Jump to content

3.73s

M1ck3y

By M1ck3y
in Modifications, Wheels & Tires

 Share

Recommended Posts

KARNUT Senior Enthusiast

KARNUT

Posted
Posted

 I did that often with the cars my wife drove. She would drive mostly in town. The acceleration would pick up and the in town fuel mileage would increase. Later with trucks if they didn’t already come with 373s or 410s I would change them. My trucks early on would carry weight in the bed or pull loads. We would add gear vendors in some. Today with the transmission and final gear combo unless you’re messing with over sized tires. I don’t know if it would be necessary. It much easier to buy the combo to fit your needs. 

  • Like 3
M1ck3y Senior Enthusiast

M1ck3y

Posted
  • Author
Posted (edited)

3.23, 33” tires, 4wd. Looking for improvement in acceleration..

Edited by M1ck3y
  • Like 2
garagerog Enthusiast

garagerog

Posted
Posted

If you have the 8L90 with 7th and 8th OD ratios, I would be tempted to go with the 4.10 ring and pinion set especially if you occasionally load or tow heavy. The 3.73 will be a huge improvement over 3.23, but with the expense of 2 differentials, you don't want to be left just wanting a tad more. Besides, I see gas prices being stable for the foreseeable future.

  • Like 2
M1ck3y Senior Enthusiast

M1ck3y

Posted
  • Author
Posted
5 hours ago, newdude said:

When you say 33" tires, are they floatation size?  What size are they?  


They’re 285/65r18. Sidewall says 33”, tire Calc will say 32.6”

  • Like 1
M1ck3y Senior Enthusiast

M1ck3y

Posted
  • Author
Posted (edited)
7 hours ago, garagerog said:

If you have the 8L90 with 7th and 8th OD ratios, I would be tempted to go with the 4.10 ring and pinion set especially if you occasionally load or tow heavy. The 3.73 will be a huge improvement over 3.23, but with the expense of 2 differentials, you don't want to be left just wanting a tad more. Besides, I see gas prices being stable for the foreseeable future.


Yeah I was thinking 4.10s, maybe even 4.30s max. Problem is 3.73s is the max size for 9.76 and the shop I’m working with won’t do a gear kit that has a spacer (to fit a larger gear).

Edited by M1ck3y
  • Thanks 1
swathdiver Senior Enthusiast

swathdiver

Posted
Posted
On 9/22/2025 at 7:59 PM, M1ck3y said:


Yeah I was thinking 4.10s, maybe even 4.30s max. Problem is 3.73s is the max size for 9.76 and the shop I’m working with won’t do a gear kit that has a spacer (to fit a larger gear).

You can change the carrier to run a lower gear.  The carrier you have is only good for 3.23 and lower (numerically) and the other one is good for 3.42 and higher.

  • Like 1
swathdiver Senior Enthusiast

swathdiver

Posted
Posted

Here are your effective ratios and rpms at speed as configured now:

 

image.thumb.png.11d24cc4df38b6e8db9db8a831a56bba.png

 

3.42s:

image.thumb.png.31b738330419be943ad82d7d184020eb.png

 

3.73s:

image.thumb.png.6a1e8d8673a1cf9bf77699b97f65ebc2.png

 

4.10s:

image.thumb.png.41020df38f9f8733bad3454449016e3f.png

 

4.30s:

image.thumb.png.828977308aa539743031ecaf54d982a3.png

 

https://demandaam.com/expview/976-RearAxle-Salisbury-12Bolt

 

The Ram with the 5.7 Hemi and ZF 8-speed transmission can come with 3.92 gears.  You're equivalent would be 4.10 gears.  So, it's not too much 1st gear as some say.  Those trucks leap off the line at the track like nobody's business.

  • Like 2
  • Thanks 1
M1ck3y Senior Enthusiast

M1ck3y

Posted
  • Author
Posted
8 hours ago, swathdiver said:

You can change the carrier to run a lower gear.  The carrier you have is only good for 3.23 and lower (numerically) and the other one is good for 3.42 and higher.


Any thoughts on how changing gears will affect the driveshafts critical speed? 

