Need Help with 3.92 Gears and LSD
Thread Starter
|
Professional
Joined: Aug 2007
Posts: 209
Likes: 0
From: Upstate, NY
Need Help with 3.92 Gears and LSD
So I went to Pure PErformance in Troy, NY today. I have decided to lift my truck and do Coil overs in the front and progressive rate springs in the back. I also will need to increase the tire size from factory to a 35x12.50 18. This also requires the need to change from my factory 3.55's to 3.92's so of course I want to do front, rear and lsd. anyone know where I can order the parts from? is there anything special needed? (carrier??) any help would be greatly appreciated.
Rookie
Joined: Mar 2009
Posts: 69
Likes: 0
From: Upstate NY
Its good to see that you understand gearing and mechanics, I did a gear swap on my '05 which uses the same running gear, so I can help you out. First of all, if you are going with 35s, put some serious thought into running 4.10s or even 4.56s. Right now I'm running 34's (275-65-20) and IMO the 4.56s are perfect. Granted the VVT hemi has much better low end drivability, but you still have the same tranny and same ratios as me and you are going 1" bigger on tires. I do have a spreadsheet which makes tables and graphs of speed vs. rpm for various tire size and gear ratios, if you want, I can email it to you.
As for parts, I worked with justdifferentials.com if I remember correctly; there are others out there too, check them out online. For the rear, I went with Yukon ring and pinion, but supposedly Yukon doesn't make their own front R&P and it is made by Motive, so I went with the Motive.
Whichever manufacturer you go with, for each axle, you will need a ring & pinion set (~$250+) and a full installation kit (~$150+ I believe). Obviously the biggest thing is labor, the rear is easier, but is still labor intensive. The reason that you need the full installation kit is that the bearings (pinion in particular) should NOT be reused (been there done that and had a failure, they have to be pressed on and off)! My friend who did mine (20+ yr Chrysler tech) used an old bearing and honed the inside to allow it slip on and off easily, as it is some trial and error in the shimming to set the backlash and contact pattern between the R&P.
This is certainly not a backyard project, as the contact pattern is critical to avoid noise and wear. Figure $1000 per axle to get in the ball park. Feel free to ask anymore questions.
As for parts, I worked with justdifferentials.com if I remember correctly; there are others out there too, check them out online. For the rear, I went with Yukon ring and pinion, but supposedly Yukon doesn't make their own front R&P and it is made by Motive, so I went with the Motive.
Whichever manufacturer you go with, for each axle, you will need a ring & pinion set (~$250+) and a full installation kit (~$150+ I believe). Obviously the biggest thing is labor, the rear is easier, but is still labor intensive. The reason that you need the full installation kit is that the bearings (pinion in particular) should NOT be reused (been there done that and had a failure, they have to be pressed on and off)! My friend who did mine (20+ yr Chrysler tech) used an old bearing and honed the inside to allow it slip on and off easily, as it is some trial and error in the shimming to set the backlash and contact pattern between the R&P.
This is certainly not a backyard project, as the contact pattern is critical to avoid noise and wear. Figure $1000 per axle to get in the ball park. Feel free to ask anymore questions.
All Star
Joined: Jun 2009
Posts: 975
Likes: 0
From: San Antonio, TX
The 3.55s should be able to turn them, but you'll have no pickup at all. Gun it and you'll feel like you've got the V6 under the hood rather than the HEMI.
