3.73 stuffed in yesterday

[Jeff N.]

The diffy unexectedly arrived friday PM on the door with a "thud" and ding-dong from UPS. Had the parts and Martin (as usual) would rather work on cars than talk about them. (thanks).

Upon inspection of the unit, turns out that the pinion flange was a perfect match for the driveshaft and no flange swap was required. For the record, this donor car was a 89 525i stick and it's a perfect match to the d/s of a 90 535i stick.

Took about 3 or 4 hours to swap the unit over. That included cleanup of the donor unit, a little under car cleanup and the installation of new halfshaft axle seals. No need to drop the exhaust (thank goodness). Another installation note is that you need to use the existing outer drive flanges to match to the 535i halfshafts; the ones from the 525 won't work. Of course, this is simple as you just pop them out of the old diff and plug them into the new unit.

Health of the new diffy seems good. Very quiet and the lockup seems tight. Less lash than the older higher mileage (3.46 LSD) unit to boot.

Driving impressions are good. Car has more snap off the line and accelerates noticably better. Not a huge difference but it's nice. Maybe not so nice is the freeway RPM hit. At 70 MPH, engine now spins about 2700 RPM or so in 5th. This is definately not a swap if you do a lot of highway driving.

BTW, no need to recalibate the speedo it seems. Did a 1 mile / 60 MPH test and it's spot on a 60 seconds.

For the $200 or so invested (yup, got a deal it seems), this is a pretty nice little swap over.

Should be interesting as the 3.7 engine comes together; could be too short for that sort of power.

Cheers!

Jeff

[bahnstormer]

not a huge difference?
jeff, maybe our butts are calibrated differently
but my 3.64 made a huge presence for me
enjoy!

[Robin-535im]

T
Health of the new diffy seems good. Very quiet and the lockup seems tight.

Glad to see you got some car time this weekend. Which reminds me, I have to talk to BMA today...

How does one test the lockup? Just floor it and check the skids? I've been wondering lately if the LSD mechanism gets worn out and how you would know.

Any news on the 3.7?

[Jeff N.]

How does one test the lockup? Just floor it and check the skids? I've been wondering lately if the LSD mechanism gets worn out and how you would know.

haha...did a very scientific test - goosed it in Martin's gravel driveway. The last unit would leave sort of a left-right-left mark as the wheels would grab and release. This one leaves two smooth patches. I'm assuming this means it's better!

3.7 is a go - full SWMO approval and budget ready. Just need to make some time to get into it. Gonna have it built locally. First step will be to strip down the block in the garage and have it dipped and checked out.

[Robin-535im]

Ohhh yeahhh - nice new 3.7L, new diff, you're gonna need staggered tires to hold that beast down!

Don't toss your old block yet - still have dreams of putting it back in it's original chassis... assuming you aren't going to build that one into something even bigger that is. Or donate it to Martin's "now relatively slow" 535.

[Bill R.]

haha...did a very scientific test - goosed it in Martin's gravel driveway. The last unit would leave sort of a left-right-left mark as the wheels would grab and release. This one leaves two smooth patches. I'm assuming this means it's better!

3.7 is a go - full SWMO approval and budget ready. Just need to make some time to get into it. Gonna have it built locally. First step will be to strip down the block in the garage and have it dipped and checked out.

a

[Jeff N.]

(Note new FCC compliance ala the Superbowl)

He's done a really good job of getting a balanced setup. The much broader torque curve of the stock motor combined with the 3.64 and the 14lb lb flywheel really make it feel strong.

My car is too peaky. Significantly less torque off cam really hurts the overall performance. Feels like a poorly setup turbo...lag lag lag...ohh...3.8k RPMs...vrroooooooom!

As it is now; Martin's car is quite a bit faster than mine and much more driveable. With the new 3.73, I could maybe be faster or as fast in a straightline drag race where I can keep the car on cam. I'll get crushed in a road race where my car goes off cam while his is in the fat part of the torque curve.

I think my choices are pretty simple now - either dump the cam or go for a bottom end that works with the cam. Sooo...why think small when you can just get in deeper?!

Cheers!

Jeff

[Bill R.]

1

(Note new FCC compliance ala the Superbowl)

He's done a really good job of getting a balanced setup. The much broader torque curve of the stock motor combined with the 3.64 and the 14lb lb flywheel really make it feel strong.

My car is too peaky. Significantly less torque off cam really hurts the overall performance. Feels like a poorly setup turbo...lag lag lag...ohh...3.8k RPMs...vrroooooooom!

As it is now; Martin's car is quite a bit faster than mine and much more driveable. With the new 3.73, I could maybe be faster or as fast in a straightline drag race where I can keep the car on cam. I'll get crushed in a road race where my car goes off cam while his is in the fat part of the torque curve. 1

I think my choices are pretty simple now - either dump the cam or go for a bottom end that works with the cam. Sooo...why think small when you can just get in deeper?!

Cheers!

Jeff

[Martin in Bellevue]

With the new 3.73, I could maybe be faster or as fast in a straightline drag race where I can keep the car on cam. Jeff

wow.

[Jeff N.]

Huffer? That a Turbo? Never heard of a huffer...