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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 09-25-2013, 06:27 PM   #1
motorhead55
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Changed differential ratios today

As suggested here, I found a real nice 3.23 rear differential from a 325xi. My car being a 325i, 5 speed wagon, it came with the 3.46 ratio differential. A good friend of mine has a real nice transmission shop and he changed it out and installed a new rear differential mount (German Lemdorffer). What a nice change for my type of driving. I am mostly freeway and the 3.46 was just too low a ratio for freeway. I really don't feel I lost much in acceleration.
AGAIN, I appreciate the recommendations I have got here from the forum.

So......, What 6 speed and transmission shift linkage would I need to find that would fit into my wagon? Anyone here done the conversion? Can you get away without doing a custom driveline (cut or lengthen the drive shaft)?
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Old 09-25-2013, 08:02 PM   #2
lszlszx
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So your engine rpm must have dropped by about 200?
I'm guessing 2600rpm @ 70mph?

6 speed is the best for sure, you have both short ratio lower gears and tall sixth for relaxed highway cruising.
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Old 09-25-2013, 08:33 PM   #3
motorhead55
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Originally Posted by lszlszx View Post
So your engine rpm must have dropped by about 200?
I'm guessing 2600rpm @ 70mph?

6 speed is the best for sure, you have both short ratio lower gears and tall sixth for relaxed highway cruising.
I wish I was only now at 2600 @ 70. The 3.46 had me at 3260 @ 70. The 3.23 has me 220 rpm slower at 3040 @ 70. The issue with the five speed is that 5th gear is not an over drive. It is 1 to 1. That's why I am thinking 6 speed also down the road.

Last edited by motorhead55; 09-25-2013 at 08:34 PM.
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Old 09-25-2013, 09:06 PM   #4
lszlszx
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I can see why you did the swap, those are short ratios for 5th.

In fact, with the auto the engine spins at an identical 3270rpm in 4th @ 70mph.
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Old 09-26-2013, 02:26 AM   #5
Alex323Ci
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Originally Posted by lszlszx View Post
So your engine rpm must have dropped by about 200?
I'm guessing 2600rpm @ 70mph?

6 speed is the best for sure, you have both short ratio lower gears and tall sixth for relaxed highway cruising.
not sure if you meant this, but 6 speed manual is the same 1-5 with just an overdriven 6th gear.
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Old 09-26-2013, 03:17 AM   #6
Cavi Mike
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You should be able to sell that 3.46 rear end for more than what you paid for the 3.23. The 3.46 is more desirable from the performance aspect.
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Old 09-26-2013, 10:33 AM   #7
Sedan Hussein
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You'll be able to get rid of the 3.46 pretty quick if you price it right. I picked up a 3.38 a few weeks ago. Should be installing it within the next week, any troubles with the swap or was it fairly easy?
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Old 09-26-2013, 11:14 AM   #8
motorhead55
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Originally Posted by Cavi Mike View Post
You should be able to sell that 3.46 rear end for more than what you paid for the 3.23. The 3.46 is more desirable from the performance aspect.
The 3.46 I have only has 61,000 miles on it. I figured that the 3.46 were a dime a dozen.

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Originally Posted by Sedan Hussein View Post
You'll be able to get rid of the 3.46 pretty quick if you price it right. I picked up a 3.38 a few weeks ago. Should be installing it within the next week, any troubles with the swap or was it fairly easy?
The swap is fairly easy according to my friend that did it for me. I would have done it myself but my low back is a bit of a train wreck from 30 years working at UPS. My recommendations to you is to re-seal the one you are installing by removing the back cover and installing new side seals. When the back cover is off, you can look over the ring and pinion. Order the rear differential mount and replace it at the same time. Check that the side flanges on the dif. are the same as the ones in your car. The ones on the 3.23 I put in had a different bolt pattern for the half shafts. The flanges pop out as they have a spring ring that index them. Be careful with the thin metal dust covers on the axle flanges. They can be bent and then rub on the dif. case.
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Old 09-26-2013, 02:11 PM   #9
Kubica
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Originally Posted by motorhead55 View Post
I really don't feel I lost much in acceleration.
AGAIN, I appreciate the recommendations I have got here from the forum.
Trust me, you lost quite a bit of acceleration (I went from 3.23 to 3.46).
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Old 09-26-2013, 02:12 PM   #10
Kubica
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This might actually be the slowest e46 in the whole country. Automatic xit with 3.23 gears....
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Old 09-26-2013, 07:52 PM   #11
motorhead55
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Originally Posted by Kubica View Post
This might actually be the slowest e46 in the whole country. Automatic xit with 3.23 gears....
I'm not an automatic, 5 speed stick and 3 pedals. The 3.23 ratio was factory STOCK in a 325xi and 325xit with 5 speed stick.

Last edited by motorhead55; 09-26-2013 at 07:54 PM.
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Old 09-27-2013, 07:18 PM   #12
motorhead55
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Drove the car today on a 40 mile trip with a good 2.5 mile grade coming home. It is had to believe that just 220 rpm lower makes a difference but it sure did. My car is quieter and feels comfortable at 70-75 mph now. Taching just over 3,000 rpm at 70. The Cuesta grade is just north of San Luis Obispo on the 101 north. It is a formidable 2.5 mile grade. I have driven it for 35 years in personal car and UPS trucks. It separates the clunkers from good cars as I have seen MANY broken down cars on the up hill side. Before the change, my car ran the grade like flat road. I do feel the difference of gearing but the car still pulls the grade easily in 5th gear. Good suggestion from the forum.
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