  • Like 1
davester Senior Enthusiast

davester

Posted
Posted

The driveshaft's critical speed (in rpm) will not be changed.  What changes is how fast the vehicle is going when the driveshaft is going at that rpm.

 

A lower gear ratio (3.73 for example), you will be going faster for a given driveshaft speed/rpm, vs a higher ratio (say 4.10).

  • Like 2
M1ck3y Senior Enthusiast

M1ck3y

Posted
  • Author
Posted
3 hours ago, davester said:

The driveshaft's critical speed (in rpm) will not be changed.  What changes is how fast the vehicle is going when the driveshaft is going at that rpm.

 

A lower gear ratio (3.73 for example), you will be going faster for a given driveshaft speed/rpm, vs a higher ratio (say 4.10).

 

Right, I’m wondering how much my top speed will drop after changing gears…

  • Like 1
GETGONE Enthusiast

GETGONE

Posted
Posted

Unless you're tuned it won't matter anyways since it's electronically limited to 112mph.

  • Like 1
davester Senior Enthusiast

davester

Posted
Posted

Actually, you would get a different top speed just changing the gear ratio, because most GM trucks have the VSS at the rear of the transmission or transfer case, so the ecm miscalculate the speed the truck is going, and the limit it applies will similarly be off.  Tuning the truck to fix the speedo would then return it to the 112 limit, unless the limit is also changed as part of the tune.

  • Like 2

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.5k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,902
    Total Members
    8,960
    Most Online
    whenindoubtuseahammer
    Newest Member
    whenindoubtuseahammer
    Joined

  • Who's Online   3 Members, 0 Anonymous, 309 Guests (See full list)

  • Latest Articles

  • Posts

    • Coastie05
      Casey from the Texas Hill Country

      By Coastie05 · Posted

      Enjoy the new truck, it’s a beauty. I’m glad you’re keeping the OBS, I love those old trucks. 
    • chris21
      Towing In Loose Gravel

      By chris21 · Posted

      With large equipment or deep mud it is more of a use the higher gear to avoid spinning tires, getting stuck because of spinning tires and doing damage to your machine. The idea is if you run out of torque before you spin tires you can still downshift for more torque. If you are just spinning your tires in the lowest available gear you are stuck and things break.   Automatic transmissions, traction control and electronic transfer cases change the calculation a little as you the driver have less control over each piece. 
    • davester
      My First Project and GMC has me stumped

      By davester · Posted

      are there any codes? with lots of rust, perhaps disconnect/clean both sides of the connection/examine cable ends (the wires) for corrosion going into the sheath & replace if necessary/reconnect ALL the power AND ground cables between the battery, engine, frame, cab, fuse box and starter charm.li (website) has a no-start diagnostic procedure you can work through to get it working.
    • Chuck FB
      OCI, not when but why?

      By Chuck FB · Posted

      Its no wonder you've gravitated to the oil types and brands you have in later years after trying certain brands and one being a specialty oil or at least very hard to come by up here and the other would have been a commonly found oil of the era and the vastly different outcomes as a result to using the vehicles in question the same distance for an OCI . It shows what marketing hype can do without actually having the product to back up the claims and that is no different now with the insane claims that are written on the side of a bottle of oil from some of the off the shelf oils.    What has surprised me and I was already finding this out before I bought my truck with the GDI engine, that this newer fancy technology that seemingly would suggest better fuel economy/emissions with this high pressure spray of fuel is not in reality kind at all to the engine or at least the oils life. Yet they insist on claiming long OCI with this technology just like they did with the port or similar type fuel injection systems when in reality its a step back in oil life to have a GDI system.    I think the mistake your making Grumpy is that your not sending your samples to Blackstone and getting the feel good glowing report that you can run it another 1000 or more miles and then send another sample where they say run it yet another 1000 miles and on and on it goes until your sending in something that looks a lot like road tar and then they may suggest you change your oil within the next 1000 miles 😆
    • Chuck FB
      OCI, not when but why?

      By Chuck FB · Posted

      I am guessing that engines of that design back then had a better ability to be abused and survive longer than a new design engine with the long timing chain and the overhead cams and phasers etc. But I would never guess that an engine could go that far and not fail spectacularly or at least die a slow death. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...