Jump to content

re-gearing for 37's ??


Recommended Posts

People  !!! Front gear ratio change is not available for 2021 Silverado 1500 4X4.  So do not change rear ratio because you cannot change the front !!!. I learned the hard way after having my rear end done to 4:56 . We have contacted many axle rear end shops and they say " NOT AVAILABLE"  NOBODY KNOWS WHEN GEAR SET WILL BE AVAILABLE.. . My rear end is already geared to 4:56 so I am stuck driving truck with out front drive line while waiting for someone to manufacture front 4:56 gear ratio... My tires are 36"

Link to comment
Share on other sites

Just now, Alfred Padula said:

People  !!! Front gear ratio change is not available for 2021 Silverado 1500 4X4.  So do not change rear ratio because you cannot change the front !!!. I learned the hard way after having my rear end done to 4:56 . We have contacted many axle rear end shops and they say " NOT AVAILABLE"  NOBODY KNOWS WHEN GEAR SET WILL BE AVAILABLE.. . My rear end is already geared to 4:56 so I am stuck driving truck with out front drive line while waiting for someone to manufacture front 4:56 gear ratio... My tires are 36"

Any help would be greatly appreciated !!!

Link to comment
Share on other sites

  • 1 month later...

Rayo, there is no front gearing available as of yet. Rear gears are available but when my 4x4 shop  installed them and a Hypertech  speedo calibrator for the 4:56 rear gears my truck computer would not accept this change. there is no fix as of yet....I drive my truck in Tow/Haul mode all the time which really helps out but this is not a permanent fix.

Link to comment
Share on other sites

I believe with the front its not a simple ring/pinion swap you have to replace the whole diff. I don't know if the front diff is different on T1's or not, but with the k2's you can go up to 3.73.

 

For some reason I'm thinking the 3.0 diesel has 3.73s, so you should be able to. 

Edited by M1ck3y
Link to comment
Share on other sites

1 hour ago, M1ck3y said:

I believe with the front its not a simple ring/pinion swap you have to replace the whole diff. I don't know if the front diff is different on T1's or not, but with the k2's you can go up to 3.73.

 

For some reason I'm thinking the 3.0 diesel has 3.73s, so you should be able to. 

Take a look at your front diff.  About ten years ago GM went from the split diff style front IFS diffs they had been using to a more conventional (looks like a rear diff with a removable cover) diff.  I believe the ring gear changed then as well.

 

Starting in 2019, after the AAM Co rear axle vibration issue the 14-18 trucks suffered from, GM has started making their own axles again as well as using some AAM Co axles.  That's where the change is.

 

These axles can be regeared just like any other axle.  The aftermarket just hasn't started making gears for the front yet.  The rear axles are pretty much the same internally since 2014.

  • Thanks 1
Link to comment
Share on other sites

32 minutes ago, AJMBLAZER said:

Take a look at your front diff.  About ten years ago GM went from the split diff style front IFS diffs they had been using to a more conventional (looks like a rear diff with a removable cover) diff.  I believe the ring gear changed then as well.

 

Starting in 2019, after the AAM Co rear axle vibration issue the 14-18 trucks suffered from, GM has started making their own axles again as well as using some AAM Co axles.  That's where the change is.

 

These axles can be regeared just like any other axle.  The aftermarket just hasn't started making gears for the front yet.  The rear axles are pretty much the same internally since 2014.

 

Good info, thanks. So your saying the T1's use the same front diff as the k2's?

Link to comment
Share on other sites

I can't confirm that.  I do think that they must have changed something internally on the AAM Co made front axles since it seems like the ring and pinion from the 14-18 trucks won't work.

 

The new GM front axles are not supported by the aftermarket yet.

  • Like 1
Link to comment
Share on other sites

  • 4 months later...

I know this is an old post but since GM offers the 3.0 Duramax with 3.73's and someone like me who has a 6.2 with 3.42's and has gone up to 35's, going to 3.73's would make up for the tire size difference. (weight and wind resistance is a different story) but at least when towing my 10,000lb toy hauler I'd be slightly better off than where I am today. I'd rather go all the way to a 4.10 but with 3.73's my speedo would be extremely close and I could ditch the Hypertech inline corrector. Thoughts?

  • Like 1
Link to comment
Share on other sites

4 hours ago, jpfanner said:

I know this is an old post but since GM offers the 3.0 Duramax with 3.73's and someone like me who has a 6.2 with 3.42's and has gone up to 35's, going to 3.73's would make up for the tire size difference. (weight and wind resistance is a different story) but at least when towing my 10,000lb toy hauler I'd be slightly better off than where I am today. I'd rather go all the way to a 4.10 but with 3.73's my speedo would be extremely close and I could ditch the Hypertech inline corrector. Thoughts?

 

I'm in basically the same boat.  See this post in a different thread: 

 I'm actually in slightly worse shape, since my AT4 has factory 3.23 gearing.  I'm at (effectively) a 3.08 gear right now with 35" tires and the stock 3.23's.  The 6.2L and 10-speed trans DO make up for a lot, but 3.73's would get me pretty close to (effectively) stock 3.42 gearing, which is the same thing you're after (and should be perfect for my needs).

While I'm pretty sure rear axle ring/pinion sets are available aftermarket (my rear axle is an SU7; an AAM axle.  SU8 is the GM rear axle)... the big questions revolve around the front axle.  

Rumor has it that GM may be welding (or otherwise permanently attaching) the ring gear to the carrier in the front axles on these trucks.  If that's true (and I've heard it from more than one source) then that may be part of the reason the aftermarket doesn't seem to have any ring/pinion sets available (yet, anyway).

Now I'm not opposed to purchasing a whole front carrier (w/ring) and pinion directly from GM in 3.73 if that's the only way to do it right now, but that brings additional questions into play.  GM is using two different front axles on these trucks.  The SU5 (what I have) is a GM front axle.   And there's also an SU4, an AAM front axle.

 

So, if the 3.73 front ratio is only available with the 3.0L Duramax diesel, which front axle are they putting in those trucks?... and/or... are the internals (ring/pinion/carrier) interchangeable between the AAM and GM axle?  Because if ALL of the Duramax diesel 3.73 geared 4x4 trucks have AAM axles... and the internals are not interchangeable... then even trying to buy 3.73 front gearing direct from GM won't work for me (and my GM front axle).       

 

Just food for thought.  If you come up with a workable solution, please do come back and post it here (I'll do the same).

Edited by barr8888
Link to comment
Share on other sites

5 hours ago, AJMBLAZER said:

The front gears are not “welded to” the front carrier. That’s been disproven many times. There’s pictures around here to prove it. 

 

It's not my intent to spread misinformation... I'm only citing what I've personally been told by a GM dealership parts person... and have also read elsewhere. 

I acknowledge that it doesn't sound like something that makes any sense to me.  I don't see how the hardness of the ring gear itself could be maintained if any attempt was made to weld it, for one.

 I haven't taken the cover off my front axle to verify anything personally yet.  But finding reliable information and/or parts to change the front axle ratio has been much more of a challenge than I was expecting, so far.

Edited by barr8888
Link to comment
Share on other sites

1 hour ago, Byrds8 said:

What happens if you re-gear the rear but not the front?

You can’t use 4x4. The tires would be turning at different speeds front and back and as soon as they grabbed traction something would break. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Forum Statistics

    247.6k
    Total Topics
    2.6m
    Total Posts
  • Member Statistics

    336,349
    Total Members
    8,960
    Most Online
    Brian12345
    Newest Member
    Brian12345
    Joined
  • Who's Online   1 Member, 0 Anonymous, 692 Guests (See full list)




×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.