Author Topic: Would 3.64 diff ruin 318is? (Read 7719 times)

josephb983 · « **on:** March 25, 2008, 05:02:19 AM »

I'm thinking I'd like my RPM's to be lower on the highway. Would the 3.64 LSD differential ruin the peppy experience of the 318is? Or would it just mean I had a longer first gear? (I wouldn't mind that). I've never swapped to a different ratio differential, so I don't know how that kind of a change feels. I currently have the 4.10 LSD.

Nick_318is · « **Reply #1 on:** March 25, 2008, 06:58:12 AM »

Having never done it I can't say for sure but you will probably loose some acceleration but you might be able to make it to 60 in 2nd gear so it might help a little, and the car might not be as peppy.

tjts1 · « **Reply #2 on:** March 25, 2008, 12:01:23 PM »

I've been driving with a 3.64 since last summer I would never go back. It doesn't ruin the car. If anything it makes it that much more fun to drive because you can beat on it for longer in first and second gear without having to shift all the time. You won't notice a drop in acceleration but you will be able to run second gear all the way to 63mph vs 55mph with 4.1. Driving on the freeway is much easier on the ears and you pick up a couple of MPGs. I'm keeping my eye out for a 3.64 lsd now. I think BMW intentionally hampered the car from the factory with the 4.1 in order to differentiate it more from the 6 cyl and justify the price difference. Nothing makes a car look slow on paper like a 2->3 shift before 60mph.

josephb983 · « **Reply #3 on:** March 25, 2008, 03:46:31 PM »

Quote from: tjts1;45440

I've been driving with a 3.64 since last summer I would never go back. It doesn't ruin the car. If anything it makes it that much more fun to drive because you can beat on it for longer in first and second gear without having to shift all the time. You won't notice a drop in acceleration but you will be able to run second gear all the way to 63mph vs 55mph with 4.1. Driving on the freeway is much easier on the ears and you pick up a couple of MPGs. I'm keeping my eye out for a 3.64 lsd now. I think BMW intentionally hampered the car from the factory with the 4.1 in order to differentiate it more from the 6 cyl and justify the price difference. Nothing makes a car look slow on paper like a 2->3 shift before 60mph.

Yeah, exactly! I was thinking that first gear is so short. And then at highway speeds the engine rev's keep making me try to shift from 4th to 5th, only to discover I'm already in 5th.

Did you do the lighter flywheel conversion on your car? I was thinking I might not need that, since the longer 1st gear might be enough. (The flywheel conversion makes 1st gear more peppy).

What car did your diff come off of? I'd be going with an LSD for sure. Have you checked into which models with 3.64 LSD fit the 318is?

tjts1 · « **Reply #4 on:** March 25, 2008, 05:52:19 PM »

My car had the ps removed and electric cooling fan. The flywheel is stock. Any e30 diff will fit your car. My small case 3.64 came from an 84 318 which is rare. You are more likely to find a medium case 3.73 from a late 325i which is very close

My 3.64 in 4th runs the same rpm as the 4.1 in 5th. Acceleration in 5th gear will feel slower than it is now but you can always downshift to 4th or even 3rd. Acceleration only matters in the first 3 gears where its not affected by this swap.

gearheadE30 · « **Reply #5 on:** March 27, 2008, 04:34:47 PM »

If you really want to shell out the bacon, the e46 330i 6-speed fits

tjts1 · « **Reply #6 on:** March 27, 2008, 08:42:18 PM »

Whats the top gear ratio on the 6 speed?

josephb983 · « **Reply #7 on:** March 27, 2008, 10:03:26 PM »

Quote from: gearheadE30;45650

If you really want to shell out the bacon, the e46 330i 6-speed fits

Which E46's had 6speed trannys in them? I thought only the ///M cars had the 6 speed? How much do these cost usually?

SpeedTheory · « **Reply #8 on:** March 27, 2008, 10:36:56 PM »

Need a custom driveshaft for that? (just curious)

Belteshazzar · « **Reply #9 on:** March 28, 2008, 08:59:07 AM »

I put a medium case 3.73 lsd in my '91. It only feels slower in 4th and 5th, and they where never "good" anyway. 1-3rd is basically the same.

gearheadE30 · « **Reply #10 on:** March 29, 2008, 04:02:27 PM »

All of the later 330i's and the ZHP had them. I'm not sure if the M3 had the same one or not. You would need to have your driveshaft cut and balanced. As for cost, they are anywhere from $900 to $2500. There's no real reason to upgrade at that price unless you need to have the tranny rebuilt anyway.

tjts1 · « **Reply #11 on:** March 29, 2008, 04:37:54 PM »

6th gear on the ZHP gear box is .85 vs our stock .81 5th so RPM on the highway will actually increase. I dont think the 6 speed ratios are apropriate for the M42 with a 4.1 rear end.

Belteshazzar · « **Reply #12 on:** March 31, 2008, 08:56:25 AM »

unless you have the e36, in which case 5th is not so tall and you start thinking about it again...

my '93 has a 3.91 in it, and 75mph is around 4k.

xsjado · « **Reply #13 on:** March 31, 2008, 10:12:45 AM »

i dunno ...IMO i sooo luv my 4.45....short but fun accelerations....and we dont have highways where i live..