11-28-2018, 07:52 AM | #1 |
Private
19
Rep 85
Posts |
Differential swap xdrive50i to xdrive35d
On a whim I looked into other differentials for the e70 family. It appears the xdrive50i has 3.15 ratios as opposed to the xdrive35d 3.64 ratio. Anyone speculate as to whether these would bolt up onto the diesel? Would probably drop about 325 rpm on the diesel at cruising speed. Would put 70 mph at 1730 rpm, 80mph at 2030 rpm, which I think would make a nice difference, As I firmly believe the x35d is geared a bit too low, would probably make a significant difference in highway MPG.
Garnered from other posters: "The 35i also got 3.15 w/ the 8 speed but the axle shafts are smaller so the dif is different. 50i and 35d use the same bigger axle shafts. F15 diesels w/ 8 speeds also use the 50i diff" "I spent some time researching this to find the info above on the axle shafts. Here is some other info on the driveshaft part numbers. 35d, 50i, 50d, and 35i all have different rear drive shaft lengths. (1410mm, 1427, 1430 and 1445). However the front driveshafts are all the same length at 709 mm. I am unsure if the rear length difference is related to different transfer cases (ATC700 w/ 6 speed vs 45L). All rear dif after 6/11 appear to use the same locking number between the driveshaft and rear diff." Last edited by theeld; 11-28-2018 at 03:03 PM.. |
11-28-2018, 09:51 AM | #2 |
Lieutenant Colonel
1641
Rep 1,727
Posts |
Diesel = low end torque. That's why. not sure it would be efficient to do that on the 50i
__________________
2017 C63 2012 X5M SOLD: 2015 M3; 2007 X3 M Sport; 2014 X3 M Sport 35i; 2004 X5 4.4i; 1994 325i |
Appreciate
0
|
11-28-2018, 01:55 PM | #3 |
Captain
108
Rep 994
Posts |
On other cars with AWD, that folks swap gearing, often the front rear ratios must match, other wise, you need to change the transfer ratio in the center gearbox. Not to mention, if there is any computer trickery that must be done... This can't be an easy swap on a car that relies to heavily on the ECU.
|
Appreciate
0
|
11-28-2018, 06:15 PM | #5 |
Enlisted Member
25
Rep 33
Posts |
I would assume you should be fine if you swapped both the front and rear differential. If those ratios are the same the rest shouldn't matter. This is fairly interesting to me as well since I do a lot of freeway driving and it looks like used diffs are fairly cheap.
|
Appreciate
0
|
03-26-2019, 03:35 PM | #6 |
Enlisted Member
0
Rep 41
Posts |
Has anyone decided to do this yet? I do a fair amount of interstate travel as well and I think the 3.15 would definitely improve fuel economy at 70+mph.
Performance around town worries me. It seems like the transmission doesn't kickdown as quick as I would like so even now and the car feels like a dog sometimes. It would be a lot of work to do the swap and have to revert back. Last edited by Juno01; 03-26-2019 at 03:41 PM.. |
Appreciate
0
|
03-27-2019, 07:17 AM | #7 | |
Lieutenant Colonel
409
Rep 1,588
Posts |
Quote:
|
|
Appreciate
0
|
03-27-2019, 12:27 PM | #8 | |
Enlisted Member
0
Rep 41
Posts |
Quote:
While swapping to a 8hp does sound like the perfect solution I think it could be very difficult to code it to the CAS and DDE. I know some folks that do this type of coding and they are very talented so I could wrong. I'm going to continue to look into the diff swap, $500 or less for both front and rear isn't much of an investment imo. |
|
Appreciate
0
|
03-28-2019, 12:00 PM | #9 | |
Captain
304
Rep 760
Posts |
Quote:
This sounds like a WONDERFUL mod, and honestly, if someone reported that they did it and it worked, I'd start looking for the parts to do it myself immediately. I can't be the experiment on this one, as I sold my second car to daily/ tow with the D. I run mostly highway mileage, and the only con I can see to this is increased stress while towing, but with such an abundance of torque, I don't think it'd be an issue anyway. |
|
Appreciate
0
|
04-01-2019, 04:29 PM | #11 |
Enlisted Member
0
Rep 41
Posts |
Are you referring to the front diff? According to the OP the 50i and X35d have thicker axle shafts, presumably for the rear. From my research i believe the diesel and v8 have identical rear diff housings.
Last edited by Juno01; 04-01-2019 at 05:05 PM.. |
Appreciate
0
|
04-01-2019, 05:24 PM | #12 |
Private
22
Rep 57
Posts |
I've swapped both diffs front & rear.
I've got super short 4,44 gears now on my 400bhp Diesel. Rear diffs are actually all the same, small 185mm model. Even though the shafts differ, but the diffs are same. 3.0i fits to 3.0d / 3.0d fits to 35d etc Front diffs... I did my google image & ETK research and was pretty sure the 3.0i Diff will fit. And yes, it did! If the V8 housing won't fit the Diesel oil pan... You can still swap the shaft & pinion into the old housing. Last edited by rodnex; 04-01-2019 at 05:29 PM.. |
Appreciate
0
|
04-01-2019, 09:31 PM | #13 | |
Lieutenant Colonel
409
Rep 1,588
Posts |
Quote:
Thanks Last edited by smass; 04-01-2019 at 09:37 PM.. |
|
Appreciate
0
|
04-02-2019, 12:26 PM | #14 | |||
Enlisted Member
0
Rep 41
Posts |
Quote:
Quote:
When I look at images of the the v8 and the x35d diffs on ebay i'm not seeing any difference in size or shape. Images of the 3.0i definitely don't look like the v8 or x35d. Not saying you're wrong just something is not adding up here. Don't want to make a purchase and have it be the one that doesn't work. Quote:
But then there's preload, crush washers, etc. Probably pretty straight forward just not something I care to take on at this time. Last edited by Juno01; 04-02-2019 at 02:28 PM.. |
|||
Appreciate
0
|
04-02-2019, 12:31 PM | #15 | |
Lieutenant
213
Rep 433
Posts |
Quote:
__________________
2012 X5d | Deleted & BRR Tuned | DWR TCU Tune | 10.25" Android 8.1 Screen
Build Thread https://www.xbimmers.com/forums/show....php?t=1529213 |
|
Appreciate
0
|
04-02-2019, 03:13 PM | #16 |
Enlisted Member
0
Rep 41
Posts |
I think speed is measured from the wheel sensors. So changing the diff ratio won't affect the speedometer but changing the overall tire diameter would.
You could still do coding to make your speedo accurate. Most if not all BMW speedometers are very optimistic from the factory. Both my 335d and x35d are 3-4 mph off at 70 according to gps. |
Appreciate
0
|
04-04-2019, 09:51 AM | #17 | ||
Private
22
Rep 57
Posts |
Nope. I've got the ZF6 but with the short diff ratio it works like a ZF8 with 2 last gears missing
Quote:
Quote:
But I'll tell you a few things... Single hybrid turbo, straightpiped, no MAF, no EGR, no Swirlflaps, XXL Intercooler, short diffs, Quaife LSD at the rear, X5M brakes all around, airride, etc |
||
Appreciate
1
9vapors663.50 |
04-07-2019, 01:54 PM | #19 | |
First Lieutenant
170
Rep 333
Posts |
Quote:
Please do. Would love to see the details of the build |
|
Appreciate
0
|
04-18-2019, 04:41 PM | #22 |
i'm just saying
5895
Rep 2,634
Posts |
|
Appreciate
0
|
Post Reply |
Bookmarks |
|
|