They probably could, but I'd guess that would involve ordering different parts so could increase the costs.
I'm currently running a diff from a Mk III Toyota Supra because I wanted to gear the car for a 120mph top speed. All the ring & pinion sets over a 4.27 are "motor$ports" parts, so I was looking at over $1000 for just the gears. I had some custom bits made (mounts & driveshaft) and even had a diff built for that same amount of money. If I had it to do over again though, I'd stick with the BMW medium case diff and go with a ratio in the 4.0 range because of the torque curve of these motors.
Dave
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Factory diffs are set for 25% lockup. I've seen aftermarket diffs setup with 40%. slow_ti added one or two clutch discs to his diff which supposably gave him a higher locking percentage. I'm not too sure about this method as I don't know if it will put too much load on the bearings and such. There are companies that sell replacement discs, but shimming, preloading and setting backlash on diffs is not my area of specialty. Of course you could always weld the diff and get 100% lockup, but that will compromise handling.
Factory diffs are set for 25% lockup. I've seen aftermarket diffs setup with 40%. slow_ti added one or two clutch discs to his diff which supposably gave him a higher locking percentage. I'm not too sure about this method as I don't know if it will put too much load on the bearings and such. There are companies that sell replacement discs, but shimming, preloading and setting backlash on diffs is not my area of specialty. Of course you could always weld the diff and get 100% lockup, but that will compromise handling.
The welded diff would actually be ok for sideways driving...but from my friends that have tried it, life is tough on the axles and they fail much more often. I found this today when searching for replacement diff guts:
BMW is done playing on the ice for the year. Loaded it up last night and towed it back to Denver. I'm a little bit sad, but looking forward to getting it back on some grippy stuff. Here was a video my buddy put together from the play day last weekend:
Found out I've got some more work ahead of me. The LSD I got from the junkyard doesn't limit anything. I need to tear into it to see what's going on, but 1wd on the ice is s l o w coming out of the corners. Sorta kicking around the idea of finding a 3.9 diff instead of the 4.3. With the torques of the inline 6, I don't think I'll hamper the performance much by gearing it back down...and it should help with the massive amounts of shifting I've been doing. Most of the time on the ice, I just put the car in 3rd and left it there. Torque is fun!
In addition, the throw out bearing is making all sorts of terrible noises, so I'll need to tear the transmission off the car shortly and figure I'll drop a new clutch disk in there, as the one in there currently was a used unit. Good enough for goofing around, but not something I'd trust to an $800 entry fee, 4 days off work, and 1500 miles of towing.
Dave
Contact Brett at Koala as he does wonders with diffs and has plates and clutches made to his spec and just swapping them in gives you about 40% with no worries and they are much tougher than stock.
I'm no longer using a BMW diff. A big part of the reason behind that move was the outrageous costs of getting BMW parts serviced. I had a Toyota diff bought, rebuilt, and a new ring and pinion put in for $450 shipped. Unfortunately my diff mounts weren't quite right and i killed the unit as a result. I've been using a $20 one from the junkyard for the last 10 months.
Dave
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The car is awesome to ride in and drive! I love it! Will be great on rally stages where you'll spend most of the time popping between 3rd and 4th gear. A 3.90 diff might be good for really fast events though. Trying to go check out the white ti on here and CL over near city park, but no response back from the guy yet. Might be fun to eventually have two similar rally cars...
Last edited by granthughes; 03-02-2012 at 03:54 PM.
Had a chance to get the BMW out for the season opener for the local rally-x group. I drove the Evo but let my buddies (Grant and Josh) wheel the BMW around the course. Was a good day and we drove the cars back onto the trailers at the end of the day.
More of a writeup here, along with pics and links to videos:
Next up is actually getting around to ordering up the diff parts. Currently working on a replacement daily driver so I can park the truck most of the summer. Saw diesel priced at $3.99 when out driving last night.
Dave
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Long time no update guys - been busy on the other car, but with Pikes Peak now in the books for 2012, I'm about to get back after this BMW. Here's what I was busy with all spring and summer. The BMW content is that it just might translate into some Compact parts over the winter.
Purchased some cheapie wiedbody panels for the mitsu:
Blended them in with bondo:
Made molds of the entire rear half of the car:
Add a little carbon fiber:
And out pops this weighing ~7lbs:
Then cut out sheet metal and removed the rear doors (100 lbs removed):
Add a little vinyl and time to go race:
For those interested in such things, we ended up taking 2nd place in Time Attack (behind only Rhys Millen) with a time of 10:20.
Thanks for reading!
Dave
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^^Lola^^ Pioneer radio/ Pioneer 6-Disk CD Changer/ JBL 601.1 Grand Touring Amplifier/ Bilstein Sport shocks/ Bilstein e36sedan springs/ Green LED Courtesy Lights
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