Rearend Gears

**havnaparty** · 03-30-2010, 01:24 PM

I have a basically stock 99 T/A. Auto 4spd. Bought it new in 99.
Added a magnaflow exhaust and a Ram Air hood with air box,3.73 gears.
My question is this. I really don't have the cash to stick in the motor right now.
Other than bad fuel mileage,what would the cons be to put in some 4.10 gears to get this thing off the line a little quicker. This is an everyday car other than winter months. Will there be much difference or worth it changing the gears?
Thanks.

**Knight** · 03-30-2010, 01:32 PM

Top speed will drop, rpms will be higher when crusing at higher speeds. Tach and speedo will read different too without an adjustment tune. Most people are of the opinion that 3.73s are the best gear for an a4. You might see a slight pickup in your 1/4 mile et - maybe .05 to .1 or so. If you're running a stock stall - IMO you'd be better off putting a better stall and maybe a shift kit + tune instead. Your call though.

**67CamaroRSSS** · 03-30-2010, 02:08 PM

Big stall (3400 or bigger) will put a smile on your face. You'll need supporting mods also like a tranny cooler and tuning. While it's out you might want to take a look at the tranny internals.

If you do gears 3.73 is better than 4.10 for an A4 because we only have 1 overdrive gear.

**oldmanZ28** · 03-30-2010, 08:19 PM

I gained .5 in the 1/4 going from 3.23s' to 4.56s',going from 3.73s' to 4.10s' you might gain .1-.15. Do a stall w/fluid cooler,as you already have the ideal gear(3.73) for an A4.
MPG is right foot dependent,I only lost 3mpg with the 4.56s'.

**tatertot91** · 03-30-2010, 08:21 PM

Originally Posted by 67CamaroRSSS

Big stall (3400 or bigger) will put a smile on your face. You'll need supporting mods also like a tranny cooler and tuning. While it's out you might want to take a look at the tranny internals.

If you do gears 3.73 is better than 4.10 for an A4 because we only have 1 overdrive gear.

+1 agree with all the above

**RyanJM** · 04-03-2010, 03:01 PM

I have an A4 with 3.73's and it's only a weekend toy and I wouldn't go up to a 4.10 unless I was just driving it to the track and meets. With the 3.73's it's at 2500rpm and we do alot of highway driving and even the backroads are 65 to 70mph an usually going faster so my car is always at 3k rpm so I couldn't see 4.10's if you drive it alot.

**SteveC** · 04-04-2010, 04:41 AM

one of the "cons" of 4.10 gears in an A4, would be highway driving. Just say you were doing 70 MPH in O.D., and you need to pass (go around another vehicle), so you give it more gas, and the PCM decides to drop it into 2nd gear, you are now way over the redline, and you can blow the engine.

I have 3.73's and a Y3000 yank stall, and I go from "farfegnugen to fukenmovin".

Get a 3600 stall, and forget the 4.10's

SteveC

**oldmanZ28** · 04-04-2010, 05:31 AM

I have 4.56s' in an A4,the PCM does not/will not drop it into an inappropiate for passing.

**Cutlass** · 04-04-2010, 05:03 PM

Originally Posted by oldmanZ28

I have 4.56s' in an A4,the PCM does not/will not drop it into an inappropiate for passing.

Very true.

**karpetcm** · 04-04-2010, 07:21 PM

Ive never heard a PCM dropping it in a wrong gear just because you've moved up to 4.10's in a A4. This could be something i wasnt aware of but ive never heard of it nor thought it was possible.

**Hi-Po** · 04-05-2010, 05:24 PM

4.10's in the auto would be brutal! In a good way! Top speed obviously and a higher cruising RPM would be affected. Plenty have done it

Just have to play around with gear calculators to see if it would be for you.

It would definitely put some kick in.

I would do a stall way before going to a higher numerical gear though.