Differential swap xdrive50i to xdrive35d

[Spyro235]

Originally Posted by RL18

Is the drone bad on the highway? I know my 335d deleted gets loud at 2,300rpm. Kind of makes me nervous about deleting my x5d because I don't want no damn muffler on it. I drive nearly 30-40k a year so I'd break even in no time on this mod lol. Also curious on the results for mpg though

My X5 is ATM 3" deleted, ATM's midpipe, to oem muffler. Planning on doing an electric cutout sometime when it's warm. ATM's midpipe has a resonator that definitely helps at around 76-83ish mph.. I dont have any drone at all really, and I am pretty sensitive to sounds and stuff. I have more tire noise than engine noise with my winters on. The X5d is just built better with more of a focus on dampening NVH than the 3 series. My relatively base-ish X5 is WAY quieter than my 335i premium sport was. I thought my catless downpipe 335i had a bit of drone, and my muffler deleted drift car definitely has crazy drone.

[RL18]

Originally Posted by Spyro235

My X5 is ATM 3" deleted, ATM's midpipe, to oem muffler. Planning on doing an electric cutout sometime when it's warm. ATM's midpipe has a resonator that definitely helps at around 76-83ish mph.. I dont have any drone at all really, and I am pretty sensitive to sounds and stuff. I have more tire noise than engine noise with my winters on. The X5d is just built better with more of a focus on dampening NVH than the 3 series. My relatively base-ish X5 is WAY quieter than my 335i premium sport was. I thought my catless downpipe 335i had a bit of drone, and my muffler deleted drift car definitely has crazy drone.

That's good to know . I don't plan on using any muffler on my x5d but if the drone is bad I might have to.

[smass]

Originally Posted by ucsbwsr

Yes, front shaft is in place.

My new rear dif has arrived and I am gathering needed supplies. How big is the wrench used to disconnect the rear driveshaft? I think it needs to be 2" or 50mm. Any other tips before I jump in?

Thanks

[ucsbwsr]

Originally Posted by smass

My new rear dif has arrived and I am gathering needed supplies. How big is the wrench used to disconnect the rear driveshaft? I think it needs to be 2" or 50mm. Any other tips before I jump in?

Thanks

Correct, 50mm. My tip would be look up the procedure on NewTIS.info and thoroughly read through the process BEFORE starting the project. It's pretty straight forward and it's all outlined on that site.

[smass]

Originally Posted by ucsbwsr

Correct, 50mm. My tip would be look up the procedure on NewTIS.info and thoroughly read through the process BEFORE starting the project. It's pretty straight forward and it's all outlined on that site.

Thanks for the reply. I have read the newTIS multiple times now and I think I have a plan.

[Recon3D]

Originally Posted by ucsbwsr

Yes, front shaft is in place.

Does this mean the front differential doesn't have to be swapped? I like the AWD functionality but I'm still not sure if I have to swap the front differential as well if I decide to go with the 50i rear diff. I'm getting horrid MPG (21 mpg avg) in my 35d and I think this would be a beneficial mod for me as I drive around 20k miles a year.

Besides the rear diff (# 33107590914), what else would be needed for this swap?

[ucsbwsr]

Originally Posted by Recon3D

Does this mean the front differential doesn't have to be swapped? I like the AWD functionality but I'm still not sure if I have to swap the front differential as well if I decide to go with the 50i rear diff. I'm getting horrid MPG (21 mpg avg) in my 35d and I think this would be a beneficial mod for me as I drive around 20k miles a year.

Besides the rear diff (# 33107590914), what else would be needed for this swap?

If you don't swap the front diff and you swap the rear you CAN'T USE AWD with mis-matched diff ratios, you will have serious TC and DSC issues. I recommend swapping both diffs.

3.15 should help your MPG but if you are getting that low of MPG while doing moderate highway mileage and not driving aggressively then you might have some other issues to explore like carbon build up, clogged DPF, bad thermostat, etc.

Look up the technical documentation on swapping the diffs, that should answer all your questions about the process and required parts. Personally I would recommend adding fresh diff fluid but probably best to do that once the new diff is in and after it's been used so the used fluid will be mixed up and hopefully get all the old gunk out when drained.

Evan

[Recon3D]

Originally Posted by ucsbwsr

If you don't swap the front diff and you swap the rear you CAN'T USE AWD with mis-matched diff ratios, you will have serious TC and DSC issues. I recommend swapping both diffs.

3.15 should help your MPG but if you are getting that low of MPG while doing moderate highway mileage and not driving aggressively then you might have some other issues to explore like carbon build up, clogged DPF, bad thermostat, etc.

Look up the technical documentation on swapping the diffs, that should answer all your questions about the process and required parts. Personally I would recommend adding fresh diff fluid but probably best to do that once the new diff is in and after it's been used so the used fluid will be mixed up and hopefully get all the old gunk out when drained.

Evan

Thanks for getting back to me, are both the differentials coming out of the 50i? I'm just not exactly sure what else might be needed besides the diffs to fit them to the 35d. I'll try looking up to see if I can find anymore info on this.

My mpg issue is kind of weird, I recently replaced the thermostat as that failed open, however, it didn't do a whole lot to my mpg. The thermostat now works properly and gets up to temp. I'm not sure if it's a clogged DPF, I've been monitoring my DPF with bimmer-tool and it appears that there's not that much ash/soot. I also checked my manifold for CBU, while there was a little cbu, it's nothing crazy. and I'm starting to think it might be related to my heavy 20" Style 168 wheel setup.

Regardless of the MPG, I usually cruise around 75mph on my freeway commutes and the RPMs get pretty high so that's also a reason I want to go forward with the diff swap

[smass]

I have a 5.0 rear diff that I can sell. I changed my mind on the project when I moved from flat FL to hilly AZ.

You will need a front diff from either a LCI 35i or 50i. It is the same. And a front driveshaft if you have the old style one. My 2009 has the old style.