Upgrades: differentials and limited slips!
 

Had a '03 3.0i 5 speed manual for about a year now.

The gearing is awful from the factory!

4.10, waaay too short for comfortable highway cruising and 1st is mostly useless!

So what to do?

Time to swap in better ratios and add a limited slip!

What gearing to use? 3.64 is ideal and available from the factory in 4.4i cars! You could go to 3.46, we did this on an '01 5 speed, but it's a little too tall! You also have to custom build the differentials because there is no factory option for 3.46 X5 medium case!

Why add a limited slip? Because I avoid DSC, much better to have a seamless mechanical torque transfer when there's wheel slip, one that doesn't involve having the engine cut out involuntarily!!!

IN this case, we decided to just add a LS unit to the front differential, because, as we discovered with the '01, having front and rear lockers can cause massive understeer!


Process:

- Sourcing parts: I started working on this 10 months ago, bought a 3.64 rear and a 3.64 front from wrecked early E53 4.4i vehicles. I also bought a small case late limited slip (in this instance a 3.46 from a '93 318) for the front differential.

- I didn't do anything with the rear diff, just verified good bearings and installed new output seals, then installed it. Easy.

- Front diff I shipped to Jim Blanton. He built/machined the small LS to fit the front case!

- Got it back 4 months ago and went to install it, here's the old diff and the 3.64 LS:

http://i1264.photobucket.com/albums/...5/9d7a2255.jpg


- I've discovered that you don't have to drop the subframe to remove the front diff on a 3.0i! TIS is wrong. It can be squeezed in and out past the subframe!

- Once in, the front axles kept popping out. On the highway in the middle of the night. Very inconvenient!!

- also in this pic you can see the spacers I've added to the front drive shaft to help give it better contact with the transfer case splines. highly recommend doing this kind of upgrade on ANY E53 X5 to help preserve the transfer case!!

http://i1264.photobucket.com/albums/...5/ed0932bb.jpg

- The source of the problem was that we machined the front axles to accept circlips fitted in the differential, as is the convention for the early style LS unit. However, it does not produce enough tension to hold the axles in place!

- Long story short, had to pull the front diff 5-10 times and machine various parts to work the way it would have been done from the factory (and as was done on that first one we did), where the clip is on the axle itself!

End result:

The X5 is finally back on the road. There is a small gas mileage improvement! But the real benefits....The 3.64 gearing makes highway cruising much more pleasant! First gear is much more usable! I haven't been able to put a verdict on the LS front because it hasn't snowed yet!

All in all, worth it!


Some more pics from the job:

http://i1264.photobucket.com/albums/...5/e613aec9.jpg

http://i1264.photobucket.com/albums/...5/52d65fdb.jpg

Cool. Thanks for sharing. Wondering if you are seeing a change in MPG?

Cool project! What did you use for spacers on the front drive shaft and where did you get them?

awesome project but way too much time, money, and machining custom work to make it worthwhile for me.

I'll always love the fact that I have a manual X5 though, even if the gearing isnt perfect

Great ,
I had the idea for the driveshaft spacer a while back and intend to fit one sometime .
Any pics and specs you have would be a great help to the forum .

This job is cheap if you don't add limited slips! You can sell your old 4.10 units for basically what you paid for the 3.64s!


The front drive shaft spacers are small enough to allow the use of the factory giubo hardware, and keep the factory driveshaft locator in place.

I believe they are something like cylinder head bolt washers. I have tons of hardware from years of working on BMWs, I just went through and found something that works.

If anyone wants to try a set, I have plenty of them available for not much money, just send me a PM.

Any little bit of extra spline contact helps! Make sure to pull the front drive shaft and lube the splines up nice and good, too!


it improved slightly, 21mpg mixed driving versus, I believe, high 19s. This is a stock vehicle running regular gas.

Dude, you sir are my hero! :thumbup:

I have been looking into doing the differential swap for some time now. I have been putting it off thinking that I would have to remove the front sub-frame and support the front drive train from above. Great to know that I can squeeze the front pumpkin through!

Even cooler that you made the front diff an LSD. I'm interested to see how it performs when you push it. Do you have the sport package on your '03? My '01 5 speed had it and my current '04 6 speed does not. Night and day on handling.

As far as gear ratio's, I totally get it. The gear ratios are nearly the same on the '04-'06 6 speed with mild overdrive in 6th. Improvement? Yes defiantly. Could there be more improvement? I think so. Highway cruising is much better as well as fuel economy. 1st is still crazy, and I think it is prematurely wearing the syncros in 1st and 2nd on our cars. I don't know why BMW choose those gears. Towing capabilities? Weight to peak torque issues? Maybe they didn't want to create a large disparity in fuel economy numbers as to hurt sales of the larger heavier V8's or compete with the e53 diesels in Europe? Just throwing some ideas out there. Don't really know.

Can you still do soft 2nd starts? Anyways, awesome work! I'll let you know how mine turns out.

im impressed, and thanks for the pics, all info about these cars is greatly appreciated.

i think the super low first year is to get the bulk up and moving quickly, my upgrade 3.0d
sport is the same, it takes off well in first then falls into a huge hole changing to second
(auto) then all is good, it almost needs another gear between first and second

It does not have the sport pack, I have not particularly noticed a difference in handling between it and the sport pack X5s I've driven. Perhaps your non-sport X has a worn suspension..


I know for certain that changing the gears has lessened towing capability. I do not know by how much. But I pulled a 5-6000 # trailer for about 2k miles earlier this year and 1st with the 4.10s made it possible to start off on steep hills and rough terrain. However, the tradeoff for lower RPMs at highway speeds is worth it to me.

It's still going to be sluggish. The M54 needs another 100hp to comfortably move the truck. I'm thinking about a supercharger or turbo. S54 is also a possibility as those come down in price.

2nd gear soft starts are still possible with the 3.64s.

The cost of that would be much, much higher than selling your 6 cyl and buying a V8. And with forced induction, you'd probably lose any gas mileage advantage you had with the 6. In the used market there's very little price difference between the 6cyl and V8 cars now, especially with the early editions. I guess $4.30 premium gas has helped that. The V8 cars have very decent acceleration, tow quite well, and cruise effortlessly at highway speeds. I get 20 mpg on the highway at 80 with my V8, which is not too bad. Around town mileage sucks, but it's nice to have the power.

But great write up on the diff swaps.