Its been a while since I've had a chance to work on the BMW, but there've been a few teething issues with the car, so its time to dig back in. First up is refurbishing the rear differential, as the MkIII Supra LSD we installed wasn't doing much of the "L" part anymore. I got stuck on some ice out at BWDS last winter and it was pretty apparent that the rear diff wasn't coupling both rear wheels together. I also noticed at a rally-x event this summer that the car really felt like it was chugging in the loose stuff, and you could feel the car surge a bit as the tires would find traction.
Here's a shot of the diff bolted up in the car:
Yanked out of the car with the rear cover removed - these things smell terrible and the fact that it was a $40 diff from the local pick'n'pull with unknown mileage didn't help!
One of the "nice" features of the OEM supra diff is that they weren't shimmed very tightly from the factory. This cuts down on diff chatter in parking lots and when making tight turns and more importanlty it also means that the diff plates weren't really subject to all that much wear. Here's half of them after getting a good de-greasing:
This is where the magic happens. The OEM diff used a spring in the middle. The kit I purchased gets rid of that and uses a spacer and two belleville washers which act sort of like very stiff springs. According to the guys who sell the kit, breakaway torque increases up to 250 lbs, so this thing should be pretty solidly locked now.
Another shot of the diff gooing back together. You do need a backlash gauge to make sure the tolerances are all in line, but we found the instructions with the kit were right on with what shims to use:
One final shot before the rear case was re-installed:
It'll be a couple weeks before we get to test the diff out, but should 250 lbs breakaway prove to be more than we want for a rally application, they also have a milder kit that'll bring the breakaway torque to 100 lbs, which is still better than the factory setup. The good news is that with replacement diffs being so cheap and available in both 3.9 and 4.3, if I don't love it, I can always build another one and save this one for drifting.
Thanks for reading!
Dave
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Got to finally get the car out and race. Here's a short video of our near disaster:
Beautiful catch. It looks like you would have been tumbling for a while. Any damage?
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Beautiful catch. It looks like you would have been tumbling for a while. Any damage?
When I tried to kick the bumper back into position, the weld on the frame rail that holds the bumper beam tore and there's a little chipped paint on the bumper. Mudflap has a partial tear too. I haven't had a chance to put the car up on a lift yet to see if there's anything under that got tweaked, but I'm hoping I got lucky.
Dave
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Great vid, amazing driving... So glad to see the project really come to fruition... Thanks for sharing!
__________________ James 95 active w/leather interior and sport interior conversion, Vaders, full M-Tech exterior conversion. Now m50 swapped* Eibach sway bars, D2 Coilovers, Depo's w/AE's, blacked-out sides and grills, LeatherZ console and door armrests, 1 series starter button mod, and custom finished Style 5's <--- in this color! Named "Roddy": *M50 6 cyl. swap with fan delete, S50 cams and chip, AFE stage 2 intake, M3 clutch and 11.5 lb Fidanza flywheel, 3.15LSD, battery relocated to rear and complete custom exhaust. Sweet! 97 318ti sport, Alaska Blue, Contours, coilovers, Dove Vaders and custom black/grey interior named "Max" 95 318ti Active in Cosmos, S50 swap in progress... named "Pit" SUPPORT 318ti.org! CLICK THE LINK ABOVE! Hosting a forum like this is not free. 318ti.org is one of the best BMW forums on the web because it is member supported, not vendor supported. The cost to become a Supporter is a nominal $10.00... A YEAR! DO IT! NOW!
As for the motor mounts, that's a pretty simple job. I'd either go with OEM M3 mounts or try to find a bolt-through design. The aluminum motor mount arms are a crappy idea IMO. BMW should've used steel. When I bought my wrecked M3, one of the arms was snapped as well as the transmission crossmember. The opposite rubber motor mount was sheared in half also, so the engine was literally resting on the steering rack.
BMW designed it this way, so the engine can break free of the car on impact. it is less likely to come through the bulkhead and crush you. more likely to go off down the road.
Just read this thing in its entirety, What a build! I'm doing something similar with a M52 2.8 here in the U.K with my 316i compact for stage rallying and single events mainly on gravel. turreting the rear arches, fitting ford escort group 4 bilstein shocks and e30 touring springs, rather than coilovers. and fabricating my own coilovers on the front using standard 328i legs, escort weld on spring tubes and escort bilstein damper inserts. works out a lot cheaper as its hard to find gravel spec suspension for these cars over here. good luck with all the rallying. best sport in the world :-) T
My home computer is fubar'd so a buddy of mine edited up some video of our race a couple weekends ago. Not my finest driving as I realized Saturday afternoon that my brakes were no longer capable of locking up the tires, so dialed it back a bit on braking zones for Sunday's runs. Still managed to stay out in front of the other 2wd rally guys by ~6 seconds.
