Been running 4.56s' in my A4 for 4 1/2 years. 1st & 2nd gear were wild,throttle response was immediate even with convertors(TCI 2800 & Yank SS 3600) as accelation occurred while the convertors were flashing up. Gas mileage was good,21.5 mpg (for reference,the OEM 3.23s gave 24.5 mpg under identical conditions) at freeway legal speeds (2500 rpm @ 60 mph & 3000 rpm @ 72 mph),even took 5 trips to Florida from northern Ohio.
Back in Oct.2003 on the way to Englishtown N.J. for SLP Aprreciation Day,developed a noise in rearend. Being that I've been doing rears since the 60s',the noise sounded like a passenger side carrier bearing,which eventually proved to be the case. The noise/growl never worsened.
here's the passenger side carrier bearing with 30,000 miles on it since it started to 'growl'.
4 years later the OEM rear was replaced with a rear containing 4.56s'. I had a housing with axles that I had picked up at a Canton Ohio swap meet,picked up a new Eaton posi at Summit from their 'demo/returned' corner for $200 (it was missing the spider center shaft,since I had a few-no problem). Had gearsets of every ratio for the GM 7.5/7.625 rear and decided why not go all the way with the 4.56s' (used Richmonds that I found for $25 at Canfield Ohio swap meet).Cleaned that housing and POR15'd it,used new bearings,set the pattern for a good centralized swipe and ended up at .006" lash. Had some 'noise' but I wasn't expecting quiet with a used gearset.
3.23 rear out,4.56 ready to go in
Periodically looked at the wear pattern and it improved with mileage.Ran the rear for 4 1/2 years and 41,000 miles with no problems. I will probably miss those 4.56s'.
Rebuilt(cleaned,POR15'd,drilled & tapped a drain hole in the bottom) the OEM rear using everything from it except for bearings,seals,and a set of backing plates I had. Lash ended up at .0035" (a little tighter than what it should be) to get a good pattern.
The homemade/fabricated case speader worked well. built-fabbed a case spreader
4.56 rear out,3.23 ready to go in
Been running it for a week now and still quiet. I'll pull the cover tomorrow and see how the contact pattern is doing.
The 4.56 rearend will stay intact as it's usable. Another housing I have will probably be built with 2.73s',or 3.73s'.