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Discussion Starter · #1 ·
I searched but didn't really find what I wanted.

I just purchased a 99 dodge 3/4 ton cummins. I believe it has the 3.54 gears and 245's. I want to move up to a bigger tire--probably a 315. Is this going to effect the pulling much? If I wanted to go to a 37 12.5 r17, would I be ok with those gears, or would I deffinately want to regear?

Cody
 

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MoabZJ said:
I searched but didn't really find what I wanted.

I just purchased a 99 dodge 3/4 ton cummins. I believe it has the 3.54 gears and 245's. I want to move up to a bigger tire--probably a 315. Is this going to effect the pulling much? If I wanted to go to a 37 12.5 r17, would I be ok with those gears, or would I deffinately want to regear?

Cody
I think that the largest tire that you would want to go with is a 285. I ran my '99 with that setup for years and had great results. You didn't say if you had an auto or manual. I had the auto and believe that the 3.54's are better than the 4.10's for towing at highway speed. Problem with the 4.10's is that when you push the button to take it out of o/d, your turning around 2400 rpm at 55 mph., not fun.
If I recall, by going to a 285 tire, your speedo will be off 10%, 50 on the speedo means your doing 55, etc.
 

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Cody,
If you will be hauling the "Cage" on a single trailer only you should be ok with the 3.54s and the 315s. If your new truck is an auto you might like the set up for the Interstate but the mountains would slow you down. Just like when you were using the ZJ for a tow rig watch your temps on the auto. If you have the 5spd add a box and pull away. Best bet would be stop at 285s

I enjoyed seeing the article on you.


Scott
 

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I just sold my 2001 CTD that had 3.54's and 305's. It towed fine on the flats and ko on hills. I did have to push it a bit on the hills. It had an auto tranny.
 

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I have an '03 Quadcab SLT CTD with LT235/80R17E BSW All-Season Tires and 4.10 gears.
I'm at appx. 2000rpm at 60 mph in 5th with the NV4500 5sp manual. I have to
drop into 4th to pull long, steep grades with a 3000lb/ 9 1/2' camper and a 6000lb trailer.
 

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I think the 3.73's in my 03 are just a little too low. But If I decide to go up in size they should be fine.

Lance , is Toyo tires still a sponsor of Pirate4x4.com ? I am filling out something and it asked were I found out about Toyo and I'm putting down Pirate4x4.com :D
 

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flimmy said:
I think the 3.73's in my 03 are just a little too low. But If I decide to go up in size they should be fine.

Lance , is Toyo tires still a sponsor of Pirate4x4.com ? I am filling out something and it asked were I found out about Toyo and I'm putting down Pirate4x4.com :D

Yeah, I'd say they are. Their banner is at the top of this forum. :flipoff2:
 

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SanDiegoCJ said:



Yeah, I'd say they are. Their banner is at the top of this forum. :flipoff2:
I know I've seen it before. But it's not there now :confused: and I haven't seen it all day. Atleast for me.
 

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flimmy said:


I know I've seen it before. But it's not there now :confused: and I haven't seen it all day. Atleast for me.

That's bizaare, cause I see it right now as I'm typing this. :confused:
 

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Lance said:
I can say that my 4.10's are way too low! I'm considering going to 3.73's and 315's. Im leery of going to 3.55's, but I might....
I haven't driven one of the new trucks, but FWIW, I'm happy with my 315s and 3.54s. Motor is a 12 valve, ~360 hp range. However, this is in CO where we don't have a 55 towing limit (not sure if anyone follows that in CA?), for interstate driving/towing, it works great, towing our boat to Wyoming I still wish for another gear.

Pete
 

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Discussion Starter · #14 · (Edited)
Right on. It is an auto tranny BTW.

Well, I found a great deal on some BFG AT KO's in the 305 70 r17 variety (or whatever the metric equivelant to 35x12.5 r17 is). 84/ tire brand new. Couldn't pass that up.

My rig and trailer aren't super heavy--maybe 5500 lbs. If I figured if I can't deal with the gearing I can sell the tires and step down a size.

Another question--how much harder on the tranny are the 35's? I've only had the truck for a couple days and havn't had a chance to go through it at all--but it has 130k miles on it and the tranny fluid looks a little dirty but doesn't smell burnt. I'm going to have a tranny shop flush and fill the tranny and take a look to see what kind of shape it's in (and install the sensor for the tranny temp gauge). Hopefully I can get by for a year or so before I have to do the tranny.

Does anyone know where to get a good deal on a set of Weld rims? I have my eyes on those Mountain Crusher rims but I don't like the 300 dollar price tag/rim.

