My 91 325i track car

[5Toes]

how does the car ride with bilstein black touring and the HR race?

[kts]

how does the car ride with bilstein black touring and the HR race?

Car is on yellow Bilstein sports. The black part you see is a dust cover for the rear shocks.

On the Bilstein sports + HR race I think the car rides great. I came from the Subaru world where I had a limited Subaru spec suspension a Japanese only model (Spec-C Type-RA) which was SUPER stiff (Called the kidney buster by some friends) and then a set of ASTs on my next Subaru which rode a ton better but IMHO the Bilstein sports + HR Races ride a lot better for driving around the terrible roads in DC and for weekend fun.

[kts]

How I spent my Sunday night:

Step 1, remove a perfectly good stock bushing out of the Z3M diff cover



Step 2, remove the rear diff.



Step 2.5, mutter expletives as the rear half of the driveshaft comes along for the ride.

Step 3, put on work table and figure out how to separate the DS from the diff since it's frozen.



Step 4, look at the tab and discover you have a 2.93 LSD vs the 3.73 LSD you thought you had.



Step 5, ponder the meaning of life and if you want to reseal this 2.93 LSD and keep using it or look for a 3.73 LSD

Step 5.5, wish you knew more about diff ratios and what the best options for a track car would be.

Step 5.75, think that acquiring a 3.73 is probably the better way to go vs the 2.93 but you're not sure

Step 6, drink a beer

Step 7, post about it on the internet.

So yea this all happened. Time to figure out what's next.

[Reub_e30]

3.73 do it

[AwakenNoMore]

Having driven 3.73 vs 2.93 back to back its a huge difference. Get a 4.10 if you want retarded levels of giggle and no top end.

[iwantspeed]

Throw the boring diff back in the car so the car is drive able until you get a proper diff sourced and resealed.

[kts]

Thanks for the input everyone. The 3.73 was the way I was leaning, it's also the diff used for Spec E30 so makes the most sense for the track.

Throw the boring diff back in the car so the car is drive able until you get a proper diff sourced and resealed.

Fortunately it's not my daily so it can be up on jack stands for a while. A local guy parts out a lot of E30s so getting my hands on a 3.73 LSD shouldn't be too bad.

[iwantspeed]

It's kinda weird for your 325i to have a 2.93 diff.

Since its out of the car you can rotate the driveshaft and count the rotations of the output shaft. And figure out if it really rotates almost 3 full turns. Or if it almost rotates 4 full turns.

Don't trust just that diff tag.

[kts]

It's kinda weird for your 325i to have a 2.93 diff.

Since its out of the car you can rotate the driveshaft and count the rotations of the output shaft. And figure out if it really rotates almost 3 full turns. Or if it almost rotates 4 full turns.

Don't trust just that diff tag.

Yea I was really surprised to see that diff tag too. I do plan to rotate and count the rotations to verify what it is.

The previous owner did a lot of work to it, he may have swapped it in and forgot to mention it or any one of the previous 5-6 owners may have done it too for whatever reason.

An instructor a while back did mention he thought my car felt slower/was "down on power" from what he remembered his old Spec E30 car feeling like, maybe that was due to the different ratios during acceleration? Or maybe that's just because I'm a slow driver. ;)

[kts]

New 3.73 diff is here.





I have no idea what I'm doing...

There was some crud of dirt/grease/oil on the outside of the rear diff around the output flanges and I already had replacement seals so let's get to replacing them.











Old output flanges had some surface rust on them so swapped the out for the ones that were on my old diff. (I'll clean up the rusty ones later on.)





Painted the diff because ooooh shiny.



Looks good to me.


And time for the Z3M cover.


Work, 2nd job, and prepping for #2's arrival has limited my time to 30 minutes here, 30 minutes there to work on the diff. I have a good part of Saturday coming up to get the rear driveshaft and diff back in the car so I can take it for a spin again.

[iwantspeed]

I'm drooling over that diff cover
One tip is to mark the top of the diff with white out.

Date
Ring and pinon Ratio
Mileage
Lsd or open

That way if there is a next owner down the road they know what's in there

[kts]

I'm drooling over that diff cover
One tip is to mark the top of the diff with white out.

Date
Ring and pinon Ratio
Mileage
Lsd or open

That way if there is a next owner down the road they know what's in there

Yea I have been drooling over the diff cover for a while since it's been in the pile of parts I'll install "one day". I looked up records and I bought it in December 2011! I should have bought a few more as investments, I paid $120-150 less then vendors want for them these days.

That's a good idea on the diff. This has the tag with it and I covered over the "S" painted on so that's still there but the other info would be good for when I forget a few years from now. ;)

[kts]

Finally got the diff back in. This was a few weeks back but just getting to it now since my son was born on 9/3/16 and everything has been a blur the last few weeks. :)



HOLY CRAP the car pulls with the 3.73. Man that's fun. I fully expect to rack up a number of speeding/speed camera tickets soon.

I had to pick up a new battery since my car was sitting for so long I managed to kill yet another battery. When I first started the back up a jump worked but after that it was dead-dead. Some research on that plus some weird electrical things before/after I jumped the car pointed to the voltage regulator being suspect. Pulling it out the old one showed one of the brushes was shorter than the other which was odd but they didn't look as bad as some others I have seen. Being a $15ish part I replaced it anyway. With the new VR and battery so far so good.

old vs new voltage regulator


Great weather in MD for a change so I'll be driving the E30 into work every day this week with a huge grin on my face. The sexiest car in my parking garage.


Also picked up an 027 M30 AFM for cheap so we'll see how that goes. I have a set of M50 injectors left over from my M50 I could throw in too but will probably splurge for some 19lb rebuilt units. I'll get some steel this week to make a bracket and debating about just a K&N cone filter + make a heat shield or buy a Kamotors intake which has everything done. If I sell some spare parts the Kamotors route is probably how I'll go to save some time. I know this mod can be pretty controversial but I'll give it a shot since why the heck not? I don't have much invested in it so far.

[iwantspeed]

CONGRATS ON THE NEW BABY


the 3.73 is a great overall diff ratio

[kts]

CONGRATS ON THE NEW BABY

Thanks! It's been a fun, if exhausting, time getting used to a newborn in the house. We have a 2 year old and even though it wasn't that long ago you quickly forget how much work a newborn is.

the 3.73 is a great overall diff ratio

I 100% agree. Can't believe how it makes the car feel, this is how the car was meant to be. Still have no idea why someone replaced it with the 2.93 but I am sooo glad I'm back to a 3.73 on there.