Swap diff gearing for lower ratio & convert to rwd?
 

After an 800+mile road trip last weekend in my new-to-me E53 M54 manual I realized this thing is NOT geared for highway driving. 5th is 1-1, not overdrive, so at 80mph I'm turning almost 4,000rpm with that 4.10 final drive.

Is a diff gear swap possible, and would it be possible to disconnect the front diff and driveshaft? I don't need AWD here and have no plans to off-road this beast other than basic dirt/gravel roads.

I suppose another option would be a gearbox swap from a post-LCI E53 6-speed, but unless there's another box that will fit there's probably fewer of those left than pre-LCI 5-speeds, if that box is specific to the E53 in general. I have no idea.

You can just get differentials from the V8, which had lower final drives, if you really want to. But are you worried about fuel economy in your E53? You know, we kick you right off this board if you talk about fuel economy. Right off. We get kickbacks from the Saudi Royal Family for how much revenue we generate.

Other than the $100 first fill-up surprise as I'd run it nearly empty, no, fuel economy isn't the issue here. It's the engine noise; running at 3500/4000rpm for hours is tiring for it and me. The gearing in this thing is agricultural.

The t-case won’t let you just disconnect the front drive shaft. Best bet is to look for some V8 diffs like bdc said.

Here is one thread on the topic...A move from 4.10 to 3.64 sounds like the ticket...
https://xoutpost.com/bmw-sav-forums/...i-3-0-5mt.html

And another one:
https://xoutpost.com/bmw-sav-forums/...omponents.html

As recommended, used 4.4 diffs are your best bet I think. You may be able to find gearing for the rear to swap in, but I don’t think anything other than custom will work on the front.

First time I've heard of 3.64.

My 3.0 was about 2600@75. I didn't realize the MT had such a high gear ratio for top gear.

3.64/4.1=0.888
3.91/4.1=0.954

11% vs. 5% drop in rpm but also launch performance.

The pre x - drive not simple to convert to rwd butt people do it.

3500*.88=3080
3500*.95=3325

Food for thought

Yes, 5 speed does not have overdrive. They fixed that in 2004-2006, which has a 6 speed manual. You could find one of those.


From what I remember, each engine offered for e53 has a different ratio in the differentials, which means 4.4 and the 4.6 have different final drive. Also, E53 transfer case does not care for missing inputs/outputs. If it's the tcase with no actuation motor (the early one), you will get no forward power at all if even one axle shaft comes out of a diff, much less a missing driveshaft. It's not a 70's dodge.



I once looked to see if e46 awd (330ix) ratios were any good, and if their diffs would swap, since they share the m54. you could look into that. They would have to be geared numerically lower than 4.10.


I don't think my e53 did 4k rpms at 75 on the highway, but its been so long since it went that speed, I couldn't say.

If you truly want to ditch the awd then why not look for a manual box out of an e46 or e60. The 535d manual boxes are super stout. Just keep the front diff unless you’re in for the challenge to delete that as well.

All the best! Just don’t overthink it and do it����

trying to match engines/gearing/mileage to whatever I needed
 

I drove 7 other vehicles on a regular basis, before I got the X5, over the last 25 years, that make me appreciate the overdrive ratio of my X5's auto transmission, especially since the final drive is 4.10!

Here's the lineup of my vehicles, past & present, of which the X5 has neither the best nor the worst rpms at 75 mph (listed from most rpms to the least):

• 1) 1966 Chevy Chevelle Malibu, 441 c.i. (7.2L), 2WD, TCI Powerglide/Transbrake,
  4.88 final drive (full-spool diff), with MT 28/10.5-15 tires (28") drag, 275/60r15 tires (28") street
  First: 1.76 (8.59), Second: 1.00 (4.88)
  4392 rpm @ 75 mph
  
  
• 2) 1986 Chevy S-10 Tahoe Ext.Cab, 173 c.i. (2.8L), 2WD, TH700r-4, 3.42 final drive,
  with 255/60-15 tires (27") rear...215/65r15 (26") front
  First: 2.74 (9.37), Second: 1.57 (5.37), Third: 1.00 (3.42), Fourth: 0.667 (2.28)
  3192 rpm @ 75 mph
  
  
• 3) 1969 Chevy C-10, 355 c.i. (5.8L), 2WD, Turbo-Hydramatic 350, 3.73 final drive,
  with 30/9.5r15 tires (30")
  First: 2.52 (9.40), Second: 1.52 (5.67), Third: 1.00 (3.73)
  3133 rpm @ 75 mph
  
