Center Diff Question

B6/7 S4/RS4
#1

I am planning on getting the 4:1 center diff from JHM here in the next month or so. I was thinking of finding a center diff to send in for modification so 1) I didn’t pay the core charge, and 2) car wasn’t sitting while I waited for the diff to get finished when I sent it in.

I stopped at a friend’s german car shop and they just replaced a transmission in an RS4. The guy destroyed the syncro’s from what they told me so the diff should be in good shape. I looked at the tag on the trans and saw it said 0A3.

So I wanted to know is the RS4 0A3 trans/center diff the same as the 0A3 trans/center diff the same in my '04 S4? If it is, then hes going to let me have it to send out for the modification and then he’ll take my center diff once its taken out

#2

Sorry to pop in without an answer, but just so you know, from what I’ve heard, JHM upgrades and ships your diff out normally the same day they receive it. So your car wouldn’t be down that long. I understand though if you can’t have it down for more than a day.

#3

The RS4 center diff is already a 4:1 so just swap the one from your car with the one from the trans that came out of the RS4.

#4

The unfortunate part for me is ground shipping is 4 days each way. The bummer of living on opposite coasts. I don’t have a good place for my car to sit at my shop since we are getting ready for summer and I wouldn’t want to take away a lift from him with how busy his business is.

I wasn’t planning on buying another diff to send out since I might as well just pay core charge at that point. Just the ease of being able to swap diffs from the 2 transmissions would be nice.

#5

Well this already makes it easier.

#6

I ended up getting the entire RS4 trans from my buddy since its just been sitting in his shop, so any idea of what it would be worth? Supposedly it was crunching into gear, and I just took the center diff out of it. Other than that I have no idea about the transmission

Are they the same 0A3 as the s4? Would it be worth rebuilding with JHM’s kit?

#7

The center diff in the RS4 trans (and 06+ S4 IIRC) is a T3 (already 4:1) vs. the T2 (2:1) in the <05.5 S4 and A4s. IMO, the T3 has a bit smoother response than the modded T2.

As for using the RS4 trans in your S4, that’s a no-go unless you plan on swapping the ring/pinion on the front diff (4.11 vs. 3.89) or swapping in a rear diff from an RS4 (or A4 3.0). I’m kinda surprised an S4 guy hasn’t done this yet just to see if the gearing difference will make a notable E.T. improvement… I think the upper gear ratios are different between the two transmissions as well, but don’t quote me on that one.

Where are you located? I might be interested in the RS4 trans & the T2 center diff depending on price.

#8

[quote=“koolade9,post:7,topic:7250”]
The only reason I got it was because I wanted the diff out of it once I learned it was 4:1 and he is tired of it sitting in his shop. Im located in Cleveland OH. I figure it will be more useful to someone else as I don’t see myself going through trying to swap it in.