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I was wandering if the front axles (left and right) for a 1990 Audi V8 3.6 Automatic with UFO brakes are identical to the ones on a 1992 V8 3.6 automatic equiped with the Girling dual piston caliper and the different strut assembly. Also, do you think I should worry and replace a rear Thorsen differential that has been mildly rumbling for the past two years (fluid level OK, changed to synthetic 75-90)? I have the opportunity to get a used rear differential for about $50.
Cheers,
Florin

Hi Florin,

there has been a difference, but I don´t know exactly the date. It should be around model year 1992. Somewhere in this Forum there is the exact Info; I´ll have a look.

If you can get the differential for 50 Bucks: Do it anyway!

For better explanation I added a sketch from the parts catalogue. Is it that what you mean?

Hi again,

the difference starts from model year 1991 and assembly number 4CNN004001.

Do you mean these calpers (attachment)?

Hi Berthold,
Thank you for the prompt and exact answer. I called Audi dealership and the gentlemen that I spoke with confirmed that the axels are indeed different. The picture that you sent me shows the new (after 1991) calipers and unfortunately my car is equiped with the old ATE (UFO) brake rotors with different calipers. I should follow your advise and get the Thorsen differential but unfortunately I would have to remove it myself from the other car, a job that might be too much for me.
Another question: Audi used to retrofit the V8's ATE front rotors and strut assembly for clients that were not happy with that set-up. Would they do it after so many years or did they do that only for the warranty period?
Thanks again,
Florin

All V8s sold anywhere in the world left the factory equipped with the UFO brakes until the very end of that model. Absolutely no exceptions. For model year 1992, there were indeed made some changes to the front suspension components (mainly to be able to use the same parts as on the then new C4) but the UFO brakes remained on the car.
The Girling G60 brake from the substantially lighter and less powerful 10V Audi 100/200 you are referring to used to be dealer-retrofitted (with factory backing) as an "emergency quick fix" to some 1990 cars in the North American markets (US/Canada) when and after owners complained about warping (and repeated rotor changes did not fix the issue) ONLY. This conversion was done solely to pacify select angry customers who otherwise would have dumped their $50k cars and shopped elsewhere, leaving Audi with another PR disaster just after the corporate image barely recovered from the 'unintended acceleration' media nightmare and tried to tap into the big-prestige market for the first time.
Audi stopped doing this at some time in 1991 anyway. If you´d ask for this today, they tell you “no”.
The G60 brake you are talking about is absolutely inadequate and totally overburdened by the power and weight of the V8 except maybe for the most sedate driving styles and environments - spirited driving is a no-no as is mountain driving...Remember, we`re talking about a two-ton car that goes 159 mph (257 km/h) - at least that`s what my 4.2 is capable of
(European) V8 owners dissatisfied with the replacement cost and performance of the UFO brakes today mostly convert to the "HP2" front brake setup found in the V8-powered "C4" S4 and the later S6 (1992-1996) as well as the D2 A8. If you are in the US, the strut/brake assembly from a 1995/96 S6 would fit right in.
In Europe, used components for this HP2 conversion are plentiful and cheap to come by; replacement rotors cost only a fraction of the UFO parts and every parts store carries them; warping is no longer an issue even on the track and fade resistance is improved somewhat compared to the UFOs. And when opting for the smaller of the two available sizes (there are 314 and 322 mm diameter versions around, the latter being used in the S8 or the S6+) you can retain the stock wheels.

Interesting to hear that all V8s came out with the UFO brakes, thanks. My 1990 V8 performs adequately with the UFOs and I'll stay with them. Your observations about the G60 brakes are correct but I've seen one retrofitted car here in Canada where I live.I would be curious to know if they had to use different front axels with the G60 retrofitted brakes.
Thank you.

The 1992 and later Audi V8 and Audi S4 used the dual piston G60 calipers and Audi discontinued the use of these UFO brakes.
SJM Autotechnik. Any comments?

Hello again,

seems to be a neverending story with the brakes (and some more like: which oil to use).

This is not the complete truth, as B. Homburg wrote.

Only D1 (D11) cars in Canada and the US were fitted with th G60 calipers. All others were fitted with the UFOs. The Ufos were the standard brakes in all D1 (D11) cars and the C4/S4 for quite some time. Audi discontinued them `95 or in some models even later.

Anyway, I think the UFOs aren´t so bad as some comments may make them: they last very long and the performance is very good (with good brakepads). You only have to take a bit more care concerning cleanlyness and avoid multiple extreme brakings from mid to high speed.

That information on the SJM website is incorrect.
He got it from the "1992 Model Change Information" dealer training booklet, though. So don't blame it on him but on AoA...

to repeat: NO V8 sold ANYWHERE in the world was delivered from the factory with anything else than with the UFO brakes. Period.

Audi V8 brakes had no issues with mine infact there the best brakes i ever come accross in my previous cars i have owned.