I talked to a gear shop that has done hundreds of rear ends. I have a 2wd hemi shortbed 2010. 20" wheels. Im wanting to switch from my 3.21 to a 3.92.


The mechanic acted like 3.92 is way too much gear and 4.10 is way way too much. He said that 3.92 would kill my gas mileage and they usually only put those on 4x4s. He thinks i should go to a 3.7.

Wondering if you guys think 3.92 is too much. He said either way total cost would be $1000.

 

well I myself would opt for 3.92's at least with the stock ratio it would be harder for dodge to claim that your rear end caused the tranny to go out. not saying they would not try but harder to claim if you went with a ratio that was offered from the factory, now if your not worried about that, and you can afford the extra gas and want the extra ummp then go 4.10's

 

well, i have heard guys say go with 4.10s, but he acted like thats crazy. I guess i will tell him 3.92

 

I would do the 4.10 since you have 20" rims You are paying a grand for it, make it worth it. I wanted 4.10's but it was only on 4x2. And the mechanic is giving you bum advise with that rim size and tires. This is the biggest performance gain you will feel. If you are worried about gas mileage then just keep the 3.21.

 

go with the 3.92s

 

Well, 3.21 arent that good. They use too high rpm to get goin. I do 36 miles round trip to work about half city half highway. Im only gettin 15mpg. I can get 20 highway if i drive to kansas city and not stop. Of course it doesnt help in Kansas that there is always a 30mph wind !

So, i dont think the 3.92 is goin to hurt my mileage much. But i dont want to get 4.10s if its going to have a jerky too much torque feel and 11 mpg.

Just trying to get some good advice. Thanks

 

It's obvious that this shop that has done hundreds of rear ends is completely unaware that your transmission has in essence 2 overdrive gears...

4.10s is a perfect gearing for optimum performance and fuel economy with 20" wheels and 32-33" tires unless you basically live on the interstate...

 

Interesting. I know the 4x2 rt comes with 4.10. So it must not be too bad. I have a hemi slt. I think i will just roll the dice and go with the 4.10.

 

I have 392s and highly recommend them. I have used about every gear ratio avail growing up hot rodding. The 392 is perfect for my truck. 2000rpm at 70 on freeway and I have 17" tires. If you have taller tires, even 411 would work. I'd stick with 392 mopar for warranty. Also, I get 19-20 mpg on road with 392s.

 

I'm thinking about going 4.56.... but I also have a lift kit pushing 37's. My point, if you are going to change it, get the most bang for the buck. I would go with the 4.10's if I were you. Your MPG loss wont be much if any compared to the 3.92's, so get that little bit of extra oomph!