Lifted what gear ratio??

What is your ratio

  • 3.21 with 8 speed

    Votes: 11 32.4%
  • 3.92 with 8 speed

    Votes: 11 32.4%
  • 3.55 with 6 speed

    Votes: 3 8.8%
  • 3.92 with 6 speed

    Votes: 1 2.9%
  • Other.. if running a different ratio post combo

    Votes: 8 23.5%

  • Total voters
    34

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Numerically higher gears are harder to fit in the diff because the ring gear gets really thick while pinion gear gets small. The max I could fit in was 4.56 because of this and the issues I ran into was the pinion bearings would wear out quicker probably because there was more heat with increased rpm. I had many issues from shops messing things up including the dealer. Had part of the carrier break off. It was a **** show. I got sick of it and it made me not like the whole decision to do it in the long run. That being said my Dad has almost the same pickup and the same stock 3.55s came in it and they went out around 100k as well so maybe it is just the 9.25 that is an issue not just when regeared. 33s to 35s is what I did and between that and towing I didn’t like the 3.55 and the 5/6 speed. I hated the down shifting when towing. It did okay in 4th and once the load was moving. 3.92 and 8 speed is very nice good on takeoff and nice riding on highway too. You can indeed use the calculator.

Thanks for clarifying. Is it common for a 4x4 to have 3.21? I'm reading that most 2WD have 3.21.
 

BWL

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I like to think that I will not be trading my truck in the near future. My goal was to keep it in the long run so I wanted to make sure I'm doing the right thing as I make modifications. Unfortunately, I was not educated on gearing when I bought the truck so I am stuck with a 4x4 and 3.21 gears.

It seems like there's a possibility to re-gear in the future. Question is, how long can I hold off while running 35s without compromising the life of the truck? I may be able to deal with the sluggish start as I do have a hybrid vehicle so Im used to it by now lol.
Shouldn't compromise the life of the truck at all. The bigger tires will speed up the wear on the front end. Ball joints, tie rods etc, but gear ratio won't affect that. Only thing that's compromised by the 3.21 is the durability of the diffs and they could still last the lifetime of the truck and some acceleration.
 
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Shouldn't compromise the life of the truck at all. The bigger tires will speed up the wear on the front end. Ball joints, tie rods etc, but gear ratio won't affect that. Only thing that's compromised by the 3.21 is the durability of the diffs and they could still last the lifetime of the truck and some acceleration.

I'm only doing a 2.8"bils and 1.5"readylift. I'm also be installing a heavier duty UCA from Zone.
When you mentioned "bigger tires", I am assuming the concern is the added weight? My stock is 33x10.8x20, replacing with 35x12.5x17. It should be lighter...so do you still see that being an issue?
 

BWL

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Wider tires and taller put more stress on parts. Lots of people running 35s get good life out of the front end. Just wont be as much as running stock.
 

WY-Dave

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Ahh gear ratios, went through this with my Jeep that I had. If ya'll don't mind I will pass on my experiences.

When you put on tall tires you are changing the effective gear ratio. Putting on bigger tires and keeping the same gears will reduce the engine RPMs at a given speed. Where I live I have to go through 20miles of rolling hills that there is a 1200ft changes. Towing the #1900 popup was a chore and usually got <10 mpg.

When I had 3.73 and stock 32" tires, I could not keep it in OD (6th) because at 65 the rpms were so low that the computer would drop it down a gear. When I went to 35s, it got worse. I put in 4.56s and all was good. My engine speed went up 400rpms. Because of it staying in OD, my mpg actually went up because stock the rpms were higher in 5th than modified in OD. Towing was vastly improved, I was pulling easy 15mpg towing. Now if I lived in flatlands, the opposite for mpg would probably would have been worse.

Here is a formula that if you change tire size it will give you the needed new gear ratio to keep the "performance" the same. If you want more grunt, go higher numerically. If you want better gas mileage, go down a step. In my Jeep example 3.73 with 35 was calculated out to 4.10s(4.08), I wanted a lil more umph when towing so I went a step up to 4.56.

Capture.JPG

With the current truck
http://www.4lo.com/calc/geartire.php
Capture.JPG

Here is a calc that you can change the numbers around to see mathematically how the mods would affect the engine speed. Trans Ratio is where you would put in the OD. For the auto Jeep was .80.

