Great minds think alike Jim.
I just went back and looked up the post "DOUBLELOADER" made last Jan. about using a 3.70 differential.
I still think it's going to take a steeper gear than a 3.27 equipped SRT6 to break into the 10's on nothing but motor.
https://www.crossfireforum.org/forum...3-7-rules.html

 

I have read that some of the '04 had a problem with gear whine. Do the diff's with two piece axles from the '04's bolt right up to the solid axles from '05's and later?

 

You're welcome.

I'm running Mickey Thompson ET Streets in 265/40/18's, and don't plan on changing them out.

Maybe

Good info

I wasn't aware (or forgot) the early XF's had the flanges. I thought that was only the early SLK's. They don't interchange, but I'd guess the ring and pinion would be the same.

 

Awesome Anthony!! Awaiting driveability and track results.


That is interesting. I have been pretty rough on everything the last month, but don't have a whine or anything. It may be about time for a PM to Anthony lol.

 

I think the car likes the 3.27. This was done today on street tires with no nitrous. I'm very surprised the lower gearing didn't cause a lack of traction. It actually feels like the car is hooking better now than with the 3.07's, and I know that makes no sense. I can floor it a little sooner now than I could before (it seems). My first 0-60 today was an easy 4.2 with me slowing rolling into the throttle. Next I got into it a little sooner and pulled a 4.1. A little more got me the 3.9. Strange but true.

IMG_20131017_164555_564_zps5360c6fe.jpg

 

Woh! With the 3.07 it was 4.3? or there abouts?

 

I did a 4.21 the day I broke the Ring/Pinion (2 weeks ago).

 

Roughly the same conditions? That's pretty awesome.

 

It's around 10 degrees cooler today, but the humidity is around 70%. My point for making the post was to show it didn't hinder my 0-60 time. This was what really put me off about a gear swap. I've always had to really roll into the throttle due to tire spin (excessive power), but with the 3.27's I'm able to be more aggressive on the launch and it doesn't spin wildly. Even if the DA was lower, I've never run that fast on street tires in the past due to tire spin.

 

Thats promising.....very cool.

 

Are you logging your A/F ratios? I remember Steve having all sorts of issues with a lean spot on upshift with the Eurocharged TCU.

 

That was a different vendor's TCU tune and thank you for the head's up. Keep in mind, I warned Steve NOT to install the TCU tune back then (even though it was free) due to what I felt was a lack of research and R&D. Moreover, I'd just watched Jeep and LX owners (with MB TCU's) go through the same thing a year or two earlier.

 

Great job getting a solid base line then valid improvements with your results.

So I need to find a diff now! Needed the wave trac anyways....

Thanks Anthony!

 

Anthony, in the old days, I ran a 3.73 rear end in my big block Camaro... It just gets you up quicker in the rpms, and torque usually remains the same...so, if a stick, you will grab gears sooner, but won't be so noticeable in an auto.. I drove a Nova once thru the traps with 4.56 rears and it was a screamer, but launched the same as the Camaro...just grabbed 4 gears as quick as I could...and it topped out about 115-120 mph... There were 4.88 and 5.56 gearing around back then as well...cars would top out in the 1/4...if not before....

 

If the ring and pinions only last a year (at least for me), why even buy the Wavetrac? If I were you, I'd just buy a 3.27 for $250 shipped and have a local shop swap out the Yoke from the 3.07. Install the carrier yourself (with a friend) and install the modified (Rudy) TCU and call it a day. If you're making big power, you're going to kill the thing in a year anyway. Just food for thought. Think of the carrier as having a 1-year life span and budget it in.


I bet that was a hell of a lot of fun. I imagine launching with 4.56 gears and hooking was like my old 800HP Jeep. It ran out of steam early, but would snap your neck and get to the finish line quicker. Holy hold on Batman!

 

Deleted - duplicate of the above.

 

yep!, you want it done right call Rudy. that goes for engine swap and ecu,& tcm tuning .. jim

 

Your 3.27 ratio sounds interesting for a SRT-6. I could ditch the 30 series sidewall tires then move up to the taller 35 series. Filling out the fenderwells and remaining near the stock 3.07 ratio (I'm guessing). Squirrel Crusher

 

I did some additional head scratching and searching and now realize what I've always thought about lower gear ratios was backwards. I've always assumed that lowering the gearing would make the tires spin easier on launch, and this isn't the case. It's actually the opposite.

It takes more engine RPM now to get the tires to turn as fast as before (duh, I know). Now that the tires spin slower on launch, I get a more a more controlled tire spin, and the car still manages a decent 0-60 even spinning. Before the swap, the tires would sometimes spin violently if I got too aggressive on the launch, which would kill the 0-60.

Anyway, I feel really dumb for having such a misunderstanding of gearing, but I'll get over it... one launch at a time.

 

Now you are getting it. Today, we have 5 speeds, or even more. What they have done is use gearing in the transmission to move cars a little quicker out of the hole, but get better fuel mileage on the top gear. Kind of an over drive. MB and others, now Dodge, are offering 7 and 8 speed trannys. This is for better fuel mileage as well... In theory, you really only need 2 gears for the 1/4 mile, 1 to get you out of the hole quick and the other to finish. A 3 speed is perfect for most cars...Bottom line, I will love changing gears in ole blue.....I take what ever I can get that will hold up...Rudy will get a call tomorrow. LOL....
Getting old my point being that is why rear end gearing is in 2.92 to 3.27 area. Because there are more transmission gears. In the old days you had a choice of 3 speed or 4 speed manual. Auto was 2 or 3... So rear ends were geared higher to get the car moving.