I swear that they aim for me!! [emoji1787][emoji1787][emoji1787]

I was actually pissed more about the cost as it is normally about 50 USD but needs must when the devil drives (and you're in a hurry)

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What have I done to my X5? Nothing for a very long time.

It will be 3 years this Feb. that I parked my X5 to do some mods. It has been on my to do list all that time. To do list is always pretty long so I always have an excuse not to do the work. I see the parts every time I am in the garage. it's raining, maybe today is the day, maybe not.

Does anyone know if 4.10 differentials from a 01 3.0 are a direct fit in an 02 4.6?

I am 90% positive that they are, with the only difference being the ring and pinion.

Only problems may be case spacing bump on the rear (doubtful but possible) and how will the transfer case gearing react to different gear sets (settings/gears need changed?)

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I would think that the different ring gears will fit in the generic e53 diff carrier, but you’ll need to change the pinion too I think. The pinion tooth count and spacing must match the ring gear tooth count and spacing. Changing the pinion bumps a diff rebuild up by an order of magnitude, in my opinion. New bearings, seals, crush sleeve, etc, etc. and don’t forget the special bearing puller to get your old bearings off.

On the other hand, I decided to leave the pinion in my eBay diff that I used and now have a faint whine at 30 to 35 mph. Good chance it’s the pinion…that I should have rebuilt. We’ll see how the oil looks when I get the x home. If it’s mud and chunk free after a 2000 mile drive, I’ll likely live with the whine for a while.

The front and rear final drive ratios must match obviously, so you’ll need to change them both. Unfortunately the front diff carrier and ring gear are different than the rear. Standard BMW harassment package. The front ring gear has fewer bolts and a smaller diameter from what I can tell.

since it was parked close to my garage and I was rebuilding some forks that needed ATF, I decided to flush the power steering. The stuff that came out was still reddish, but a whole lot thicker than what I put back in.

So far drained and filled the reservoir twice, I guess I'll do another flush in a few days to see what the fluid looks like.

The new suspension was clunking a bit and I still had a wobble, so took it back to the mechanic and he re-tightened everything and balanced the front wheels. Much better now!

I have the differential cases with the gear sets in place so I can switch out, swap, the two 3.91 cases for front and back 4.10 cases without having to do any mods. The question is if anyone knows if they are interchangeable.

So you have two complete diffs, both front and back, in the ratio you want? I thought you wanted to swap ring gears and pinions, sorry.

I think it should work just fine other than your speedometer being off. Lots and lots of final drive swap threads over on bimmerforums.com. I bet you could find the details there. I’d love to know definitively too.

There are at least a few threads where the 4.1 <> 3.91 swap has been done. I thought I recalled one minor issue where the drive shaft connects to the differential but search for a thread covering the topic.


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I dug out my car from the snow - nothing else to do today besides post on forums. It's one degree outside (count em, one!) and way too cold to do anything outside other than shovel.

Alright the X did fantastic in the snow as always - or at least as it always has since I put snow tires on it. Got to teach my 2nd grader what "getting sideways" means. Have about 14-18 inches of pure powder and temps hovering around 0 F here today.