When I am driving my truck - see sig for details - I always seem to be lugging it due to the tall tires 37's and 3.55 gears. When the trans locks up at 55mph the tach is showing like 1300 or so RPMs. I am just wondering what gears everyone would recommend for my truck. This is a DD and I would like to tow lighter loads 8k and less from time to time. I am also going to sled pull and drag it from time to time.

Thanks

Paul

PS where would a good place be to get gears?

 

either 4.88 for more power or 4.56 for more power and still get a little better fuel milage. a 4.56 will put the truck back to almost the same rpm @ 65 mph as it had stock with the 3.55 gears a 4.88 will be about the same as stock with a 4.10.

 

I agree go with the 4.56 you will be very happy and it will take some stress off of your trans

 

The link below goes to a nice spreadsheet that Ken Lenger put together. You can put in your info/choices and see what rpms you will be running. Just scroll to the right for your specific trans (there are two sections for each trans makes it great for comparing).

http://www.klenger.net/dodge/general...calculator.xls

 

I run 4.10 with 35's and wish I had a little taller gear! I wouldnt go any lower than 4.10, because my truck shifts into OD at 45mph and at 70mph I am turning almost 2100RPM's. I would just get a good tranny with a good TQ Convertor and you should have no problems... if you're lugging it turn of the Tow/Haul.

So I say 4.10's... wanna trade me?

 

The tow/haul? I am unfamiliar with that. Also, if I go with 4.56 will i need to get new carriers front and back? I also drag race this truck from time to time, so what will my top speed with the 4.56.


As far as the spreadsheet what will the height of the tire be in mm- i am coming up with 939.8 mm = 25.4mm/inch * 37" tires??

 

in the sheet if you go down a few cells you will see a label that says "DIA" that is for diameter. The 37" is your total diameter. You can plug that value in there and it will overide the mm in the calculation. That cell is a calculation and once you put 37 in there and you want to change it you will need to close the sheet and open it up again. Though you shouldnt need to change it since that is the tire you have. Then all need to do is change the gear ratio which is at the top of that same column.

Or you can use I think 355 would be it in mm. At least for 37/75/16 tire.

 

My brother runs 4.30's with 37" tires and able to run 113 mph in the 1/4 with some rpm left over. It is right around the same gearing as 265/75/16's with the 3.5 gears.

 

Would never go more than a 4.10! I run a 3.55 and its perfect for 33s or 35s would step up to a 4.10 with a 37... 4.88s??? you will be screamin!!

 

IMO A truck that is using a larger than stock turbo should run a slightly higher numerical gear than one using a stocker, it will help you get rolling easier and help the turbo spool up better. Especially if you want to tow! In a perfect world I would want 4.10's on my rig with 35's and 4.56 with 37's or 38's...

 

2100 rpm at 70mph sounds pretty much perfect to me! Why would you want taller?

According to Cummins, a Dodge with this gearing is already too tall

 

Id rather be at 1800rpms when cruising at 70mph! Thats just "ideal" in my little world! LOL