On the brakes - turned out that the front master cylinder was starting to leak past the seals and onto the floor and my 'firm pedal' was actually the pedal bottoming out on the mount. Got a new master installed and bled last night so I've got no excuses this weekend. Hoping for a little moisture on the road so its not super dusty. Current 2wd record is held by a Neon SRT set a few years ago.
Dave
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Need to thank my wife (and navvie) Allison for knocking out the post event recap. The formatting isn't carrying over to the forum post terribly well, so if you'd like to see the prettied up version, please feel free to check it out on our website: http://racekern.com/temple-canyon-2013/
We got some good seat time in with the Colorado Hillclimb Association at Pueblo Motorsports Park a few weeks ago, but this weekend was the first real hillclimb of the season. Temple Canyon, located just outside of Canon City, is a fun and challenging all dirt road. Since we’ve taken a number of years to get the BMW ready for dirt racing, we missed out on this race it was great to be back!
The BMW hanging out in the natural habitat of Canon City
Practice went pretty well as we got to know the road again. There were a few cautions for mud pits since we’ve been getting some rain. Those dried out quickly, but sadly that meant so did the tacky road surface as well. The last run of practice day got cancelled because of more rain and hail. Oh well, means beers and hanging out a little earlier plus, our time from our last run had qualified us 1st in Rally 2WD.
A little taste of the twisty & narrow road
Upon arriving for Race Day the next morning, folks started noticing they had been tagged with Caswell stickers. Not sure who the culprit is, but no Bill sightings at the race. After noticing ours on the trunk, I was just going to pull it off, but Dave and I made some “enhancements” to the sticker instead.
We put on some fresh tires on (for those of you that know Dave well … aren’t you proud of him?!) and were ready for Run 1. It was already hot and dry. First run went very well – surprisingly. We felt like we got a few corners better than practice, but a few others not as well. We expected a similar if not worse time from qualifying. Instead we went from a 3:42 to a 3:35. That was enough to break the standing 2WD drive record for Temple Canyon. That’s 2 for 2 on breaking records this season!
The Race Day timing board
We had been hearing some pretty awful clanging sounds throughout practice. Our exhaust had some issues at Pueblo and we had taken it off. Hangars were reinforced before Temple Canyon and we chalked up the noises to ‘self clearancing’ due to the slightly less hangar sag. It started to sound really bad after our first Race Day run though and Dave got the car up on jack stands to have a look. Turns out our Supra differential was starting to crack its custom mounts! No bueno. Everything was still intact, meaning it was repairable with reinforcement. We didn’t take the risk of a second run given we felt lucky to have noticed it when it was in a relatively easy fixable state. If we took another run and it busted through, like it wanted to, the repair would become much nastier and more expensive. Furthermore, if it did bust mid run, that sort of loss of control of the car could result in a season-ending type crash. Temple Canyon is unforgiving, and there are only so many piles of kittens (picture at the end if you don’t know what I’m talking about). Feeling good about the first run, we saved our car and hoped we could hang on to first place. After our class took their second run without us, we were pleased to see that 3:35 hang on to win the race.
Devon (AfroThunder) Dobson captures a nice action shot!
Overall it was another great weekend racing, thanks for reading!
Dave
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That's freakin' awesome! Any plans to put on that Harry Hockly kit?
Thanks! Yes, I'm still planning on installing the kit, just wanted to wait till I've got some miles under my belt before putting the spendy bits on the car.
Dave
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*M50 6 cyl. swap with fan delete, S50 cams and chip, AFE stage 2 intake, M3 clutch and 11.5 lb Fidanza flywheel, 3.15LSD, battery relocated to rear and complete custom exhaust. Sweet! 
97 318ti sport, Alaska Blue, Contours, coilovers, Dove Vaders and custom black/grey interior named "Max" 95 318ti Active in Cosmos, S50 swap in progress... named "Pit" SUPPORT 318ti.org! CLICK THE LINK ABOVE! Hosting a forum like this is not free. 318ti.org is one of the best BMW forums on the web because it is member supported, not vendor supported. The cost to become a Supporter is a nominal $10.00... A YEAR! DO IT! NOW! 
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