  
• 4) 1975 Chevy C-10, 358 c.i. (5.9L), 2WD, Turbo-Hydramatic 350, 3.42 final drive,
  with 275/60r15 tires (28")
  First: 2.52 (8.62), Second: 1.52 (5.20), Third: 1.00 (3.42)
  3078 rpm @ 75 mph
  
  
• 5) 2001 BMW X5 E53 3.0i, 182 c.i. (3.0L), AWD, 5L40-E, 4.10 final drive,
  with 235/65r17 tires (29")
  First: 3.42 (14.02), Second: 2.22 (9.10), Third: 1.60 (6.56), Fourth: 1.00 (4.10), Fifth 0.75 (3.07)
  2672 rpm @ 75 mph
  
  
• 6) 2009 Chevy HHR Panel LS, 134 c.i. (2.2L), FWD, 4T45-E, 3.91 final drive,
  with 215/55r16 tires (25.3")
  First: 2.96 (11.57), Second: 1.626 (6.36), Third: 1.00 (3.91), Fourth: 0.681 (2.66)
  2652 rpm @ 75 mph
  
  
• 7) 2004 Chevy Silverado 2500HD WT (reg.cab), 364 c.i. (6.0L), 2WD, 4L80-E, 4.10 final drive,
  with LT245/75r16 tires (30.5")
  First: 2.48 (10.17), Second: 1.48 (6.07), Third: 1.00 (4.10), Fourth: 0.75 (3.08)
  2451 rpm @ 75 mph
  
  
• 8) 1998 GMC Sierra Ext.Cab, 350 c.i. (5.7L), 2WD, 4L60-E, 3.73 final drive,
  with 275/60r15 tires (28")
  First: 3.059 (11.41), Second: 1.625 (6.06), Third: 1.00 (3.73), Fourth: 0.696 (2.60)
  2336 rpm @ 75 mph

I had a long commute to work (120+miles, round-trip), for 14.5 of those years, and another 3 years (70+ miles, round trip), before retirement 7.5 years ago. And I towed my race car many miles for 11.5 of those years, too. I used a lot of gasoline.

The best commuter car was my '09 HHR panel, which I used as daily driver from '09-'16, when I replaced my '04 2500HD as a daily, bought due to $4 gas prices in late '08. The worst was my '66 Chevelle, which I had to drive a few times to work, when other choices were few (OK when it had a 327 c.i. engine and 3.38 final drive, became expensive to drive when it got the first 427 c.i. engine and 3.73 gears, and impossible when it got the bigger 441 c.i. engine + 4.56, and later 4.88 gears ...with a locked differential, and 5 gallon fuel cell/118 octane fuel.

The '86 S-10 was strictly a commuter too, with a wimpy tow rating, so I bought my first C-10 to do double-duty, commuting and/or towing, back in 1997. I restored/modded the '69, but found that the hi-po 355 engine used a lot of gas, and I got the '75 C-10 with lower compression engine, and lower gearing to use mostly for long-range towing. Never finished restoring it (despite the new engine and running gear), so it was my back-up commuter (topper on the back made it alright for overnight stays at work during ice storms...the HHR was much better, though).

Since retirement from racing in '08, and from work in Jan.'16, the '04 2500HD has been relegated to towing trailers (we've got a '98 GMC as back-up), the '09 HHR has been the grocery-getter and wife's eveyday vehicle, and the recent (2 years ago) acquisition of the X5 made it my seldom-used project/daily?? driver vehicle.

Why do I feel that the X5 gearing is fine as it is? As few miles as I drive it around town, it doesn't matter much if the HHR (or GMC) get better mileage, and the 2500HD with the 6.0L engine and same final gear gets much worse mileage about town and even worse than the X5 on the few highway trips it's gone on.

The X5 was going to replace the HHR (daily driver & go-getter), 2500 HD (2250 lb. camper towing), and GMC (people hauling, as it was the only 4-passenger vehicle, previously) functions, as I envisioned it 3.5 years before getting it. Meanwhile, my health limited my camping, personnel changes in the family negated the need for 4+ seats, and neither my wife nor I travel even a fraction as many miles as in the past years. So, I have vehicles aplenty for uses I no longer need them for. But, the X5 is here to stay, regardless of rpms or gas mileage.