3.46 Differential

[Ron Stygar]

Differential #4 on the way. Looks like this one might make it.


<img src="http://www.unofficialbmw.com/images/differentialno4.jpg">

[Polar Bear]

hope this one makes it -

question, which would be a better upgrade - 6 speed transmission or rear differential swap?

[Randy Forbes]

Keep your fingers crossed...

With any luck, you'll have have it in the car before HC02.

I've been getting a chance to drive mine around lately, awesome pulling power (with 3.73:1 in an 01 M Rdstr).

[dakarm]

Originally posted by Polar Bear
hope this one makes it -

question, which would be a better upgrade - 6 speed transmission or rear differential swap?


rear diff is often refered to as poor mans supercharger :)
provided you go the right direction :)


i think as far as cost goes diff swap is the way to go.

[chazzy]

Is there anything actually glass in there? Or is it just a preventative measure?

If this works out (affordably), I know my next upgrade!

[Ron Stygar]

Didn't do anything for first three.

[5 Rakete]

How many are left on the planet now? Weren't there just 8?

[karlblomquist]

For no particular reason except lack of patience I opted for a re-build of my existing final drive rather than waiting for a replacement 3.46 version. I don't anticipate ever wanting to return to the 3.15, so having two complete assemblies was not important to me.

I sent it to Jim Rowe (MetricMechanic.com) to have the following modifications done:

1. Swap r/p from 3.15 to 3.46

2. Modify LSD mechanism from 25% fixed LS to %20-100 variable LS.

3. Add additional clutch plate to LS assembly - rendering the life of the whole assembly likely longer than the car. ;)

He does this for just around the same cost as a replacement final drive assembly. You can get just the r/p swap for much less than the cost of a replacement assembly.

Total turnaround time was < 1 week. It's on its way back now so I should have it back in next week sometime. I'll provide my impressions then - although I may wait for a bit to install because I also have Supersprint DTMs on the way. Makes more sense to re-install everything at one time.

Cheers, Karl

[dakarm]

Originally posted by karlblomquist
For no particular reason except lack of patience I opted for a re-build of my existing final drive rather than waiting for a replacement 3.46 version. I don't anticipate ever wanting to return to the 3.15, so having two complete assemblies was not important to me.

I sent it to Jim Rowe (MetricMechanic.com) to have the following modifications done:

1. Swap r/p from 3.15 to 3.46

2. Modify LSD mechanism from 25% fixed LS to %20-100 variable LS.

3. Add additional clutch plate to LS assembly - rendering the life of the whole assembly likely longer than the car. ;)

He does this for just around the same cost as a replacement final drive assembly. You can get just the r/p swap for much less than the cost of a replacement assembly.

Total turnaround time was < 1 week. It's on its way back now so I should have it back in next week sometime. I'll provide my impressions then - although I may wait for a bit to install because I also have Supersprint DTMs on the way. Makes more sense to re-install everything at one time.

Cheers, Karl

Do you have a break down on cost for each step?

thanks in advance.

[karlblomquist]

Originally posted by dakarm


Do you have a break down on cost for each step?

thanks in advance.

$1095 for the rebuild work and associated re/re components (shims, crush sleeve, etc.).

$350 for replacement r/p gears (he keep originals for re-use somewhere else potentially).

This would give you a $1445 price tag for getting the unit to a 3.46 diff ratio.

At this point if you can find a set of 3.46 gears you could probably find someone else to rebuild for less, but it was the total package (see below) and the comfort level in Jim's expertise that I was after.

Add $250 for modifying LS to a Variable Limited slip. I first learned about this over in the E39 group from someone that had it done to an M5 LSD assembly and installed it on their 540i.

Add $250 for extra clutch plate to thicken up the clutch. Jim said that if you don't drive the car hard this is not really a necessary addition, but if you tend to drive hard sometimes and want to be guaranteed that LS clutch wear will be the last thing you need to worry about, then it can be a useful add-on. I figured, what-the-hey, I'm already at $1695, so what's another $250? :yikes:

Jim did give me a bit of a price break on the whole deal - I'm in Canada and the dollar difference kills us when dealing with U.S. merchants. He was nice enough to "sympathize" and cut me a little break in the end.:)

If you call him, allocate some time, he loves to talk shop!

--
Cheers, Karl