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2001 2500HD gearing question

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  • 2001 2500HD gearing question

    First off, let me say hello as I am new to this forum. My question for yall is: I have a 2001 Chevy 2500HD with the 6.0L and 4.10 gears. It has 305x70x16 tires on it right now and is pretty sluggish when towing heavy loads. The 4.10 gears were factory and I was wondering if I should upgrade the gears to 4.56 or 4.88 to compensate for the increased tire size. By the way, original tire size was 245x70x16 (not sure about the 70 part).

    Thanks in advance,
    Wes

  • #2
    Anything over a 4.10 will really raise your RPM on the highway. A 305/70 isnt that big of a jump in tire size. If you tow A LOT.....and done mind the higher RPMS on the hiway, go ahead and re-gear with 4.56's. But 4.88's are way to steep for that small of a tire.
    2007 Silverado Classic, Crew Cab, Eagle 079, Magnaflo, Airraid and BB Tune.
    2001 Silverado HD, 6" Rancho Lift, 16x10 Eagle 102's and 36x14.50x16 STS's, Rancho Traction Bars. SOLD

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    • #3
      Re: 2001 2500HD gearing question

      Originally posted by Chevytuff19
      First off, let me say hello as I am new to this forum. My question for yall is: I have a 2001 Chevy 2500HD with the 6.0L and 4.10 gears. It has 305x70x16 tires on it right now and is pretty sluggish when towing heavy loads. The 4.10 gears were factory and I was wondering if I should upgrade the gears to 4.56 or 4.88 to compensate for the increased tire size. By the way, original tire size was 245x70x16 (not sure about the 70 part).

      Thanks in advance,
      Wes
      Go ahead, slap in the 4.56's and you will not be sorry. Those big tires take their toll on gearing and 4.56 would put to back it line and with OD there well be no MPG issue as many claim. I would not generally recommand 4.88 in a high use truck that may se a lot of miles as that gear ratio set has less pinion to ring gear contact area than a 4.56 or 5.13 due to gear tooth counts for than combo.

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      • #4
        I thought 4.88 gears seemed excessive, but then again it seems like the overdrive drops more rpm's than in Z71s and other trucks. Also, the first gear in my 2500HD seems a little overgeared and will easily pull the truck all the way up to 45-50mph. That just seems like a lot longer pull than you would expect from a 3/4 ton pickup.

        So the concensus would be go with 4.56 gears to improve towing?

        Thanks,
        Wes

        Comment


        • #5
          Originally posted by Chevytuff19
          I thought 4.88 gears seemed excessive, but then again it seems like the overdrive drops more rpm's than in Z71s and other trucks. Also, the first gear in my 2500HD seems a little overgeared and will easily pull the truck all the way up to 45-50mph. That just seems like a lot longer pull than you would expect from a 3/4 ton pickup.

          So the concensus would be go with 4.56 gears to improve towing?

          Thanks,
          Wes
          Most definatly. It will also put truck engine back in power better at any given speed. You did not say how heavy your tow is but if it is around 8000lbs or more you might do 4.88's . I know it sounds deep but we used to run 4.10's and 4.56's in trucks with 30 to 32 inch tires 25 years ago without OD trannies. They would tow like crazy too! I could pull heavily loaded 4 horse trailers up the steep grades on the interstates that I encountered and hold speed with little trouble too with them gears back then.

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          • #6
            Ok, so that is what I am going to do. Also, I was never quite sure about one other thing: When you put the gear shifter in "D" and have the tow/haul button on, does it disengage overdrive?

            Thanks again,
            Wes

            Comment


            • #7
              Originally posted by Chevytuff19
              Ok, so that is what I am going to do. Also, I was never quite sure about one other thing: When you put the gear shifter in "D" and have the tow/haul button on, does it disengage overdrive?

              Thanks again,
              Wes
              Wes

              As a rule of "thumb" it is best to leave tranny in drive when towing but you can use a little common sense here too and use OD some with 4.56's if load is not to big or ground is pretty flat. Just kinda feel it out a bit and find where it is happy. Never "lug" engine hard towing in OD though.

