3:73,s or 4:10,s ?

[ERoss]

I am going to buy a 2005 ram 2500 ctd with the 48re auto.

I don't tow very often but I plan on running 33" tires and

I don't know what gearing to get? (3. 73 or 4. 10)

Can anyone tell me what rpm I would be turning at 75 mph

with each gear ratio?

Thanks for the info.

 

[BHolm]

33's are not much bigger than stock. 285/70-17s are pretty much 33's and I am running that size BFG AT on both of my quad cab srw trucks. All three of my trucks have the 3. 73 gears with automatics and I have never felt the need for a deeper set of gears even at 28k lbs gross in the mountains.



I can only guess at the rpms until I make it a point to look when I drive it next but 75 with the bigger tires is right about 2000 rpms. This with the speedo corrected accurately for the larger tires. I think the 4. 10s are just going to hurt milage.

 

[Hokey]

rpm/gear ratio

My estimate puts you at around 2200 rpm at 75 w/4. 10's.

If it were me I would stay at 3. 73's unless you pull alot of weight real often or are planning on larger tires. 33's are a good size not that much larger than stock 265 70 17's. my . 02 cents.

 

[Matt400]

Sounds like you need 3. 73's

70 mph is my max before she starts wasting fuel and is 2000 rpm. I have 3. 73's, 33" tires and 48re. 4. 10's are nice for 35" tires.

 

[Blakers]

I run 35s with 3. 73 gears and my truck and I are happy.



Blake

 

[Bertram65]

My truck is gutless below 2000rpm towing only 9K pounds, once below 2000rpm on a hill it just gets pulled down till I shift it into 3rd. I have not noticed any difference in mileage if I run a tank of fuel at 1900rpm or 2500rpm, at least on my truck the mileage does not change at all over 2000rpm. It is also better for the life of the 48re to have the engine turning at a higher rpm, if towing or not.

 

[Tim]

4. 10s have no place in an Inline 6 powered Diesel truck in my opinion, unless it has 40" tires or larger.

 

[Bertram65]

4. 10s have no place in an Inline 6 powered Diesel truck in my opinion, unless it has 40" tires or larger.

Try towing below 2000rpm in a hilly area, might change your mind.

 

[DPKetchum]

If towing anything serious 4. 10s is the ONLY gear to have. 10,000 lbs at 68/70 mph with cruise on over hill and dale. Neighbor pulls less then I do with 3. 73s and on hills is always complaning about having to keep throttle mashed to maintain and if he slows its hard to regain speed until the next dale. Mine just hums along. He does get better mileage by 2 mpg as a rule. Can't have everthing.

 

[Blakers]

Try towing below 2000rpm in a hilly area, might change your mind.

My truck will pull hard down to 1400 rpm. Empty it will handle 1200 rpm with no problem.

 

[Cattletrkr]

I tow 25k+ on a regular basis (almost daily) and I hate my 4. 10 rear end. I switched over to Rickson 19. 5's and in doing so changed my ratio (kinda, sorta, not really, but in effect) to 3. 86, and it handles things just fine. Yeah, I know I've got a 6spd not a 4spd auto, but for normal driving, there's no reason to have 4. 10's. If you're towing a lot, and not at freeway speeds, 4. 10's with an auto woud be nice, but not necessary. My 5th gear is the the same as 3rd in an auto (1:1) and I can pull ANYTHING ALL DAY LONG. IMHO 3. 73 is the perfect ratio for combe driving. Unless you're looking for a short distance sprinter (1/8th mile) don't bother with the 4. 10.

 

[crobertson1]

Towing in the Rocky Mtns, I insisted on 4. 10s. It just lets things work a little less hard. I'm all about overkill though .

 

[Bertram65]

My truck will pull hard down to 1400 rpm. Empty it will handle 1200 rpm with no problem.

What are you towing at 1400rpm?

 

[DPKetchum]

I've pulled down to 1600 or less towing 10k. From 1600 up it pulls and acells ok.

 

[DSutton]

I also pullo 10K regularly, and go down to 14-1500 RPM and get good pulling power. As you all should already know peak torque for these trucks is 1400 RPM. I am amazed at how much harder they pull at 1500 RPM, than 2200. What I mean is that the truck on the same hill will more quickly deccelerate from 2200 Rpm's and hang a lot longer at 1500 rpm. But as previously stated, I also am running a 6 Speed manual. The autos will not hold up at that RPM. (I know personally, I traded off the auto for that reason).



Part of this debate is driving style also. I pull 10K and am happy crossing the passes here in oregon at 55-65. In 5th gear I can slowly accelerate on most grades. I do not expect it to respond like its a car. Some do!!

 

[b.ferrara]

sometimes I really get a chuckle reading some of these columns. Bertram 65

made an excellent point about wanting to keep the rpm's up. If your cruising @1700 and need the power ther is no way you will run with a guy who is cruising next to you @ over 2000. I would have to say a 6spd w/4:10's is the way to go if your worried about rpms put a gear vendor in and split 5th and 6th. If you want a truck, drive a truck, if you want to worry about rpms or 1mpg buy a volkswagon they get 55mpg. I made the mistake of getting 3:54 in my 2nd gen and 3:55 in my wife's van, their garbage, the 3:73 might be ok, but I will never own a truck again without 4:10's. Good luck

 

[Blakers]

What are you towing at 1400rpm?

It doesn't matter. That is where the torque is the best whether with a load or empty. And this is not with the throttle to the floor all the time.

 

[DPKetchum]

Towing anything more then the lawn mower its 4. 10s. I've bought trucks with 3. 54s and ended up installing 4. 10s

 

[Bertram65]

It doesn't matter. That is where the torque is the best whether with a load or empty. And this is not with the throttle to the floor all the time.

Guess I will never find out, my automatic will never allow the engine to lug at that rpm.

 

[Kirwin]

Best ratio for towing

I think this is largely a personal thing. One question you need to address is what speed do you feel comfortable towing at? If you want to tow at 60 MPH I would get the 4. 10s. In my opinion the truck will pull better for you at that speed with the 4. 10s. If you want to pull at 70 or more you will like the 3. 73s better and the truck will perform fine. My 03 Ram (with the 6 speed) is not turning enough RPMS at 60 MPH for me to feel comfortable with it towing on cruise. I try to maintain engine RPM > 1600 at all times towing. Even overpass hills can result in short full throttle runs and the associated speed overshoots. The engine "feels" like it would like to be running faster. If I bump speed up closer to 70 MPH, every thing "feels" much smoother and while on cruise the truck rarely gets to full throttle on those small hills. The engine is much happier at the higher RPM and with the new HPCR engine noise is a non issue unlike the 12 valve 2nd gen trucks that got very loud > about 2300 RPM. I recently installed the TST box and have not towed with it yet so I can't say how this will affect engine RPM/power while towing. I frequently tow on I-95 and I don't feel comfortable towing 20K GCVW at 70 MPH with the traffic congestion. These things may help you decide. I think that if I were to get another truck with the HPCR engine (read this as quiet) I'd get the 4. 10s and not worry about the loss of 1 MPG with the truck empty. I don't think it will make much difference in MPG while towing. The automatic transmission is most limiting and will probably last longer with the 4. 10 ratio for people who tow heavy or often. All of the above IMHO. Ken Irwin