67HotRod

Sound like I have the same problem as lowtyd, what's that tsb#?

pittom

TxDiesel007 is correct in saying the big tires are bringing you down. if you had 4.10 with 315's it would be better. i have 4.10 with 36'' tires to bring my rpm down on hwy for better mpg,it like having 3.73 insted of 4.10. the best part is, if i have to tow something very very heavy i put on stock tires and back to 4.10 with out changing gears.

CSAGrey1

Dang,
ANd I really wanted to go with 315's as soon as my toyo's are shot.
But everyone seems to think this is a bad Idea. I have a Dr. performance stage 2 comming as well as a AFE intake that should help a little but I dont want to wind up right where I started. I dont really tow alot except the car hauler every now and then (usually no more than 9,000lbs) HOw much umph would you have to have to comoensate fro the loss of the bigger tires and still be doing better than stock?

ddestruel

I run 315's with 3.54s on both my 02 HO and on my 98 12v and have 0 issues maintaining speed all the way up Donner pass with up to 10k lbs. I like it because i can tow in direct most of the time saving my OD alot of wear and tear. 55-65 MPH is perfect in Direct, my fuel consumption is still reasonable in the 12-14mpg range and at 65-70 mph i can swing OD and be right back in the bottom of my torque range. 600 MW is right on. I have run 315's for alot of years towing up to 30k lbs all over montana, idaho ect and i found the little difference between my 285s and my 315s was not offset by the convenience of being able to pull whitebird pass maintaing the speed limit at 60-65 mph+ in direct with a loaded 15k lbs trailer behind me and still had rpms and mph to run in direct if i had to pass someone in a pinch (that was with a bombed 12v truck and 6spd but the point is i was able to use direct and i wasnt wound out rpm wise, 285s wound me out between 60-65mph and left me nothing more)


In stock form with stock tires the cummins should come with 3.23 gears or something like that, because on the top it has always irritated me that in OD you are stuck in OD where as if they gave us the slightly better gearing so you can down shift when passing at highway speeds i would like it alot better. Alot of the guys i used to run with when i pulled trailers ran 3.54s on 235's with aux OD's Gave them the ability to tow in 5th gear direct and with the aux OD on it was ideal for 70-75 mph towing across the western states and then for passes or to pass a car on a two lane road ect drop out of OD and you could wind her up and get 70-75 mph in direct.

erics76

It still amazes me to see people that say how their performance or towing has gone down and they don't know why, then you find out they put 35 inch tall tires on their truck, and the tallest factory tire available from dodge is a 265/75R16 which is only 31.5 inches tall. Most trucks came with 30.5 inch tall tires that didn't have the wheel and tire option. A five inch taller tire with no gear change will greatly effect your truck. To figure out what gear ratio you need with larger tires, use this formula:

new gear ratio= new tire size x old gear ratio / old tire size.

so if you wanted to put 315/75R16's (35in. tall) on and you had stock 245/75R16's (30in. tall) with a stock gear ratio of 3.55, it'd look like this:

35x3.55 / 30.5 = 4.07 so you'd need a 4.10 gear ratio just to get back to your stock gear and tire ratio.

LOWTYD

Everyone, Thanks for the replies. I dont want you guys to think im a idiot,thinking that the 315's,(same size as 35's) arent going to affect the way my truck tow's. This is my third CTD Dodge. I put 315's on all of them as soon as they rolled off the lot , so im use to the shifting thing w/ the 47re, just want to know the best rout to go.Ive got everything covered except some type of fueling box.Leaning towars the Banks Big Hoss, but also looking at Hypertech because of the ability to ajust for tire size, and read codes. Im not taking the tires off, they are on there for a reason, not just for looks. I would like to get some advice on which box to go with, i dont want to be a guinie pig.I guess my 03 H.O. six speed spoiled me.

erics76

The Edge Comp would do more for you than the hypertech unit. I've got the Edge EZ on my 2002, and i like it but i wish i'd got the Comp instead. More power never hurts. I don't know much about banks products, but they seem to be priced a good bit higher than other boxes. Of course with any of the boxes, you'll probably need to upgrade the auto trans soon after.

RAM2940

I ordered a set of rv275 injectors and was thinking about putting on a mild fueling box(quadzilla or edge), but was concerned about doing damage to the auto tranny. I just hate to spend $2500(transmission upgrades/injectors/fueling box) to get the truck the way it should have performed from the factory. I drive alot on route 40 virginia.

AAmeeting

I have stock tires and a 4.10. I can pull a 5000lb boat like it is not even there. good ole .02

ChevyEater

I have 315's with 3.55 and it pulls just fine. even before when all i had was a comp box, i pulled about 10k lbs. on level 2x2 and it did just fine. I dont know that its ur tires and rear ratio, but it could be because of the auto tranny shifting at certain speeds.

pittom

i just towed a bobcat worked good with 4.10 and 36"tires until i had to go up this hill (clif is more like it) with out a start. Started to over heat so stoped 10 min. I put it in 4 low because i did not want to burn up my trans.

except for that hill(don'tgo up to many of them with out a start) it pulled just fine.