3.73 to 3.42 gear conversion results request

[BHolm]

Just finished installing my GV OD last night, and I could not be happier. 70MPH is 1750 RPM in 6th with GV on. I was lucky and scored a new/never used GV OD for a really good price but in hinesight after driving the truck with it, I'd do it all over again even at full price!! It really transforms the truck into a highway cruiser, and will aid in towing my 28 ft tag too. I had a GV OD on my former '98 12V and loved it on that truck too. The difference on the 3 gen with early G56 is even more dramatic.

Am I correct in assuming the GV installs behind the t-case? That means you can't use it in 4x4. I'm not sure I am up for that compromise.



Is your G56 the taller OD(late ratios)? Heck I want those with the 3. 42s!

 

[BrianJ]

Am I correct in assuming the GV installs behind the t-case? That means you can't use it in 4x4. I'm not sure I am up for that compromise.



Is your G56 the taller OD(late ratios)? Heck I want those with the 3. 42s!

I can't think of too many situations where one would need both at the same time. If you are in a situation where you are cruising at a higher speed and want to utilize the higher gearing of the overdrive, odds are you are not going to need 4x4. Conversely, if you are wheeling' or in conditions (i. e. snow) where you need 4x4, odds are you don't need the additional gearing of the overdrive.



The GV unit hooks up to the ecm and will disengage when in 4x4 as protection for the overdrive.

 

[BHolm]

I can't think of too many situations where one would need both at the same time. If you are in a situation where you are cruising at a higher speed and want to utilize the higher gearing of the overdrive, odds are you are not going to need 4x4. Conversely, if you are wheeling' or in conditions (i. e. snow) where you need 4x4, odds are you don't need the additional gearing of the overdrive.



The GV unit hooks up to the ecm and will disengage when in 4x4 as protection for the overdrive.

I can think of several recent occassions where I would have liked both, that is why I brought it up. I76 to Neb and I80 all the way across around Christmas comes to mind. Straight roads, icy sections, need to make some time, like the added stability of 4x4. Keep in mind that even at 60-65 with the early G56 ratios, you are turning some rpms, more than I would like anyway.

 

[klenger]

I can think of several recent occassions where I would have liked both, that is why I brought it up. I76 to Neb and I80 all the way across around Christmas comes to mind. Straight roads, icy sections, need to make some time, like the added stability of 4x4. Keep in mind that even at 60-65 with the early G56 ratios, you are turning some rpms, more than I would like anyway.

Sounds like a good time to slow down, but that's just me.

 

[EEdmondson]

Sounds like a good time to slow down, but that's just me.

I agree!!!

 

[KBalzuweit]

I miss my 6 speed Allison more and more every day! Its getting old turning 2200rpms @ 70mph!

 

[BHolm]

Sounds like a good time to slow down, but that's just me.

You warm climate guys just wouldn't understand. 2800 miles through snow and ice, dang right I'm going to make some time when I can. Stay home if you're scared.

 

[raychem]

I have done this conversion and have posted my results on this post:



https://www.turbodieselregister.com...-swapping-3-73-3-42-gears-14.html#post1854360.



My responses are post #'s 183 and 209.



Look cost will vary be region or shop but for a 4x4 ... 1200-1400 for front and rear ring and pinion sets along with front carrier which has to be replaced. Now install could run up to 1000. 00 depending on the shop. It is not hard work but it is not a walk in the park either so there you have it.





Richard

 

[BHolm]

I have done this conversion and have posted my results on this post:



https://www.turbodieselregister.com...-swapping-3-73-3-42-gears-14.html#post1854360.



My responses are post #'s 183 and 209.



Look cost will vary be region or shop but for a 4x4 ... 1200-1400 for front and rear ring and pinion sets along with front carrier which has to be replaced. Now install could run up to 1000. 00 depending on the shop. It is not hard work but it is not a walk in the park either so there you have it.





Richard

I thought I read on the R&P vendors website that a spacer can be used in the front diff so you do not have to replace the carrier. Anybody confirm?

 

[JimKing]

I'm wondering what it cost to convert your 4x4; I can give you the cost to go the other way. 3. 42 to 3. 73. A1 Differential in Phoenix did the job using Richmond gears for $975 in 2003.

 

[ronman]

I can't think of too many situations where one would need both at the same time. If you are in a situation where you are cruising at a higher speed and want to utilize the higher gearing of the overdrive, odds are you are not going to need 4x4. Conversely, if you are wheeling' or in conditions (i. e. snow) where you need 4x4, odds are you don't need the additional gearing of the overdrive.



The GV unit hooks up to the ecm and will disengage when in 4x4 as protection for the overdrive.

I am in the same camp as BrianJ. OTOH, I also have an AWD Bimmer too if I don't need the truck and want high speed AWD.

I can think of several recent occassions where I would have liked both, that is why I brought it up. I76 to Neb and I80 all the way across around Christmas comes to mind. Straight roads, icy sections, need to make some time, like the added stability of 4x4. Keep in mind that even at 60-65 with the early G56 ratios, you are turning some rpms, more than I would like anyway.

BHolm, I guess your only option would be the 3. 42 gears. They are a bit cheaper ($2400 -ish) than a GV OD ($3K -ish) but only reduce your rev's by 200 or so where GV reduces by 500 or so. If the bulk of your high speed driving is not in slippery weather, then maybe GV still makes sense? FWIW, I just saw a used one on ebay, $1K current bid. I'm sure GV will sell you everything you need to fit it up to your truck. That's what they did for me since mine was kitted for a 1Gen CTD.



