and you will be fine with the rpms

[bmorekirby]

i am so glad i just read this. thanks cool jess. i just bought a LSD off ebay which was listed as a small case 3.45 lsd out of a e36, and but has the e36 mounting points.