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              • #8
                Originally posted by Chevytuff19
                I thought 4.88 gears seemed excessive, but then again it seems like the overdrive drops more rpm's than in Z71s and other trucks. Also, the first gear in my 2500HD seems a little overgeared and will easily pull the truck all the way up to 45-50mph. That just seems like a lot longer pull than you would expect from a 3/4 ton pickup.
                The Z71 trucks you are referring to have a 4L60-E trans. The overdrive ratio in those is 0.70 to 1. The transmission in your truck is a 4L80-E which has an overdrive ratio of 0.75 to 1. So, your are correct - overdrive drops RPM more in Z71 trucks. The Hydramatic 4L80-E is a close-ratio heavy duty 4-Speed. Part of the reason it was designed that way is because it was intended for use on high-torque low-revving bigblocks and diesel engines that do not have the RPM range that your 6.0 is capable of. Your first gear is 2.48:1. The 4L60-E in the Z71 has a first gear ratio of 3.059:1 which is a lot deeper. The ratios in the 4L60-E are actually a better match for your engine but the 4L80-E handles much more power and is more appropriate for your class of truck.
                "James B." '99LT_Tahoe4Dr2WD, Tuned L29 Vortec 454, 62#Injectors, MSD6A, Six 3"mufflers, 10.5"non-float14bolt ,EatonPosi, 4.56:1, Built4L80E, Gear_Vendors, Splined_Driveshaft, HydroBoost, Be-Cool_Rad., FAL-292fans, Tracbars, Swaybars, AirRide, etc.

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                • #9
                  In light of James B.'s new info about the ratio of my transmission, I might opt to go with 4.88 gears. That would put the power curve about on par with a stock Z71, correct? I knew I should have coughed up the money for the diesel.......oh well though. My heaviest load will probably be about 9000 lbs. if that makes a difference.

                  Thanks once again,
                  Wes

                  Comment


                  • #10
                    Originally posted by Chevytuff19
                    In light of James B.'s new info about the ratio of my transmission, I might opt to go with 4.88 gears. That would put the power curve about on par with a stock Z71, correct? I knew I should have coughed up the money for the diesel.......oh well though. My heaviest load will probably be about 9000 lbs. if that makes a difference.

                    Thanks once again,
                    Wes
                    It will put you a little better than stock in performance. If you are looking at up to 9000lbs with them tires, go with 4.88 then. I know they make them for the front (Precision and Yukon) and you will hav to check which pig you have it back (might be a 11.5) to check ratio availiblity. It should give you about 2200 RPM at 60 in OD which is about right for that big heavy truck and tire combo.

                    BTW GM could gear 4L80E lower in first (about 2.8 or 2.9 if they wanted too) but then nobody would need to buy Allison then with a gasser.

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                    • #11
                      When you put the bigger tires on did you get the computer recalibrated for the bigger tires? If the stock computer is still thinking it has 245's instead of 305's the truck will definatly feel down on power..... When I was workin at one of the dealer's, I reprogramed a guy's truck for 285's. Just checkin....
                      77' GMC 3/4 ton 4x4 4"susp, 3"body, 36" swampers, 450hp 406, 4L80-E, 205..... nice import.... wanna race.... ???

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                      • #12
                        Anyone know what kind of rear and front axle came on a 2001 Chevy 2500HD 4x4 w/ 6.0L V8?

                        Thanks,
                        Wes

                        Comment


                        • #13
                          Originally posted by Chevytuff19
                          Anyone know what kind of rear and front axle came on a 2001 Chevy 2500HD 4x4 w/ 6.0L V8?
                          Should be a Semi-Float 9.5" 14-Bolt with 8-lug axles.

                          Looks like this:
                          http://www.drivetraindirect.com/html2/gm95.html
                          "James B." '99LT_Tahoe4Dr2WD, Tuned L29 Vortec 454, 62#Injectors, MSD6A, Six 3"mufflers, 10.5"non-float14bolt ,EatonPosi, 4.56:1, Built4L80E, Gear_Vendors, Splined_Driveshaft, HydroBoost, Be-Cool_Rad., FAL-292fans, Tracbars, Swaybars, AirRide, etc.

                          Comment


                          • #14
                            They apparently don't even make 4.88 gears for my truck.......anyone know where to find some?

                            Wes

                            Comment


                            • #15
                              Originally posted by James B.
                              Should be a Semi-Float 9.5" 14-Bolt with 8-lug axles.

                              Looks like this:
                              http://www.drivetraindirect.com/html2/gm95.html
                              It will be a 9.25 in the front and either a 14 bolt 10.5 or 11.5 AA rear axle.

                              Originally posted by Chevytuff19
                              They apparently don't even make 4.88 gears for my truck.......anyone know where to find some?

                              Wes
                              Where have you looked and you need to confirm which rear axle you have. The front is no problem.

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