warmongoose

Before starting I like to mention that I did used the search option, but no luck. Can any one tell me what will be the best way to up grade my rear diff.
This is my daily driver."hope this helps" I have a 1998 z28 A4, it has 63000 on it. I just replaced the diff oil in it and it all looks good for what i saw but its making a humming sound, i do not know if this is a normal sound, but when I put it on revers i hear noice.

Thanks.

warmongoose

Please can any one give me some good advice.
Thanks.

ActionJack

I am not sure why you are getting the noise? Sounds like only in reverse.

I would try posting this in the 'Automatic Transmission' area. I can tell you that it is not a normal sound when in reverse.

warmongoose

Yes I also came to that conclution But what about the humming sound. when I let go of the gas. I hear a humming sound coming from the rear of the car I think is from the diff, but I just had it service and the fluids were replaced in cludind the aditive for the slip diff.

jaberwaki

not all "humming" from the rear is a problem...
most people that do gear swaps, rear end swaps ect ect ect.. have there rears "sing" to them all the time...
so dont let the hum alone worry you... if it is coupled by other signs like only lighting up one tire when you do a burnout, then i would worry...
also if you start to hear what sounds like broken glass being churned then it is toast....


but looking at your post the sound started after swapping fluid... also not uncommon...
if they used gm additive, then its almost normal... lol... i dont know why but i have always gotten gear noise using gm additive, but running ford additive, no noise... my 4.11 gear 9" rear is more quiet then most stock 10 bolts...

warmongoose

Thanks for the info. About the humming, and yes I was looking over my invoice and they used GM additive on the diff, I think as soon as i get back to Fort Hood TX I will up grade to maybe a 4.11 and a new converter for my tranny, what is your recomendation on this combo.

Pegleg

I had 3.73's in my rear for a while and sometimes you could hear a little humming of whistleing but its no big deal. I have a stock LS1 rear in my Lt1 now but I am going with 4.10's soon

jaberwaki

4.11's ? you have a 9" rear?
if not then it will be 4.10's...
either way 4.10-11 gears are mannly for M6 guys... if you dont care about driving around at 3000 rpms then fine... but if not then i would stick to 3.73 gear out the back.
as for the verter, stalls 3200-3500 for street use...3500-3800 for street/strip.
and 3800-4400 race car... (subject to opinion, but these are fair i think)

most people on here use vigilanty or yank....

2MuchRiceMakesMeSick

Your right jab 4.10s are way too high for an A4. Youll be banging the rev limiter in the 1/4th. Get the 3.73s

OneMean6spd

im looking to get a programmer for ls1 what do i get hypertech or preadator

jaberwaki

not flaming ya here, but start your own post....and the answer is neither....
either get a real tune, or buy tuning software(hp tuners, ls1edit, flashscan, ect ect ect...)