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Old 08-18-2019, 03:40 AM   #1
1st Gear Newbie
E46PauL's Avatar
Join Date: Sep 2010
Location: Toronto
Posts: 24
Installed 3.46 diff in 6 spd ZHP - impressions

So first off i do 90% city driving so this mod is great. Low end feels like more torque to me although i haven't launched too hard as my rear shocks are toast. On the highway at 120km im revving at around 3k which is pretty high compared to stock final drive. These numbers may be off slightly because I am running 19" rims n my speed is reading higher on Speedo when compared to what Waze is saying im doing.It's nice because im in the power band at 3k and can fly to higher speeds without downshifting. But i do wonder about the overall strain on motor since I'm cruising at way higher rpms. I believe overall I'm revving around 600rpms overall with 3.46 final drive in 6th at cruising speed

My previous diff was whining for years so this is more a must repair for me. So far I enjoy it but my boy who took the car out said he felt no difference if I didn't tell him. I'd imagine fuel economy would be worse on highway. I had to replace both fill and drain plugs and I put Royal purple 75w140 as my parts supplier said that's the fluid listed to use. Forums say 75w90 though, wondering your thoughts?

I also get an odd misfire at 4500rpms only when i floor it. The odd time at around 1800 rpms also. Almost feel fuel related. I had a running lean code previously but the car sat for over a year n code didnt return after clearing n driving over 1000kms as of late. I also notice starting the car seems a lil weaker. I replaced starter I'd say 5 years ago with oem starter. No oil leaks. Not sure how to diag this. Leaking injectors common? 04 330ci 6 speed stock on 19s 342xxx kms. I changed my plugs at 190xxx km with oem spec ngk. Hoping its not vanos related

Any input is much appreciated.

OEM Style 313
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Old 08-18-2019, 11:30 PM   #2
6th Gear Member
Join Date: Apr 2007
Location: Toronto, ON, Canada
Posts: 1,309
I have to say I never felt a higher ratio diff was needed as 1st gear is sufficiently low, even too low at times. Though I have a 3.15 diff and you had a 3.07 so you had it worse. With your 6th gear you're turning about the same RPM as me at 120kph.

I found my misfire was cleaned up by doing a carbon cleaning with Seafoam or CRC cleaner sprayed into the intake. Will clean up carbon on your intake and in the cylinder.

2002 E46 325ci // 5spd // ISC N1 Coilovers
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Old 08-22-2019, 02:35 PM   #3
3rd Gear Member
Join Date: Nov 2010
Location: T.
Posts: 491
Its a great Mod!
not sure why they didn't do that from factory other then to maintain the fuel efficiency.

that engine can handle extra 100hp without internal swaps so ... dont sweat it. enjoy your take offs!!
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Old 08-24-2019, 12:20 AM   #4
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E46PauL's Avatar
Join Date: Sep 2010
Location: Toronto
Posts: 24
Awesome reply guys thanks for the input. Will ddefinitely look into seafoam I've heard so much about it for the longest times. It's so odd taking right turns at intersections in fourth gear lol but it is fun.. I'll b doing some launches once I geet my rear shocks replaced andd this misfire sorted. If i do half throttle it seems to red freely. So odd? Jabela i scored the diff for 200 n my previous one bearings were so noisey and it leaked like a mofo so i figure it try this swap. It is alot of fun cruising at any speeds im really dying to take her sideways soon!

Can i post videos here i have one cruising in sixth at 120km?

OEM Style 313
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