535, manual tranny and 3.76 and 3.91 rear ends

[Jeff N.]

I think a few of you guys (JoeS, Robin, Dave R, others?) are running either a 3.76 or a 3.91 rear end. I'm considering upgrading and am trying to decide which one I want.

I'm leaning towards the 3.76 unit as I think the 3.91 is a bit too short. Likely makes first gear pretty unusable.

Can I get some comments from you guys who are running the shorter rear ends on what you like / don't like about the ratios? Street vs. Highway, usablity of the gears, other comments...

thx!

Jeff

[632 Regal]

Jeff, what is the current stock gear?

[JAlfredPrufrock]

That's what I've been wondering.

[Scott H]

It's a noticeable improvement. I do a lot of highway driving and don't mind it at all. 80mph = ~3500rpm IIRC. Dave Rutkowski has a spreadsheet to calc that stuff, and I volunteer him to give you the rundown in each gear.

Whatever you do, don't do what Martin did.....he really missed the boat by going with a 3.64 :p

[JoeS]

It is definately short of the line, but for cruising the parking lot is just fine.
One thing for sure..... It will certainly jerk you right out to the hole. I would say that a 3.91 would be useless. I ran with my 4.27 on the manual tranny for about a month. First gear was useless, so since the difference between the gearing is about 9%, i can imagine a 3.91 being close to enjoyable.

Attached ( i think - is spread sheet for comparing RPM)
Change the txt extension to XLS, since we can not upload XLS extensions.

[Martin in Bellevue]

Jeff has driven my car with the 3.64 enough to be afraid of the 3.91 or lower gears. That 3.64 lsd trigger was pulled with the knowledge that it was from a low torque m20 in good condition; it was a good price, and it was replacing an open 3.4. It is too bad there isn't a close ratio gearbox reasonably available for the m30.

Took the fam on a weekend trip to west WA. The 535 is great on those 2 lane roads. The roll on power in 4th really shines with the maf & that 284 cam. The brake squeal seems to be gone with the Bav Auto brass caliper bushings. The front 850 calipers have Hawk hps pads.

http://www.bavauto.com/assets/imglib500/CBUK.jpg


blah blah blah...
Whatever you do, don't do what Martin did.....he really missed the boat by going with a 3.64 :p

[Jeff N.]

Jeff, what is the current stock gear?

[Scott H]

blah blah blah, brag brag brag.......brake squeal

[Martin in Bellevue]

I'm just upset because I care.


Run you bastard, RUN!!!!

[eric5150]

The brake squeal seems to be gone with the Bav Auto brass caliper bushings.

http://www.bavauto.com/assets/imglib500/CBUK.jpg

Martin, as an FYI -

I have those in my Z3 Roadster - be sure that you keep a maintenance schedule on those to keep them lubed. I had a caliper 'stick' because I got a bit too lazy with that, wore down 1 of the pads and scoured a rotor. (driver's side outer, obviously not the side with the sensor). So now I make sure to pull off the wheels, clean the guide pins/bushings and throw some hi-temp anti-sieze in those things every 3 oil changes (about 9500-10k mi).

They are great, but they are NOT a non-maintainence item.

Eric

[Martin in Bellevue]

I was surprised to see no mention of periodic maintenance in the literature. I was also surprised to see that there was no rubber boot, or some such, to keep the water & muck out.

[eric5150]

I was surprised to see no mention of periodic maintenance in the literature. I was also surprised to see that there was no rubber boot, or some such, to keep the water & muck out.

The documentation I had did mention that they require periodic greasing, but were awfully vauge about the intervals required. Since I use the EBC Green's on the front of the roadster, I get s fair amount of dust buildup. But, I'm also in SoCal, so no salt/sand/slush from roadways. The approx. 10K interval is working for me, but if you feel your brakes get squishy (fluid overheating from a dragging caliper) or you start pulling to one side, inspect/clean and re-lube - the brass bushings may be your culprit.

Eric

[gale]

I'm quite happy with the 3.91 in my e32, nearly the same as the 4.27 with the auto before I did the 5-spd conversion. Same trans as yours & maybe 300 lbs heavier.

I'm hoping to try a 3.73 in it but hasn't arrived yet (long story). Stock, your 535i 5-spd would have a 3.46 & the few e32 5-spds all had a 3.64 which would be more plentiful than finding a 3.73 lsd.

With the 3.91, 1st isn't totally useless but could stand to be a bit longer. The engine is torquey enough to start out in 2nd from a dead stop but I don't do that very often.

As for 5th, I'm turning 3342 rpm at 80 mph which is nearly identical to 3300 with the auto & the former 4.27 that was in it. The 4.27 was totally insane after the 5-spd swap, only drove it that way for a couple weeks just to get a nut. I believe e28 M5's have the 3.91, but I forget what e34 M5's have.

I'm content with the 3.91 but still am curious how it would drive with a 3.73, but not enough to jump thru hoops to get one.

[Quentin]

Aussie spec 535i manuals have a 3.64...

Q

[Brent in NZ hartge 535i]

I think a few of you guys (JoeS, Robin, Dave R, others?) are running either a 3.76 or a 3.91 rear end. I'm considering upgrading and am trying to decide which one I want.

I'm leaning towards the 3.76 unit as I think the 3.91 is a bit too short. Likely makes first gear pretty unusable.

Can I get some comments from you guys who are running the shorter rear ends on what you like / don't like about the ratios? Street vs. Highway, usablity of the gears, other comments...

thx!

Jeff

[Oldgreene34]

Jeff,

I installed the 3.73 LSD about 18 months ago and for me the compromise is perfect. More acceleration, and no problem at the top end or excess noise on the highway. You will use a little more fuel, likely because your foot will be in it more because it feels better. Now with the turbo getting closer being fully sorted I am getting slight wheel slip all the way through second gear. I know Todd goes to a higher rear end to avoid a shift on the drag strip, but for me it's all about acceleration out of corner.

My advice, put in the 3.73 and enjoy,
Dave

[Robin-535im]

The 3.91 is just fine, it's really a matter of how you're calibrated! The downside is that you tend to rev the engine higher. I love the torque, and first gear at 25 mph is about 5k RPM. I have to shift to 3rd before 60.

The M30 does fine with a 3.91 because you've got a nice fat powerband from 2k to 6k at least. I wouldn't go any higher, but I wouldn't choose to change mine either. Then again, I like to drive at the higher RPM's anyway because it just feels sooo gooood.

Coming from a stock 3.46, the 3.91 is an abrupt change, but coming from another car it's not really noticeable. I would imagine for you the choice might be what gear you can navigate track curves in best. 2nd gear can take you pretty slow then back up to almost 60 with the 3.91, but if you want to keep it in 2nd for longer without shifting you might prefer the 3.73.

So - nothing bad about 3.91, just higher revs. 3.73 might be just perfect if you're concerned the 3.91 is too big.

HTH

Robin

[Jeff N.]

Thanks everyone for the input. Likely will go for the 3:76