blac94Z

hey whats going on dudes
i am going to be buying a
yukon dura grip posi
and 3.73 gears
with a yukon bushing/bearing kit
now my question is do i need anything
else to go with this kit to rebuild
my rearend ? And do you guys
think 3.73 will be too harsh for
street/hwy use. i do go to california
pretty frequent will i see a big change in gas milage
(dont care that much but i would like to know)
i get fill a full tank and still have right under a 1/4 of tank left when i get to
California
thanks in aadvance for your help you guys

FirstYrLS1Z

3.73s' are the preferred/ideal ratio for A4. Some A4 users are even going to 4.10s',I ran 4.56s' for 4 years.
Can't speak about MPG with an LT1 engine,but for reference,LS1s'(freeway mpg) with 2.73s get 26 and 3.73s' get 23.

Injuneer

Are you doing this install yourself? Do you have a magnetic dial indicator, a pinion depth checker, inch-lb torque wrench, and are you familiar with using gear indicator paste?

blac94Z

Will keep that in mind FirstYear

And No no no I found a driveline shop to do the labor I am just
Supplying my own parts lol
I just really want to know will 3.73 be alright for street/hwy use and if any one has any insight on the Yukon dura grip posi

Injuneer

You're going to see a huge increase in RPM compared to your 2.73 rear. On the other hand, I believe you are running 20" wheels with 27.7" tires, so that will temper the RPM increase a bit. I think I gave you the "effective" gear ratio running 3.73's with 27.7" tires, compared to running them with stock tire diameters (25.7" or 26.2").

With 3.73 gears, the RPM at any speed in O/D will increase 36.6%.

My calculator shows 2.73 rear with 27.7" tires, 4L60E in O/D @ 70 MPH = 1,614 RPM

With the 3.73, 27.7" tires, it will be 70 MPH = 2,205 RPM

If you eventually put the right size tires on the car, the RPM will go up.

You have to decide if you can live with that. 4.11's and 4.56's are probably great for the track, particularly an 1/8th mile strip. But I wouldn't think they would be all that great on the highway on a daily driver.

FirstYrLS1Z

'I just really want to know will 3.73 be alright for street/hwy use'.

Why would they NOT be alright ?

Injuneer

Appears he is concerned about a drop in fuel mileage.

FirstYrLS1Z

If he's concerned about a drop in fuel mileage,he shouldn't be contemplating a change from 2.73s' to 3.73s' in the first place. BUT since he brought up 3.73s',he also wants the increased performance aspect. Can't have both with a gear change.
As performance goes up,mpg goes down,fact of life.
If he wants better performance(on the street) and still retain his trips to California mpg,a performance lock-up torque convertor would be the way to go. A good 3500-3600 convertor would allow him to jump into a better part of the power curve and still lock-up with those 2.73s' for travelling.

Injuneer

From his question, I think he understands the he will lose fuel mileage.... but maybe what he is looking for would be a number.... e.g. 2 MPG reduction, or something like that.

FirstYrLS1Z

MPG is 'right-foot' dependent.
At freeway speeds,mpg will go down as mph increases. Traveling at 60mph will use less gas than traveling at 70mph because of the increased 'wind resistance' of the higher 10mph. Even though you travel the same distance,it takes more power(more gas) to fight the wind resistance at the higher 10mph.
I've traveled many times(13 times)(most of the times with 3.23s',a few with 4.56s') from Cleveland Ohio to Florida using the same identical route. With the 3.23s',24.5mpg driving with the traffic flow,25.5mpg-5mph below traffic flow,26.5mpg-10mph below traffic flow. Just for reference,the 4.56s' gave 21.5mpg.

blac94Z

well what is the mpg on a 94 z28 ? a4 with 2.73

FirstYrLS1Z

you stated the answer in your original post,all you gotta do is the math.

"i do go to california pretty frequent i get fill a full tank and still have right under a 1/4 of tank left when i get to California"

how many gallons to fill it back up when you get to California and how many miles is you trip to California.
Miles divided by gallons = mpg

blac94Z

true my real question was more or less wondering if the yukon duragrip is a good unit or not

blac94Z

ok so so the kit fell through and I had to rush order a torsen posi off ebay but buyer stated it was for a Trac option 2001 ss so my question is would my rear end be able to accept the posi and gears?

FirstYrLS1Z

need more info
an SS what ?
what series is the torsen ?
what series 3.73s' did you order ?