Is 3.73 safe for 35's with auto

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Aftershock00

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First of all... Yes I searched this forum and hours on Google. I have been stalking these forums for months but finally registered... I have no idea what took me so long.

I have an 08 ram 2500 ctd auto with 3.73 gears. It's my first diesel I bought off my father in law. It's in mint condition with 65k miles... Wish it was a standard tranny.

after researching the forums, I installed a 3" leveling spring and track bar from thuren, control arms from top gunz, extended away at links from and 1" block lift from tuff country in rear.
I also installed nitto terra grappler G2 285/75r18 which have a 34.8 diameter.


I am am meticulous with taking care of my vehicles and don't want to cause unnecessary wear. I had 33's on there but even with the crappy 2" leveling spring from rough country, the wheels looked like skateboard wheels in the wheel well.

Im happy with this setup and hope it's relatively practical on wear and tear items such as ball joints and u joints.

my long winded question to you guys is.... Do I need to regear to 4.10 if I want to avoid damaging or prematurely wearing my tranny and other drivetrain parts???

i don't really tow much, and when I do, it's either an open car trailer with a mustang on it or its dirt bikes and quads. So I'm not hauling 15k RV or anything like that.

i did notice a bit of sluggishness with the 35's from the 33's, but nothing that bothers me. What would and does bother me, is if I'm taking life off my truck and it's gonna be a clunky unreliable rat box soon because of these tires. The cheapest quote I got for gears front and rear was 2200.00. I'm in Long Island, ny... A crappy liberal state.

I I also ordered a bullydog gt for it but have not received it yet.

Any ny help would be appreciated to ease me mind one way or the other. I know 37's is a definite yes for gears but I also know there are inaccuracies with tire size such as people with 37's but diameter is 35.1, or 35's but diameter is 33.3.
My 35's are pretty much real 35"s.
thank you and sorry if this isn't the correct category... They all seemed valid in one way or another.
 

Ram444

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It has to be better than my 6.7 with 37's and 3:42's. I have the Aisin transmission that can't be tuned and it still does well but I'm running over 600hp and 1300+ ft/lb.
 

bulrid8

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4.11 would be ideal, but 3.73 are fine. Won't damage anything. Just loose mpg and have sluggish take offs.

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Aftershock00

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Thanks. I know 4.10s would bring it back to stock and would be considered ideal, but it's an 08 and I'd like to buy a new 2500 ram in a couple years, so I'm hesitant to drop 2k on gears on a 9 year old truck, as mint as it may be. If truck was a couple years old, I would most likely do it regardless
 

MADDOG

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I see no need to upgrade to 4:10's unless you need a torque improvement for moving a heavy load from a dead stop.

The 3.73's are used with lifted diesel powered trucks all over. You aren't straining it in the least with 35's.
 
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Aftershock00

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Thank you all for the replies!

Hey just to be clear, I already have the tires on, so it's not a question of whether I would be happy with it. I can say I'd probably prefer 4.10 if I had a magic wand, but it's definately acceptable performance wise with the 35's.

As far as a tune, I'm wondering if the tune will let me expand the shift points. I don't know if the tranny shifts based on wheel speed or axle speed, but my only concern is that the tranny seems to shift too early with the 35's, especially in 5th and 6th. Right now, I can do 65 actual speed at 1500 rpms in 6th. Speedo is about 4.5 mph off. Is that too low? I don't wanna lug the motor and strain crank, bearings etc. I also wonder if when I adjust the tire size in the programmer, is that just gonna make it shift even earlier???


My question is only if having 35's would put additional strain on the drivetrain and cause premature wear and or failure. I'd prefer if someone with actual knowledge on this topic answered rather than someone saying "you should be ok"
Thanks in advance for any replies
 

bulrid8

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Well, yes it will put additional strain and wear on drivetrain and suspension. The rotating mass of a 35" tire is more. Tranny can handle it, if you adjust Speedo to correct ratio. That will help the shift points and not cause excessive heat. Most wear will be in bearings, balljoints and tierods. You will just replace them more often.

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R.L.K.

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Better than my 3.55 s
 

justin13703

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Everything else being the same, the weight difference between 33s and 35s won't be much more than carrying a passenger with you all the time. Depending on what type of new tires you go with. Being a 2500 Cummins, honestly that truck won't even feel it.

Now if you start messing with offsets with new wheels, and make your wheels/tires stick out farther, you can start to see increased issues with bearings and components.

Technically, on paper, will adding any weight and rotating mass increase wear on things? Yes. Realistically, in the real world, the small difference between 33s and 35s on a 2500 Cummins will not cause you any issues. There is probably more of a weight difference between an empty tank and a full tank than there is between 33s and 35s.
 
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Aftershock00

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Ok thanks. I was asking more in terms of the gear ratio change that 35's would provide more so than the weight issue. I was not at all concerned about the rotational mass of the tires, it was the fact that 35's give me a gear ratio in the lower 3's.

When most people say they have 35's, is that a true 35"s or more like 34"?
 

justin13703

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The only real issue you will have with the ratio change will be your speedo being off a little bit, which can be fixed with a tuner. It won't have any negative affects as far as damaging components.

Most of the tires listed as 35s are going to be 35s. Some of the more aggressive ones, like trail grapplers, may even be a little bigger. I'd have to go actually measure mine to be completely sure.
 

usaf2006

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Mopar ran 37s on a concept truck with 3.55s. That was in a 1500 with a hemi. They said it ran okay lol, but I'm assuming mpg was garbage.
 
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Aftershock00

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Thanks guys. It's weird, when I look at the truck with the tires on it, they don't look crazy big or anything that would prompt this question. But hey, 34.84" is 34.84 inches... So I have to ask.

I always see Rams and HD ford with tires that look much bigger and wider. I wonder if they regear.

This is my truck...
 

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Aftershock00

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Hey guys, thanks for all the replies. So I have my bullydog gt installed and corrected the speedo. I still feel like 6th gear drops in way too early and 4th and 5th should wind out a little more during conservative driving.

Is there any way to make the tranny relearn when to shift? I know these trannies are less electronic than ford, but I'm still not feeling right about the lugging. Yes, I could just lock 6th out, and or use tow/haul mode, but I'd really like to have the truck drive normally without adjusting anything, Atleast when I'm driving without a load.
I was thinking of switching to 305/65r18 which is 33.6" tire according to nitto terra grappler g2. Maybe these would be the perfect combo of fuel efficiency and use ability. I really think 4.10 gears would solve my problem but I can't justify that kind of an investment on an 08, when I'm hoping to buy a 2018 when it come out
 

MADDOG

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Why not tune it?

4:10's will drop your MPG but will give you somewhat of a torque multiplier.

I take care of the lugging by not driving around town at slow speeds in full auto. The only time my truck hits full auto mode is when I am out on the freeway and in cruise control.

A programmer will firm up your shifting, you can set WOT shift points and it will help but in full auto, the trans will do what the trans is programmed to do.
 
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Aftershock00

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Well I have the bullydog gt. With the tire size adjusted, I'm doing 65mph at 1500 rpm.

I guess I can just get into the habit of locking out 6th unless I'm on the highway.

I had to set my tire size to 33.4 to get the speed to actually be accurate. Does that mean that my actual tire size is 33.4???

I just don't know if the truck will be all around happier going to the 33.6" tire. Might've that happy medium I am looking for. Truck looks great with the current tires that are 34.8 according to nitto tho. What's weird is that 35'sx12.5 measure 34.5 according to nitto. Not really sure how much half an inch affects gear ratio.

The heaviest thing I'd be towing is a mustang in an enclosed trailer so 7k pounds or so
 
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