Current truck assuming .80 OD (just for example)
https://www.crawlpedia.com/rpm_gear_calculator.htm
Capture.JPG

Stock (3.42 & 33") 3.42=1811
With 35s @65mph and a .80 OD
3.42 = 1707 rpms
3.63 = 1812 rpms
3.55 = 1772 rpms
3.92 = 1952 rpms

Now I can't find my other calc that shows the affect on speedo from all the mods, but just putting on 35s will
change the actual speed @65 to 69mph (+6%) and 37s to 73mph (+12%).
They say, who ever they are, that a speed differential of > 10% needs to be reprogrammed for the affects on ABS & trans shift points.

So in the end if I wanted 35s, I would change gears to 3.55 (1772 rpms). For 37s change gears to 3.92 (1851 rpms) to keep the performance level the same.

Here is another link to full calcs from Crawlpedia
https://www.crawlpedia.com/calculators.htm

Capture.JPG
 
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Ahh gear ratios, went through this with my Jeep that I had. If ya'll don't mind I will pass on my experiences.

When you put on tall tires you are changing the effective gear ratio. Putting on bigger tires and keeping the same gears will reduce the engine RPMs at a given speed. Where I live I have to go through 20miles of rolling hills that there is a 1200ft changes. Towing the #1900 popup was a chore and usually got <10 mpg.

When I had 3.73 and stock 32" tires, I could not keep it in OD (6th) because at 65 the rpms were so low that the computer would drop it down a gear. When I went to 35s, it got worse. I put in 4.56s and all was good. My engine speed went up 400rpms. Because of it staying in OD, my mpg actually went up because stock the rpms were higher in 5th than modified in OD. Towing was vastly improved, I was pulling easy 15mpg towing. Now if I lived in flatlands, the opposite for mpg would probably would have been worse.

Here is a formula that if you change tire size it will give you the needed new gear ratio to keep the "performance" the same. If you want more grunt, go higher numerically. If you want better gas mileage, go down a step. In my Jeep example 3.73 with 35 was calculated out to 4.10s(4.08), I wanted a lil more umph when towing so I went a step up to 4.56.

View attachment 157813

With the current truck
http://www.4lo.com/calc/geartire.php
View attachment 157815

Here is a calc that you can change the numbers around to see mathematically how the mods would affect the engine speed. Trans Ratio is where you would put in the OD. For the auto Jeep was .80.

Current truck assuming .80 OD (just for example)
https://www.crawlpedia.com/rpm_gear_calculator.htm
View attachment 157816

Stock (3.42 & 33") 3.42=1811
With 35s @65mph and a .80 OD
3.42 = 1707 rpms
3.63 = 1812 rpms
3.55 = 1772 rpms
3.92 = 1952 rpms

Now I can't find my other calc that shows the affect on speedo from all the mods, but just putting on 35s will
change the actual speed @65 to 69mph (+6%) and 37s to 73mph (+12%).
They say, who ever they are, that a speed differential of > 10% needs to be reprogrammed for the affects on ABS & trans shift points.

So in the end if I wanted 35s, I would change gears to 3.55 (1772 rpms). For 37s change gears to 3.92 (1851 rpms) to keep the performance level the same.

Here is another link to full calcs from Crawlpedia
https://www.crawlpedia.com/calculators.htm

View attachment 157818

Im saving your post so I can go back and review the formulas (haven't fully wrapped my head around it).

For me, I figured the following so far
Stock 33"x10.8"x20
New size 35"x12.5"x17
Gear ratio: 3.21

35 x 3.21 = 112.35
112.35 / 33 = 3.41 new gear ratio (ideally)

Now here comes my ignorance, 3.21 and 3.41 doesnt seems to be that far apart. Granted, 3.55 would probably be the ideal gear ratio for my truck but if I stay with 3.21, I dont see how much of an issue it really is.
Again, I'm not well versed into this so if anyone can correct me, please do. I'd greatly appreciate it.
 

WY-Dave

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Im saving your post so I can go back and review the formulas (haven't fully wrapped my head around it).

For me, I figured the following so far
Stock 33"x10.8"x20
New size 35"x12.5"x17
Gear ratio: 3.21

35 x 3.21 = 112.35
112.35 / 33 = 3.41 new gear ratio (ideally)

Now here comes my ignorance, 3.21 and 3.41 doesnt seems to be that far apart. Granted, 3.55 would probably be the ideal gear ratio for my truck but if I stay with 3.21, I dont see how much of an issue it really is.
Again, I'm not well versed into this so if anyone can correct me, please do. I'd greatly appreciate it.

