B3/B4 rear diffs

[Sleeper_Avant]

been looking at s2 B3 Coupe and B4 Avant rear diffs,

am i right in thinking the rear diffs are interchangable??????

looking at the technical pics, the B4 rear diff has the cast positions for the B3 mounting positioned?

ive thaught this for a while so thaught id ask, cant find any info online except that they are not interchangable, which i done belive

[S2central.net]

IIRC the B3 and B4 rear diffs are the same except that the B4 has a longer front section which allows them to be transferable as the rear mounting points are the same. I could be wrong on this though - been a while since I was under a B4Q.

[Sleeper_Avant]

they look identical besides the removable nose drives Paul,

but the B3 mounts in the pictures, the castings have no threads drilled

i can drill and create the threads if it will make the diff more desirable and useable to B3 owners as i got lots of questions from B3 owners asking if the avant diff will fit a Coupe

see in the pics below, the thread castings for the B3 mounts are clearly visable but not finished

[S2central.net]

Yes I see what you mean. I would agree that adding those threads in the B4 diff casing will make it fit the B3 but it's best done with a b3 diff side by side for measurement to be certain.

[Sleeper_Avant]

worst case the holes on the mounting brackets could be slightly enlarged/reamed out if you screw the drilling up

Also are the B3 output flanges 108mm? i know B4 Avant ones are 108mm as ive just sold a pair!

[Biturbo]

worst case the holes on the mounting brackets could be slightly enlarged/reamed out if you screw the drilling up

Also are the B3 output flanges 108mm? i know B4 Avant ones are 108mm as ive just sold a pair!

If you have more this output flanges 108mm,let me now.I need some.Or we can swap to 100mm if need I have pair.

[caterpillar]

intercahangeabel parts

If you have more this output flanges 108mm,let me now.I need some.Or we can swap to 100mm if need I have pair.

they are interchangable... take 30 sec to change...the mostly parts in the rear end are intercangable; some models does have the mounting brackets in the castings, and arent screwed in.. and the rear end bracket... in my vw 32b quantum, i use the housing, without the mounting brackets...
i havent checked out the spline for the 1,8 versons quattros, the do have some smller unit in the open diff, but the ratio( cron , and pinion) are the same as the other audi cars

[speeding-g60]

being in the USA, i dont have as many models as you do to look at.

BUT, what are the gear ratio for the B4? here in USA, the B4 has the long snout rear diff and 3.89 R&P / Final Drive.

whereas the B3 has the 4.11 gear set.

here in USA the B3 only came with 100mm rear flanges. BUT, in EU i know the 4cyl Coupe had 90mm flanges/axles, the standard CQ had 100mm like USA, and the S2 3B/ABY/AAN type had 108mm flanges/axles.

ETKA says that all the internals are identical, the changes were the axle flanges and the breather tube on top of the diff. that is the ONLY DIFFERENCES i read about.

http://www.motorgeek.com/viewtopic.php?t=8293