I want to replace my E36 3.45 Diff w/E30 2.93 for highway speeds, less road noise

[dharrell]

Dear BMW gods:

I want to swap the E30 2.93 differential from a 1986 325e into my 1994 318ic, replacing the 3.45. I am on the freeway a lot and I am more concerned about eliminating some road noise, improving gas mileage and getting higher speed (i.e. 75mph) with a lower RPM. The tire size I currently use are 205/45/17.

Should I switch to 215/45/17 or 50 series?
Has anyone performed this successfully?
Do I replace ALL the flanges (sides and front) from the E36 to the E30 and what kind of MPH can I expect at 3200 RPM with the new differential?

I am in Texas, it's a big state and I don't own an airplane or have a pilots license. I will be going back and forth to Southern California again for business, so as you can see, I drive the freeways.....a lot.

FYI, I used to own an 86 325e 5-speed and know first hand that when I drove it, it literally flew the freeways of West Texas over 90 mph with barely a strain on the engine. I would like the 318 to fly as well, but the lowest ratio I could find for E36 was 3.15 that are in the 325's and I dont think that will work considering the 1:1 ratio on the 5th gear. Thanks in advance for your help.

[epmedia]

No, I'm not a Bimmer God,
I would just see if the 215's would fit the car... Beauty of a car btw.

I went from 205s to 215s on my '78 and it dropped the rpms a few hundred on the freeway. A 1.1 ratio 5 speed? Those are hot items for the e21s.

I don't know about the diffs, somebody will chime in though. Robert

[ponchiz318]

Originally Posted by dharrell

Dear BMW gods:

I want to swap the E30 2.93 differential from a 1986 325e into my 1994 318ic, replacing the 3.45. I am on the freeway a lot and I am more concerned about eliminating some road noise, improving gas mileage and getting higher speed (i.e. 75mph) with a lower RPM. The tire size I currently use are 205/45/17.

Should I switch to 215/45/17 or 50 series?
Has anyone performed this successfully?
Do I replace ALL the flanges (sides and front) from the E36 to the E30 and what kind of MPH can I expect at 3200 RPM with the new differential?

I am in Texas, it's a big state and I don't own an airplane or have a pilots license. I will be going back and forth to Southern California again for business, so as you can see, I drive the freeways.....a lot.

FYI, I used to own an 86 325e 5-speed and know first hand that when I drove it, it literally flew the freeways of West Texas over 90 mph with barely a strain on the engine. I would like the 318 to fly as well, but the lowest ratio I could find for E36 was 3.15 that are in the 325's and I dont think that will work considering the 1:1 ratio on the 5th gear. Thanks in advance for your help.

I can't answer your question but looking at your car......... I think I passed you up on 45 heading south past 610 north(heading towards downtown) a couple of days ago. I also have a black e36 vert but my tail lights are blacked out and I have M6 replicas......

[IAMMAGNUS]

I want to swap the E30 2.93 differential from a 1986 325e into my 1994 318ic, replacing the 3.45. I am on the freeway a lot and I am more concerned about eliminating some road noise, improving gas mileage and getting higher speed

i was under the impression that you couldnt swap in a e30 diff into a e36 at all you could only do that in a Ti/z3 which of course already has the e30 based rear end. I could certainly be wrong this is more of a question than a statement..........................?

[Reuffeo]

^^^ i also believe I have heard that. you could just go with the 2.93 open diff that is made for e36s already. its considerably lower than what running already and it should improve your mpgs a bit more.

[Bluebimma]

Im positive you can NOT use an e30 differential in a non-ti/z3 chassis.