View Full Version : Rear Gears

03-01-2005, 06:09 AM
I have an '03 Cobra with 5,000 miles on it and I am considering a new rear gear ratio. I'm looking for some ideas/expertise.

Should I upgrade to 3:73 or 4:11?

Is this hard to do?

Should I consider another type of limited slip unit (Torsen, etc.)?

Is that factory backlash necessary, can it be adjusted out to not clunk so much?

Thanks in advance for any help.

03-01-2005, 11:23 PM

My first question to you is why do you want to change gears? Are you going to the dragstrip a lot? The stock 355's are pretty good and you probably won't feel too much difference with 373's. I heard the 410's make you lose first gear once you spool up.

Changing gears out is best left to the professionals. They usually have a mic and measure clearances (tolerances) to make sure you don't have that clunk or back lash. Expect to pay for 10 hours of labor at the Ford place if you supply the gears (Which I recommend). Bottom line...about a grand would be a good ball park figure. (I just had gears installed on my NA 94 Cobra).

Yes the clunk can be minimized some with new parts installed.

Hope that helps?

03-16-2005, 11:24 AM
so the clunk is normal?

RF Cobra
03-16-2005, 06:39 PM
so the clunk is normal?Yes it's normal.

03-16-2005, 06:59 PM
why are the tolerances on the IRS's not as tight as those on the solid axles? i never experienced this until just recently when i installed my new IRS.

04-02-2005, 07:02 PM
Here are some pics of my 3.73 install.

BTW they turned out great,whisper quiet:headbang:

First pic is center section fresh out of the Cobra!It only has about 5,000 miles but was starting to show signs of a leak.
This pic was just after I removed the cover.

ewwww,,,Not Good for only 5,000 miles.

I didn't expect everything to be so filthy with so few miles?

New 3.73's,Bearings and shims installed!

Set the new backlash at .009 Old setting was loose at .015 :nope:

Checking contact pattern,,,,everything looks good.

Bottom tapping all the cover bolt holes.

This is what came out of most of the holes,,,maybe why some were breaking cover bolts at only 24ftlb.

And to top it all off :hail: The Billetflow Brace is awesome!!

Hope you enjoy the pics,,,install was very strait forward!

04-02-2005, 07:22 PM
Good pics...I need to get my brace on soon. I'm on my second rear end and this one is starting to howl slightly at 75 mph :rolleyes: I don't think they spend too much time getting these pumpkins set up properly at the plant. I'm sure I'll be doing gears sooner of later.


04-04-2005, 09:59 AM
I got mine in the mail last week...definitely putting it on considering I should be in the 650+rwhp range when I get done...now just hoping the halfshafts will hold up for a little while :D

04-04-2005, 09:52 PM
4.10's are overkill in the '03-'04's. You'll redline too quickly to get full boost. We put 3.73's in ours and the difference isn't a lot but it's noticeable. Exhaust note sounds better, too!

04-09-2005, 01:44 AM
I also told 4:10s would be too much, but only for rpm and getting the most boost from you car. I went with 3:73 Ford Racing gears and love them. I paid approx. 4 bones for the install which took a day and a half. I have noticed a little diiference in the acceleration, but rpm wise is only changed by about 200 rpm.