So I've decided to have some gears and underdrive pullies installed. I wanted to go with 4.10s but from what I've read I should also go with the extended tailshaft housing and aluminum drive shaft. Then I considered 3.73s. What's the consensus on 3.73s? Do I need the aluminum drive shaft and extended tailshaft housing for these also? I never drive over 80mph, except at the drag strip and it's barely over 80 (81.8mph, see a previous post from a couple of days ago, I'm a mile above sea level). Anyways can I get away with my stock driveshaft ( I have an 01 LX Sport) with the 3.73s? What about with 3.90s?

In addition to gears I plan on Steeda underdrive pulleys, a traction-lock rear end and an SCT XCAL2.

Thanks for your help. I did a search and it seemed there were differing opinions as to what point a aluminum or metal matrix drive shaft and extended tailshaft housing are needed. Also, does anyone have a link to where I could purchase the new driveshaft and tailshaft housing if need be?

I( don't think anyone has done 3.90's yet. thats what I'm doing next though.

I would get the aluminium shaft and ext. housing with the 3.73's though.

Seems like everyone has gear fever lately

I have 3.73's and I really like them. Like Quickvic30 said...do the driveshaft and tailshaft housing. Keep in mind, the XCal 2 will not correct the speedo change. '03 and up you can. You still need the XCal to reprogram the ECM for the gears so the shift points will be correct. But in order to correct the speedo being off, you need to replace the speedo gear in the tailshaft. It should be either the black or white 23 tooth. I have the white 23 tooth in mine.

I know a member on the MM.net site who has done the 3.90 gears. He likes them.

I really don't want to have to get an aluminum driveshaft and extended tailshaft housing. If I go with 3.55s and a traction-lock would I still need the aluminum driveshaft and extended tailshaft housing? Would it even be worth only jumping from 3.27s to 3.55s? I'm fairly certain the Vic (01 Sport) has 3.27s to start with. Thanks.

drock went from 3.27 to 3.55 recently. he noticed a gain. you ought to ask him his impressions.

some 01's received 3.55, check your door tag.

http://moldyrabbit.com/liquid/data.html

Pretty positive you have a 3.27 open out back. You don't HAVE to get the shaft, but it is recommended with gears 3.55 and lower. I was told a while back that even if I didn't travel at 80 mph or above, the resonance would still be there. The effects will probably take a little longer to show themselves than if you drove at 90 all the time, but the effects will still be there.

Just like you, I didn't want to get the driveshaft and mess around will all that. I'm glad I did though.

the tailshaft and aluminum drive shaft should be installed for anything 3:55 or lower. They can be aquired from your local salvage yard pretty cheap and if you are lucky maybe you can find a MMC driveshaft..

If your 01 Sport is an early build it may have 3.55s, other wise 3.27s (open for both)


You can use the stock steel shaft with 3.55s as long as you keep your speeds 'normal' (ie less than 90-100 when cruising)
This is how the 00-01 (early) HPPs left the factory with 3.55 RAR.
You probably will NOT notice any driveline harmonics with this setup below those speeds. This is also how my car is right now, and it cruises comfortably at 75mph with no vibration at all (I also made sure to index the d/s to the companion flange, though)
If you do, you could also have your stock steel shaft rebalanced by a driveline shop to help with any highway vibration (or upgrae to aluminum shaft)

If you go with anything lower than 3.55, or plan on traveling at high speeds, I'd get the aluminum shaft (and long tailshaft) immediately post install. As even at highway speeds these ratios will put the drivline speed very high.

If you go with 4.10s, or the 3.90s, plan on the AMMC shaft (or custom carbon fiber) rather than the more easily found aluminum. The driveline rotational speed will be VERY high with these ratios at fast highway speeds.





On -02s, you need a new speedo gear (exc 98-02 TC) along with a tune for the shift points. If you go with anything above 3.55 RAR in a -02 w/ 8 tooth VSS drive you will need an electronic ratio adapter with a stock speedo gear to correct the speedometer. Your 01 should have an 8 tooth VSS drive, but you can pull yours and look at the gear color to calculate which drive you have for your ratio. The 7 tooth was used on 99-02 CVPI.


Also note, if your tires are taller or shorter than stock it will effect your actual final drive ratio. Taller tires will make the ratio higher (lower numerical RAR), shorter will make it lower (higher numerical)

I went from 2.73 to 3.27 and really liked the difference.

After a while, though, I decided to go from 3.27 to 3.55. The 3.55s are definitely my favorate
Though this seems like it was not a worthwhile improvement, it was. All around the 3.27s felt good, but with 3.55s it just feels right

Now, I installed mine myself both times so switching them out wasn't a big expense. If you are having it done, with install rates going around $400, 3.27->3.55 may not be a worthwhile upgrade to YOU, in which case I'd go with 3.73.
For those that still have 2.73 or 3.08, though, I'd go with 3.55 from the start over 3.27. But that's just MHO.



Some good discussion in this thread:
https://www.crownvic.net/ubbthreads/ubbth...rue#Post1230924

Derek,
I believe the Sport came late in the 2001 model year. I have seen early HPPs with 3.55s, though.

There are just a few 01 Sports out there with a 3.55 RAR, there are even some with digi dash! (01 only)

Yep, my Sport has digi dash.