0A3 gearboxes with type 3 c-diff

[goodall]

Ive been looking to change the gearbox in my 90 Quattro for a while now, it has a 2.5tdi fitted and then 7As' ratios aren't suitable, 2800rpm at 60

I have looked at 01E gearboxes and this is a known route and will bolt in. However for a little more work I really would be interested in the 0A3 with a the 40:60 C-diff. There is a scant information online about these gearboxes. It seems 2006 onwards they had the type C

However other than the RS4 box they don't have a 4.11 ratio but I was thinking off building my rear with 3.889

[Error404]

I've got B7 RS4 box in my coupe.
The ratios are short, probably not much longer than the 7A actually.
I am not sure which boxes got the T3 torsen or when, other than all the B7 RS4s had them. I believe that the B7 S4 did, and is 3.889. They are rare though so finding a box might be a struggle. The 2.5TDi and 3.0tdi quattros also had the 0A3, again not sure which used the T3 torsen. They are mostly 3.889, there is an oddball 3.700 also.

[goodall]

Yes looking at the ratios the RS4 wouldent have suitable ratios. There's actually one of the boxs with the 3.7 ratio on eBay for about half the money of any other 0A3

How does the coupe drive with the 40:60 split? You have a torsen on the rear axle too ISTR? Which is so thing I currently have

I guess if I had an up to date version etka it would be easy to cross reference the RS4 C diff

[Error404]

3.7 final drive you are going to have problems finding a rear diff to suit.
I would say even the S4 ratios will be too short for your low revs off the TDi.
I've been looking out for a JMG box off a 3.0TDi for another project, was going to try and see it its possible to fit 3rd, 4th, 5th & 6th into a 4.11 RS4 box.
The 3.0TDi quattro boxes seem rare and people ask strong money for them.

Driving wise the 0A3 is far nicer than the 01E, the syncros are so much smoother and it makes the car feel far more modern. T3 centre diff coupled to the Torsen rear diff it drives more like a RWD car but with much more traction, still goes sideways in 3rd in the wet. Fun.

There should be details on everything you need to know about fitting in my project thread

[goodall]

The JMG is my preference as seems have ideal ratios and the final drive is 3.889 which can be got from a V6 coupe so I'm hopeful, price is rather high but my fuel saving working of BSFC data should be around £800 a year so it'll pay for itself, eventually thanks to lowering the revs.

I like the sound of the handling, with the Diesel engine I know seems odd focus on handling so strongly but I'm planning on running close to 300hp and 650nm
The 01A is likely at its limit running current power and torque

[Error404]

Yup, I'd recommend going to the effort of doing the converison. Actually, it is a cheaper conversion than finding the relevant 01E mounts & linkage. Plus most 01Es are shagged these days.

[goodall]

Unfortunately checking the P/N for the centre diff in the various boxes and seems its just the S4 (HVM, JMF) and RS4 (HLD, JMH) got '0A3409751J' which is the type 3 torsen

[Error404]

Where did you get that info? Mine is an HLD box, also RS4. I've also seen a self study document which detailed the OA3 with T3 TORsen used in the A6

[goodall]

I don't have ETKA thats far enough up to date, however using www.partscats.info I checked the PN for the RS4 C-diff and then looked see where else could find it, also searched RS4 C-diff PN and jimellis came up same result S4 and RS4

The other 06-08 gearbox codes all seem to use 0A3409751B which is used in the 0A3 pre 06 boxes as well

I wonder which A6 the type 3 was used in, from looking on that partscats.info site the 0A3 seems use the regular torsen as used int he rest.

From what I understand Audi had a lot marketing put out at a point which said quattro was 40:60 but later this was retracted, but I doubt that would be the case with the self study as they are technical documents produced by Engineering

[goodall]

Checking out prices, thinking best step to take is buy a rs4 gearbox and fit it as they are about 1/3 the price and work with current rear diff ratio, then when a cheap tdi is available buy it and fit with a 3.889 rear diff and fit the torsen from the rs4 box onto the tdi box. My worry is could end up getting very expensive if I go buy all the parts at once.

Future engine modifications require a stronger box fuel savings from better ratios isn't as important right now

[andy10v]

Checking out prices, thinking best step to take is buy a rs4 gearbox and fit it as they are about 1/3 the price and work with current rear diff ratio, then when a cheap tdi is available buy it and fit with a 3.889 rear diff and fit the torsen from the rs4 box onto the tdi box. My worry is could end up getting very expensive if I go buy all the parts at once.

Future engine modifications require a stronger box fuel savings from better ratios isn't as important right now

Good man, the answer is always more power

Do you have a build thread? Sounds like an interesting car.

[goodall]

I don't have a build thread, I keep meaning to start one, I've even taken pictures 3 or 4 times to do it. I built it thinking 7A power would be plenty, then I wanted stock S2 power, now I want stock RS2 power, from a diesel... Ill start a build thread this weekend perhaps


But back to the 0A3, got on ETKA thats uptodate to 2012, only two diffs used in the 0A3, the *J diff seems be the type 3 worsen used in the RS4 and S4 only, the *B is used everywhere else and theres no other letter extension used on the parent part number for the dfff

On eBay theres a rs4 box for with prop and shifter for less than a 01E with 3 times the miles. couple laser cut plates in work and some shafts I could get this working I think