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wmoses's avatar
wmoses
Explorer
Jul 12, 2013

Anyone changed their rear end for more towing capacity?

I am considering upgrading my RV to a TT that as a GVWR of 7500# which is about 500# above my TV rated capacity.

I have a 3.08 rear end and from what I can gather, a similar truck as mine with the 3.42 rear end has a tow capacity of about 9500#. Rather than buy a new truck as well as new RV, I was considering changing the rear end gears.

Has anyone here done this and what is involved?

I asked my GMC dealer for a quote which they gave, but they also said (and the Rep confirmed) that even if they changed the rear end it would void my power train warranty. They also sounded reluctant to do the change. I have 42k miles on the truck and I believe 4 more years of extended warranty left.
Tow Vehicles

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  • carringb's avatar
    carringb
    Explorer
    Jul 12, 2013
    Changing gear ratios will not void your powertrain warranty as long as you stick with a ratio offered by the factory. Since warranty coverage is a concern, do not use an aftermarket programmer to adjust the speedo. Dealer now look for that if anything goes wrong. Instead, either go to the dealer or any independent repair shop with a "GM TECH-2" terminal and they can do the programing, if it even needs it (many trucks use the rear diff speed sensor, which won't be affected by a ratio change).
  • docnascar's avatar
    docnascar
    Explorer
    Jul 12, 2013
    I would also venture to say, ensure you have an adequate trans cooler. Your rpms will make a jump up.

    I'm in a similar boat, my 2010 silverado truck has a max rating of 4700lbs with 3:23 rear. Trucks with 3:73 takes it to 6700lbs.
  • the_bear_II's avatar
    the_bear_II
    Explorer
    Jul 12, 2013
    There may be more to the "a similar truck as mine with the 3.42 rear end has a tow capacity of about 9500#." specs than just different gearing. The axles may be stronger, bigger brakes, higher capacity springs, different shocks plus auxillary cooling and more.

    When I was shopping for 3/4 ton trucks the gearing, brakes and springs were different from the factory for the higher tow capacity truck vs. the lower capacity version of the same truck.

    That may be the reason the dealer would warn about voiding your warranty. You may need to add more to match the 9500# truck.
  • APT's avatar
    APT
    Explorer
    Jul 12, 2013
    If you want to change, see if there are any 3.73 or 4.10 out there. They cost the same and labor is at least much as parts. Do it right once. GM only offers 3.08 and 3.42 in that differential housing, but aftermarket may offer more.

    Most people that change gearing go at least 2-steps. So, 3.08->3.73. You will need an aftermarket engine/trans tuner as well.
  • retispcsi's avatar
    retispcsi
    Explorer
    Jul 12, 2013
    You can change gears and it will make a difference. The other question or questions you need to consider concern your total weight. If the TT has a 7500# limit what will it weigh when you load it with all of your gear etc. How much do you put in the TV, people, firewood etc. I don't know the towing specs on your TV but take a minute and look at the total unit truck and trailer and examine if you have enough truck to handle the load. Good luck.
  • The_Texan's avatar
    The_Texan
    Explorer
    Jul 12, 2013
    Buy the OEM 3.73 gears off the internet, have a reputable automotive garage do the change and GM will never know the difference. Yes, it will make a difference in how it does the job, but it will still be a 5.3 pulling a heavy load. I am very happy with my 6.2L NHT pulling 10K, so it will do the job.
  • ReneeG's avatar
    ReneeG
    Explorer
    Jul 12, 2013
    BurbMan wrote:
    If its 4WD you'll need to change both axles. Forum member crappiefisherman changed the axles on his V-10 Excursion from 3.73 to 4.30 and it made a big performance difference towing in the mountains out west.

    In your case, a 3.08 rear axle is really high....3.42 is better, most "tow" vehicles are 3.73 or 4.10 but not sure that you need to go that low with a 6 speed transmission.


    In our previous TV, a Ford F250 V10 4WD, we changed out the rear end from 3.73 to 4.3. It made a difference in towing our 11K TT at that time. We tow a lot in the mountains. Yes, we had to change out both axles.
  • beergardens's avatar
    beergardens
    Explorer
    Jul 12, 2013
    It will make a big improvement on how your truck pulls the trailer. If you do it, I would consider making a bigger jump, to 3.73 or maybe even 4.10, to make a bigger improvement.
  • BurbMan's avatar
    BurbMan
    Explorer II
    Jul 12, 2013
    If its 4WD you'll need to change both axles. Forum member crappiefisherman changed the axles on his V-10 Excursion from 3.73 to 4.30 and it made a big performance difference towing in the mountains out west.

    In your case, a 3.08 rear axle is really high....3.42 is better, most "tow" vehicles are 3.73 or 4.10 but not sure that you need to go that low with a 6 speed transmission.
  • Emptypockets's avatar
    Emptypockets
    Explorer
    Jul 12, 2013
    I had this done years ago on a 1/2 ton Dodge - if two wheel drive it is a simple ring gear & pinon change out, expensive but a simple change. The rest of the story: after I had the change made it didn't change the fact that my pickup was still not up to doing the job.

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