Thanks again

Cody
 

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Discussion Starter · #16 ·
on metric sizes, isn't the first number the width in mm (i.e. 315) and the second number the sidewall height as a percent of the width (70 meaning 70% of 315 is the height of the sidwall).

so mine are 315 70 17s. However they figure it, they measured 34.5 x12 ish unmounted.
 

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MoabZJ said:
on metric sizes, isn't the first number the width in mm (i.e. 315) and the second number the sidewall height as a percent of the width (70 meaning 70% of 315 is the height of the sidwall).

so mine are 315 70 17s. However they figure it, they measured 34.5 x12 ish unmounted.
Yes you are correct.

285/75PR16 122/119P D
3305lbs.
65psi
19/32nds
7.5-9"
NA
11.3"
NA
33.1"
NA

305/70PR16 118/115P D
2910lbs.
50psi
19/32nds
8-9.5"
NA
12.2"
NA
33"
NA

315/75PR16 D
3195lbs.
50psi
19/32nds
8-10"
NA
12.3"
NA
34.8"
NA

265/70PR17 112/109P C
2470lbs.
50psi
19/32nds
7-8.5"
NA
10.7"
NA
31.8"
NA

275/70PR17 C
2600lbs.
50psi
19/32nds
7-8"
NA
11"
NA
32.4"
NA

285/70R17 121P D
3305lbs.
65psi
20/32nds
7.5-9"
8.5"
11.5"
NA
32.9"
634

305/70R17 119P D
3000lbs.
50psi
19/32nds
8-9.5"
9"
12.2"
NA
34"
613

37X12.5R17 121/129P E
4080lbs.
65psi
20/32nds
8.5-11"
NA
12.5"
NA
36.7"
NA

40X13.5R17 121P C
3195lbs.
35psi
20/32nds
8.5-11"
11"
13.5"

39.8"
 

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Re: tow rigs and tire size:
I pondered this (2 yrs ago) for a while b4 I bought a new 2001 CTD/6spd 2500 4WD, and wound up with the 3.54:1 and NV5600. I was amazed at how dinky the stock tires looked on that 'way-up-there' chassis. I now have 68K miles on the truck, the last 10K were to Alaska and back with a Lance Lite camper on the back. Before the trip I had 285-16 BFG AT/KO's installed. The traction, clearance and off-roadability were improved over the stock 245-16 Mich. E rated truck tires that came with it. I found that if you go over the 285 size, you run the risk of tire rub (on the front) and will have a hard time using chains as the clearance, especially on the front fenders is tight.
I am very dissapointed with the longevity of the AT's. After only about 11K miles, they're about 3/4 gone. One also blew on one of those long lonely gravel roads north of the Arctic Circle. [We drove over 2500 miles on dirt and gravel roads] They're 'D' rated, 33xx lbs. per tire, actually more than the E rated tires (3250) they replaced.
To the point, I find the 32.9" tire (the 285's), 3.54:1, 6speed, Cummins with 2000 lb. camper flat towing my CJ8 to be just right. Honestly, on the trip to Alaska we averaged 75-80 mph on much of it, and the gearing, power, and flexibility, up or down hill was just fine. Some of the intermountain roads I was down in 5th gear (1:1), but it still seemed like the right gearing for the situation and I wasn't making black to do it. At an adjusted 55pm i'm turning 1600 rpm. At 75 it's about 2150 rpm. The sweet spot seems to be between 1900 and 2100 rpm.You wouldn't be doing that speed with 4.10's unless you had much larger tires, which wouldn't fit.
With the camper, the rig is around 9500lbs, loaded. Add a 4100 lb towed CJ8 for an under 14K lb. gross lashup.
IF...I were towing big-time (18K-20K lb. GCVW) I would opt for the 4.10's and just stay in the slow lane, and stay away from an automatic.
regards, as always, jefe
 

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so mine are 315 70 17s. However they figure it, they measured 34.5 x12 ish unmounted.
It works out perfectly!
315+25.4=12.4" of width

12.4x70%=8.68" of sidewall height

8.68x2=17.36+17(wheel)=34.36" tire height

Amazing it actually works out right as opposed to all the
discrepencies in 37s, 38.5s and 40s that the various
manufacturers sell for our rigs!

Kent
 

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Jefe,

I was considering that very tire for my Dodge. What do you attribute your lousy mileage to? Do you know of a 285 that gives better mileage while still delivering performance?

I know with mine I only got 32K miles on my OEM Michelins and now have about 17K on a set of Firestones which a buddy took of his Powerstroke and they're almost shot. I think the Cummins, when turned up a little just tends to eat rear tires for lunch!

Kent
 
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