New here...Do I Need to regear for 35's with 3.73 gears

[Aftershock00]

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 transmission.

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 transmission 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.

 

[diesel_driver]

Welcome to the TDR!

I have asked the same question. I have a 2004 SB 3500 4x4 with the HO and auto trans, and I'm switching to 35's in the next couple of weeks. I just rebuilt the complete front end with new ball joints, bearing/hub assemblies, and axle u-joints. Next to go on are 3" springs and such. I'm really thinking about switching to 4.10's. I'm hearing both, "...it will be fine...", and "...you'll hate it if you don't lower the gearing." I think that I will start buying the necessary special tools, and then make the switch to 4.10's. I figure that way, if I ever get a wild hair to run 37's, although 4.10's would still be a little high, it would be acceptable.

 

[Bob4x4]

Driving in the flat lands will allow you to get by with higher gearing.35's and 3.73;are not ideal but with light occasional towing will be ok.The 6 speed auto allows you to downshift with a slight increase in rpm without loosing much roadspeed

 

[cerberusiam]

That tire should be a little under 34" installed so it should be a good match for light towing and the 6 speed transmission. About as close as you can come to a balance between enough tire for efficiency and not totally kill the power band. You can fix the power and trans operation with a programmer if desired, you should be fine.

 

[Aftershock00]

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, but it's definately acceptable performance wise with the 35's.... And I didn't even put the bullydog tune in.

Mia's far as a tune, I'm wondering if the tune will let me expand the shift points. I don't know if the transmission shifts based on wheel speed or axle speed, but my only concern is that the transmission 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

 

[cerberusiam]

If you had 35's you probably would not like it, but, that is a personal preference and no one is going to tell you positively you will like it or not because you would likely complain the opinion wasn't what you thought it was. All anyone can do is tell you it will likely be fine because we aren't driving your truck the way you do.

Of course the trans shifts are going to be off because the speedo is off, you will have to fix that first then drive to see if you like the performance. If you get a capable programmer you will be able to tune the transmission shift points to your liking, until then it won't feel right.

 

[Motorhead]

I don't know if the 2008 can have the speedo re-programmed like the 2007, 5.9 can with a Smarty Sr or JR but it is easy with that programmer. I put a set of 33.85" tires on my '07, 5.9 and I like it on the road unloaded to mid loads. With my 5th wheel, I prefer to put my stock 265-70-17 back on. My truck is the late G-56 with the .74 6th. The BIG advantage YOU hve with your 68rfe is that you have two overdrive ratios in 5th and 6th. Your 4th is 1 to 1, 5th is .82 and your 6th is .63 so you can easily tow with oversized tires and just stay in 5th. With my G-56 I am either in 5th which is 1 to 1 or 6th which is .74.
While you might want a standard trans, I think for over sized tires, you have the better deal with the 68RFE. I love my G56 but I wish someone would come up with a stand alone transmission control that would interface with the 5.9 ECM so if I wanted to convert to a 68RFE or AISIN 6 speed, I could.

 

[mfurrh55]

When you get your bulldog programmer you can adjust your speedo with your tire size, I did, good luck and God bless, Monte

 

[Aftershock00]

When you get your bulldog programmer you can adjust your speedo with your tire size, I did, good luck and God bless, Monte

When the bullydog adjusted the speedo did it improve or worsen the shift points? My worry is that if shift points are based on speed, it is going to shift even earlier since it essentially thinks is going 5mph faster curre currently. I was almost thinking that adjusting to an even lower tire size would make it wins the gears out a little more.

God bless.... 'Murica!

 

[cerberusiam]

Shift points are driven off of wheel speed, load, and throttle percentage. With a capable programmer you can adjust all those. You need to adjust the pinion factor to correct the speedometer. Easiest way to do that is with a GPS app on a smart phone or a GPS unit. It won't be perfect as there is an error factor in GPS but it will get you close enough.

 

[sag2]

Be careful what you wish for with a manual transmission. I have met with too many owners that thought the truck didn't have any power and thought something was wrong. With the auto you have a great advantage over the manual because you have torque multiplication going on in the converter. Off the line the auto will smoke the manual all day long. The engine will be just as happy at 1500 as 1800 and you can't hurt it, but it may not be in the sweet spot for fuel economy if your worried about that.

 

[cerberusiam]

I have met with too many owners that thought the truck didn't have any power and thought something was wrong. With the auto you have a great advantage over the manual because you have torque multiplication going on in the converter.

There is something wrong, the engine is detuned because the clutch cannot handle the TQ and the transmission is suspect under high TQ loads. Bring it up to the auto power level and bye-bye DMF, hello Southbend.

The TQ multiplication in the TC is the single biggest POS part of the converter, main reason why the stocker is a boat anchor. Small boat at that. I know WHY they did it, but, that doesn't change the fact it is a POS design.

 

[Motorhead]

The 325hp, 610 torque, 5.9 engine was used with both the automatic and the G-56. How was the standard trans engine detuned? Granted, the DMF clutch was a disaster.

 

[cerberusiam]

Not the 6.7's, the autos got more HP and TQ.

 

[Motorhead]

You're right..Thinking about the 5.9 and not the 6.7. Sorry.

 

[Aftershock00]

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. Not the best pic, but here she is...

#ad

 

[Bob4x4]

What other people do has very little to do with it.I run 37's and 35's both sizes are heavy,the 37's weigh a good bit more than 35's.There is a fuel penalty running the 37's even with the 4.10 gears I have.The 35's are better for responsiveness and towing but the 37's are better off road

 

[cerberusiam]

No 34.84 is not 34.84 mounted on the rim and truck. If it runs as most of them do it is probably 33.8 or maybe close to 34, have to measure it. With the 6.7 that should be as close to a balance of power and efficiency as you can get. Without a tuner and recalibration it won't feel right as major parameters are off.

 

[Aftershock00]

No 34.84 is not 34.84 mounted on the rim and truck. If it runs as most of them do it is probably 33.8 or maybe close to 34, have to measure it. With the 6.7 that should be as close to a balance of power and efficiency as you can get. Without a tuner and recalibration it won't feel right as major parameters are off.

Ok ok well I understand the concept you're talking about BUT, the nitto website states that 34.84 is the Inflated tire diameter... So I guess not inflated they are 35.4 or something.

Looking forward to that bullydog gt coming in the mail. Hopefully, that'll complete the equation of balance of power and efficiency

 

[cerberusiam]

Uh huh, the Nitto web site says mine are 34.2, they measure MAYBE 33.1 installed. There is not one metric tire that has ever measured installed what the diameter claimed, and I have been thru a few. They measurements they give must be on the narrowest rim listed and at full pressure with no load. When you start inputting tire size to correct speedo to GPS then it becomes obvious something is off. I have to run 32.6 tire size to get the speedo within 1 mph of GPS.