High Bias Center Differential Opinions
 

How does a high bias center diff affect the handling of a daily driven B5 A4? I'm not looking for random guesses or regurgitated marketing speak, I'm looking for real life experiences from people who've driven (or own) B5 A4 cars with a high bias center diff. Yes, I'm aware that Audi currently uses a high bias in their current quattro system, but those systems have changed a fair bit in the last 15 years.

Any negative effects? Specifically in low traction situations like snow or dirt. I'd like to retain as much predictability as possible in those situations, since winters here can be pretty rough.

Since I need a rebuild anyways, the option to add high bias to the diff is dirt cheap, so it's something I'm considering.

I did some reading on this topic, and from what I read, the 4:1 diff mod doesn't really have side effects when driving on lower traction surfaces.

My understanding: the 4:1 diff mod simply allows a greater amount of power to be sent to the wheels with the most traction, under the condition where the other set of wheels has less traction.

In any case I've never driven a B5 with the 4:1 mod. BUT I do have the shims to complete the mod sitting on my workbench... will probably drain the transmission fluid and pull the center diff/install shims in about a month.

Would be nice to get an account of a first-hand experience. I won't be getting a rebuild for at least 2-3 months, so I'll just wait on your impressions before making up my mind :)

I just found this out recently, but the shims you can buy tend to cause noises and binding when turning sharp at low speeds because they're a one size fits all solution that doesn't take into account different clearances due to wear. There's an online store that rebuilds them using properly size washers, either JHM or 034 I think. There was a recent thread about this probably on audizine if you want to research more.

I've thought about this recently, and I think long term, I am just going to weld the center diff. my car is getting to the point that I need to replace it sometime, and it will just turn into a racecar after that.

for you, maybe consider welding the center diff. youd lose mpg's. how many? I don't know. but it would handle a ton better in the snow.

I should maybe explain myself more: I got an Audi for the smooth, luxurious yet sporty ride. I'd like to retain as much of that quality as possible. So I guess I'm looking more for negative impressions from people who have first hand experience.

It's interesting to hear that shim kits can cause binding and noise. I hadn't heard of that before, and it's exactly the kind of thing I want to avoid.

The rebuild is necessary because the synchros have worn out. The 3rd gear synchro is especially bad, and requires me to spin up the input shaft using the 2nd gear synchro before going into 3rd, otherwise there's a high chance of grinding. I was just exploring my upgrade options at the same time.

Not really seeing the logic here. If 3rd is grinding, you'd want to double clutch and rev match best you can, matching the engine speed to the tranny speed, not the other way around.

either way, I cant say what is available for you center diff option. there are high bias diffs out there, but they are made by stasis and not cheap at all. best person to contact would be scotty at advanced automotion

Oops, my bad. I meant the intermediate shaft needs to be spun up. Rev matching doesn't work while braking.

Its tougher, but doable. And I assume this is while down shifting since you are braking.

Press clutch in. Blip throttle to slightly more revs than perfectly matched for intended down shift. Relase clutch. Brake at will. Press clutch in. Execute downshift. Release clutch or vary revs after gear is selected to match road speed

Obviously, all that happens in about .5 seconds, but you get the idea.

Right, or just get a rebuild before the synchros self-destruct and throw shrapnel through the transmission. I don't drive it like a race car on a daily basis, especially not with a 2-month old baby in the car. I like functional synchros for convenience. This isn't a Corvette, it's a 4-door station wagon.

Having said that, sometimes I wish I could do proper heal-and-toe, but the electronic throttle cut-out makes that impossible.