Diff needed

#1

Anybody have a known good 3.73 lsd? Trying to get one from diffsonline.com but I think he’s out of town. Need one for RA this month.

#2

we sell rebuilt 3.73 lsd differentials. they are 800 with core exchange. I can have one out to you in a week or so

Drive-gear.com

#3

U have one at 65ish lbs breakaway?

#4

Yes, get a diff that stout so your car can understeer like a pig at turn-entry. That’ll make life easier on me at Barber next year.

Oh by the way, I did confirm that SE is coming to Barber again next year. Woohoo!

#5

So what should I get? Mine at 40 lbs spins some serious inside wheel. T7 and 10b at RA are like gravel to me. And +1 for Barber.

#6

You don’t want a diff any stronger than is necessary because it makes the rear wheels not want to spin at different rates, therefore understeer. Prob no stronger than 50ftlbs. Mine is only barely stronger than yours, and I don’t get rear wheel spin.

A number of things can cause rear wheel spin so it’s a mistake to focus only on the diff. Fred Switzer’s diff is stronger than mine but he has serious rear wheel spin problems.

Things to check.
Don’t have too much camber in the rear. More than -2.5 in the rear is too much. It’s especially too much on your inside tire. The rear gains camber in compression. It’s the front where you want lots of camber.

Don’t have your rear sway too tight. If you have to tolerate a bit of understeer to keep your rear end planted exiting slow turns, it might be worth doing.

Check your corner weights. With your sways disconnected.

Maybe tired shocks. I dunno, I don’t know enough about shocks.

Try playing with rear tire pressure. More air creates a more rounded tire profile for the camber challenged. Less air creates a more square profile for not camber challenged.

Don’t assume this is gospel. You’ll find folks that disagree with everything I said. This is racing. There isn’t consensus that the sun will rise in the morning.

40ftlbs is a little on the weak side mind you, but only barely. I measured my diff yesterday. With my fancy digital torque wrench I got 37ftlbs. With my old school beam torque wrench I got 44ftlbs. The beam wrench is probably the accurate one.

#7

Bought 2 complete cars yesterday.

One 2dr 325ix and the other 4dr 325i.
Know for sure ix is 3.73 but don’t know breakaway.

Will pick up tomorrow

#8

Thanks reb but ordered one from drive-gear this morning.

#9

Sorry to hijack this thread but I think I’m up for diff as well. Here is the deal… bought the car last year and when I first test the car the rear diff was extremely noisy I was told that’s normal … didn’t know anything that time about the car… so I did bunch of DE at VIR … and by the end of the year I start wearing stuff… both front hubs, links, coil pack and distributor cap and rotor … well also I noticed that especially around turn one I was putting lot’s of smoke so first I taught I was sliding but in the real world it was “one tire fire” I was told that probably my diff is shot and it’s acting like open diff instead LSD so now what should I do… buy used one or get re-built one.

PS: Drove several cars after and none of the sound like mine they are actually pretty quite

#10

Drive-gear.com. Ask for Andrew. He’s probably lurking here anyway.

#11

While you’re at it get a rebuilt trans from him too.

#12

Yeah I think that what will happened anyway except transmission will have to wait… first I need to make some cash :frowning: Hopefully it will hold up … right now it’s just leaking little bit through the seal.