I just took my truck on a 150 mile highway trip this morning and can say I LOVE the OD on the highway! 1750 RPM's at 70MPH. I also just uploaded Smarty Jr and the truck feels superb! Overhead MPG's were clearly up 3 - 4 too.

 

[raychem]

BHolm, I guess your only option would be the 3. 42 gears. They are a bit cheaper ($2400 -ish) than a GV OD ($3K -ish) but only reduce your rev's by 200 or so where GV reduces by 500 or so. If the bulk of your high speed driving is not in slippery weather, then maybe GV still makes sense? FWIW, I just saw a used one on ebay, $1K current bid. I'm sure GV will sell you everything you need to fit it up to your truck. That's what they did for me since mine was kitted for a 1Gen CTD.

My rpms are down 325-350 and I am a auto truck. As for the front carrier, I ALWAYS replace it on a 4x4, I do not like the idea of a spacer. On tires. . ok I guess but if you have a problem with it on a diff... . watch out! I do not want to post specific prices but I did quote round about figures.



Richard

 

[BSMcCauley]

I can think of several recent occassions where I would have liked both, that is why I brought it up. I76 to Neb and I80 all the way across around Christmas comes to mind. Straight roads, icy sections, need to make some time, like the added stability of 4x4. Keep in mind that even at 60-65 with the early G56 ratios, you are turning some rpms, more than I would like anyway.

If you want an aftermarket OD that will allow you to choose to also use 4WD or not, go with the Overdrive by GearVendors. It goes between the transmission and transfer case and shifts exactly the same as a 2-speed axle, for those familiar with bigger trucks. That's the route I'll be going when I finally convince my partner in life that there are alternatives to listening to the engine race along unloaded at the 80 mph speed limit across West Texas I-10.

 

[ronman]

If you want an aftermarket OD that will allow you to choose to also use 4WD or not, go with the Overdrive by GearVendors. It goes between the transmission and transfer case and shifts exactly the same as a 2-speed axle, for those familiar with bigger trucks. That's the route I'll be going when I finally convince my partner in life that there are alternatives to listening to the engine race along unloaded at the 80 mph speed limit across West Texas I-10.

I don't think this is true... Gearvendor's mounts after the transfer case. I believe US Gear's OD goes between the trans and transfer case, but, my understanding is that US Gear does not offer adaptors for the 3Gens, and has no plans to offer them, but I could be wrong about that.

 

[BSMcCauley]

I don't think this is true... Gearvendor's mounts after the transfer case. I believe US Gear's OD goes between the trans and transfer case, but, my understanding is that US Gear does not offer adaptors for the 3Gens, and has no plans to offer them, but I could be wrong about that.

While it is true that the US Gear OD will allow the use of 4WD, I have only looked into that option in so far as relating to my 96 truck. Therefore Ronman is probably correct regarding no 3rd gen application for this option.

 

[klenger]

You warm climate guys just wouldn't understand. 2800 miles through snow and ice, dang right I'm going to make some time when I can. Stay home if you're scared.

I spent my first 25 years in Michigan and the next 27 years in Colorado. I think I know what driving on snow and ice is like.

 

[AH64ID]

You warm climate guys just wouldn't understand. 2800 miles through snow and ice, dang right I'm going to make some time when I can. Stay home if you're scared.

Sorry... I am a cold weather guy and that speed in 4wd gains you nothing... . I cant think of a real time when you would need the GV and 4wd...



Here is a rpm chart on 3. 73 vs 3. 42



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3. 42's are a 8. 3% reduction, the GV is a 22% reduction.







This is what tires will do for you



If you have 3. 73s and 265/70/17 stock this is what tires does to your effective ratio. . using OEM and toyo rev/mile specs... each tire is a little different, but you get the idea.



285/70/17 : 3. 605

285/75/17 : 3. 481

325/70/17 : 3. 378

 

[betterthanstock]

Nobody answered the original question. I hear talk about what the RPM gets to; nobody answered what it costs to do the conversion. RHestand seems happy with putting on larger tires and a leveling kit. Motorhead doesn't have the same transmission; and assumes that I can't calculate. Others talk about an overdrive unit -- I wasn't asking about external solutions such as that. I think that the '07 & up overdrive ratio with the 3. 42's would be perfect for those of us that do not tow regularly, and do not tow heavy.

So, once again, I ask, has anybody done this conversion, and would you do it again to resolve the RPM issue? I have larger tires on order.

I have converted from 4. 10 to 3. 73 with an NV5600, which is nearly identical to your G56 w/3. 73 going to 3. 42.

I also put bigger tires, so I went from 2300 rpm @ 70, and 2630 rpm @ 80,

to 1920 @ 70, and 2200 @ 80. Definately worth it. See my previous post for cost. Worth twice that much.

 

[sweeda]

I had my rear end gears replaced in my 2 wheel drive in 2005. parts cost and installation by a shop that only works on diffs. Out the door with taxes $730. 00. On a 4 wheel I wouldn't know. Even if it is twice as much for the front it would still be only about half the cost of an OD unit. I'd say gear change is the way to go cost wise. Find a good shop to do the work because a broken gear at 70 mph will not be pretty.

 

[PGarrett]

Has anyone checked in to replacing the overdrive gear only in the nv5600 or g56 with say a 0. 625 overdrive gear. I dont have a clue but I can only assume this would be cheaper. Yes the trans would have to come out to replace the overdrive gear if there is a gear made that would fit our trans.