I am getting ready to buy an 09 Ram 1500 and I'm coming from an 04 Ford F-250 with the 6.0 Powerstroke Diesel. I was looking at the options and the one truck on the dealer lot that I really like has the 3.55 gear which is not an issue. When I started to look into the 3.55 gear, it appears that this particular rear end does not have the anti spin rear diff, am I right? It looks like I would have to go to the 3.92 to get the locking rear diff. So does this mean that the 3.55 is just an open rear end and will not have any locking capabilities? I'm torn between the 3.55 and 3.92 and the only problem with the 3.92 is decrease in fuel economy and I would have to order it. If anyone can shed some light on this, that would be great. Thanks

 

the 3.55 is a open end rearand the anti spin is not an option,the 3.92 has the anti spin differential the difference in mileage especially with the mds should be minimal 1-2 mpg at most

 

Correct. 3.55 is open. 3.92 is locking. Mileage difference is about 1 mpg.

 

3.55 open, but with TC, not that big of a problem. If you are getting 20s, get the 3.92. The engine will turn just less than 200 more rpm and the mpg is the same really. On the highway, you might see .2-.3 more miles per gallon. In town or pulling a heavy trailer, you will get better mileage with the 3.92. I have the 3.55 because that is std on the sport model. I would much rather have the 3.92, just could not find one at the time and the demo I bought had the 3.55. I will put it to you this way. If you get the 3.55, you may have wished for the 3.92. If you get the 3.92, you will never wish that you had the 3.55. If you are getting the hemi with 20s, the hemi is smoother at 70 mph turning the slightly higher rpm of the 3.92.

 

I put 4.10's on my 07 from 3.92 (thought i had 3.55 like it said on the sticker) anyways, It picked up in town by 1.5 - 2 mpg and i lost .5 on the highway.

hope that helps..Putting 4.10's in my 09 next month.

 

for what? just curious.

 

I like the pick up with the 4.10's plus it helps around town MPG....i don't do alot of highway driving.

 

0436,
I don't understand all of these guys that are concerned about getting too low of gearing. Heck, if you are getting 20s, you can go down to 4.10 and not have to worry about it. I remember back in 02 and 03 if you got the factory 20s, you had to get the 4.10. It was part of the package.

You just supported the point that I have tried several times to explain on other threads. Going to a lower gear will increase you mileage in town and when towing and your highway mileage will hardly drop any at all.

I have the 3.55, but would like 3.92 or 4.10 LSD. How much did it cost and what brand of ring/pinion are you going to install?

 

I thought in 03 3.92 gears is what came standard if you had the 20's?

 

Moesperformance.com...he has everything and it's the cheapest I've seen. You can get gears, depending on the brand from $160.00 to $300.00.