35s & 4.30 Gears?

b2™ · Aug 24, 2014

Anyone running this set up? I'm thinking of ditching my 3.73s and have heard that 4.10s aren't worth the money to swap. Would like more towing power. I found this "chart" on another forum:

3:73's....................................4:30's
...stock tires.....35's.................35's........37's
MPH 
65..1900..........1750................2000.......1 850
70..2050..........1850................2200.......2 000
75..2200..........2000................2300.......2 200
80..2300..........2150................2400.......2 300

Does that look accurate?

true98jeep · Aug 24, 2014

I am running 4.56's on my truck with 37's it is almost exactly the same as the truck stock on the 32 inch tires and 3.73 from the factory. I did all the calculations and I am with-in 100-200 rpms difference at most at any speed. The 100-200 is slightly higher rpms meaning the truck is geared lower by a hair then stock. I would bet 4.30's and 35's would put you in the exact same range as me. I absolutely love it shifts spot on and ton';s of power and get up and go. I think running 75 I am around 2200-2400 been gone a month from home but I believe that is where I was at.

You can use these calculators to figure it all up it is what I used and it is spot on exact.
RPM Calculator
http://www.crawlpedia.com/rpm_gear_calculator.htm

Tire Size Conversion
http://www.crawlpedia.com/tire_size_converter.htm

Specs for the 5r110 to calculate RPMs in each gear
http://www.dieselhub.com/trans/torqshift-5R110.html

Hope this helps you. I absolutely love it would not second guess doing it all over again.

b2™ · Aug 24, 2014

Thanks for all that info! Looks like the 4.30s are going to be the ticket. Especially around town around 45-50. Right now it's constantly in and out of overdrive because the RPMs are around 1250-1300.

HeavyAssault · Aug 24, 2014

How heavy and how often are you going to tow?

b2™ · Aug 25, 2014

Up to 15k during the summer but mostly 8k worth through the mountains.

HeavyAssault · Aug 25, 2014

So what is your estimated cost for the gear swap?

b2™ · Aug 25, 2014

Hadn't checked but I'm assuming 1500-2k parts & labor.

HeavyAssault · Aug 25, 2014

I'd suggest something different than gears. Gears don't add power they simply change the mechanical advantage thru a different power/torque curve.

If you are sold on a gear swap I'd add something like a Tru-Trac or Detroit to that list.

b2™ · Aug 25, 2014

I know it doesn't add hp/tq, so pulling power may have been a poor choice of words. Especially towing in the mountains it's having to down shift a lot because it's not in it's power band. That's why I was looking into gears.

HeavyAssault · Aug 25, 2014

Is that using the Tow/Haul? I do agree most performance transmission tuning doesn't help in the hills. I did discover that my TSD SPD worked great in TH mode in the hills with my boat. On the flat roads I would turn off TH for better running RPMs. If I saw some hills coming up TH would be turned on then I would watch EGTs just as a safety measure. 15k is pretty heavy in all, 8k in the hills isn't easy either.

Hope it all works out for you.

b2™ · Aug 25, 2014

Yeah that was in T/H on stock tuning. I haven't tried my Gearhead tow tune yet but on SRL+ my RPMs are so low between 45-55 that it drops out of overdrive just driving around town. So I dunno if it will make that big of a difference going up those 8% grades in WV.

drunk on diesel · Aug 25, 2014

have Matt lock out OD in tow haul mode. then you can manually select 4th gear for going up hills

worth a shot and way cheaper than front rear R&P swap

b2™ · Aug 25, 2014

Didn't know he could do that. Might give that a shot.

drunk on diesel · Aug 25, 2014

I have him do it on all my tunes. He does it by default on his 6.4 tunes, but I request it on all my 6.0 tunes

Mdub707 · Aug 25, 2014

I like 3.73's with 35's. Couldn't imagine going to anything else. I tow ~7k lbs pretty often during the summer now. One of my buddies running on 40's took his 4.56's out in favor of his 3.73's. He didn't like the 4.56's at all. He said he would have went with 4.10's ideally for that, but he had the 4.56's in the truck and the 3.73's on the shelf so it was cheaper to just go back to those.

true98jeep · Aug 25, 2014

To each there own I guess. I absolutely love my 4.56's with 37's I just like having it shift and the transmission behave like it is 100% stock the day I bought it because that is what range that put me into. 95% of my traffic is around town so I don't mind turning 2200-2400 rpms going 75-80 in the truck when i am on the interstate. Do enjoy the fact that the 4.56's and the trutracs def take a ton of the strain off the transmission vs trying to turn 40's on 3.73's That is truly the biggest benefit to me taking the load off the tranny it gets beat on enough as it is. My fathers 350 dually had 4.10's from the factory and my truck is actually slightly higher geared than his stock.

b2™ · Aug 25, 2014

Flat land towing it does fine but in the mountains it sucks. Also the constant shifting in and out of overdrive in town between 45-55 is annoying. I can live with the uptown but I'll try Matt's tow tune and if need be get him to tune out o/d in tow/haul before shelling out for the gears.

speedracer1000 · Aug 27, 2014

i have 4.30s on 35s and tow heavy and have lots of hills. I honestly couldn't tell much of a difference as far as a seat of the pants feel. but I know it pulls better because it keeps the engine closer to its sweet spot in the rpms for torque. It did hurt my mileage some tho due to turning higher rpms all the time. but u r simply giving it more of a mechanical advantage. its probably just what your looking for.... as for power, ive seen first hand that a gear change especially on turbo cars ( don't see no reason for it to be different for a turbo diesel), say going with higher gears(lower number) such as from 3.73 to a 3.27 in a mustang will actually make the car much faster because u can run each gear out farther loading the turbo more. basicly just making the car work. its hard to explain wut im saying. that may be a relative issue as to why it didn't make my truck any faster per say.