@65mph & .8 OD
3.21/33 = 1700rpm slap on some 35s and 3.21/35 = 1602rpm and your speedo will be off by 6%. (65 speedo = 69 real). if you live in the flatlands and don't tow, you will probably not notice any driveablility differences. That -100rpm may be enough to have the truck gear searching when hitting hills. And if towing any real amount, you will be lugging the engine.

3.41/35 = 1702rpm (confirms the formula)
3.55/35 = 1772rpm

One thing to remember with the bigger tires you are adding weight. With my Jeep it was an extra 150# just from the tires. Now imagine steel bumpers, winch, body armor etc. With everything that was added, it gained about 900#. So re-gearing was a big deal.

To sum it up, terrain and use will be bigger factors that you would perceive as a win or lose. Flatland and no towing, no change. But hilly terrain and towing a 8-10,000 load, you would "feel" loss I bet
 
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@65mph & .8 OD
3.21/33 = 1700rpm slap on some 35s and 3.21/35 = 1602rpm and your speedo will be off by 6%. (65 speedo = 69 real). if you live in the flatlands and don't tow, you will probably not notice any driveablility differences. That -100rpm may be enough to have the truck gear searching when hitting hills. And if towing any real amount, you will be lugging the engine.

3.41/35 = 1702rpm (confirms the formula)
3.55/35 = 1772rpm

One thing to remember with the bigger tires you are adding weight. With my Jeep it was an extra 150# just from the tires. Now imagine steel bumpers, winch, body armor etc. With everything that was added, it gained about 900#. So re-gearing was a big deal.

To sum it up, terrain and use will be bigger factors that you would perceive as a win or lose. Flatland and no towing, no change. But hilly terrain and towing a 8-10,000 load, you would "feel" loss I bet

I was once told by a mechanic at a shop that there is a way to adjust the speedo with the new tires. I'm hoping the speedo will give me the accurate reading.

I expect my new set of wheels/tires to be -44 lbs lighter than stock

Adding approx +170 lbs weight (tonneau cover & N-fab RKR rails). Im not expecting under body armors and winch anytime soon (these will sit in my wishlist for a while)

I also live in a relatively flat terrain at sea level. On the rarest of occasion, I may tow a small trailer approx. 1,500 lbs but nothing heavier.

So,
New set of 4 wheels = -44 lbs. Other accessories = +170 lbs.
95% of driving on flat terrains
Light offroading and overlanding every once in a while.

Would you still re-gear to 3.55 if you were in my situation?
 
Last edited:

WY-Dave

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I was once told by a mechanic at a shop that there is a way to adjust the speedo with the new tires. I'm hoping the speedo will give me the accurate reading.

I expect my new set of wheels/tires to be -44 lbs lighter than stock

Adding approx +170 lbs weight (tonneau cover & N-fab RKR rails). Im not expecting under body armors and winch anytime soon (these will sit in my wishlist for a while)

I also live in a relatively flat terrain at sea level. On the rarest of occasion, I may tow a small trailer approx. 1,500 lbs but nothing heavier.

So,
New set of 4 wheels = -44 lbs. Other accessories = +170 lbs.
95% of driving on flat terrains
Light offroading and overlanding every once in a while.

Would you still re-gear to 3.55 if you were in my situation?

I would investigate the mechanic's claim alot more. I'm no expert in the '18+ and the new security stuff the factory put on to make tuning/config changes harder. I don't know if the dealership can change it or the only way is through the sec. bypass cable.

Anyway, Personally I would not spent the $2k plus for a regear.

Just seen this for programming
https://www.diablosport.com/2015-2019-ram-1500-hemi-tuning/
 
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I would investigate the mechanic's claim alot more. I'm no expert in the '18+ and the new security stuff the factory put on to make tuning/config changes harder. I don't know if the dealership can change it or the only way is through the sec. bypass cable.

Anyway, Personally I would not spent the $2k plus for a regear.

Just seen this for programming
https://www.diablosport.com/2015-2019-ram-1500-hemi-tuning/

Hm interesting...thanks for the advice. I'll also look into the link you sent.
 

crackerjack1957

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PC does not increase horsepower or torque........throttle response only
 

dearchristopher

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4” and 35mts with very minimal performance mods. 3.21 gears and I can break loose on dry pavement, tows great. around 15mpg city, highest i’ve seen is 19.5mpg highway, might get 20 now with the shell. doubtful.


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