prlsnpsdodge

AFternoon. Just doing some research here, and I am wondering about the best solution for a little better mileage out my truck. For what it's used for, I am down to 2 options.
1st- changing out the rear gears to a lower (numerically) ratio. I can get 3.53's or even 3.42's put in for about $11- 1200.
2nd- I could add the Gear Vendors Over/Under drive unit and gain an extra 22% in 6th. But that option costs about $3300 after parts and install.

Any Experience/ Advice/ Warning ya'll might have would be a great help!

Load Hauler 04

Gear Vendors work very well in 2wd trucks because the unit mount behind the trans. From what I have been told from friends of mine, they handle heavy loads without any problems. The problem with changing your rear gears is your stuck with a higher gear all the time, with a two speed you have high and low at the flip of a button......

haulin-rv

Search and read more about a gear vendor, with things like a 5000 mile service interval I'll pass. And with the cost the truck would be worn out before you would recoup it.

mitternocht

The GV adds 28.6% OD.

I just took my GV off last week, after switching to the 3.42s and the newer g56. I know people think I’m crazy, but my trans was starting to grind when catching 5th so I figured I’d swap to the newer unit with higher gears. The GV was too much OD with the 3.42s unless I wanted to do 90 all the time, lol

If you are getting 18 city/20.5 hwy than you are getting what I got with the GV, maybe better, but you have 2 wheel drive, mine is a 4x4.

Maintenance not that bad w/ GV, just pull plug, drain, refill, takes ~a qt, 10 min you are done. You are supposed to pull the pan and clean some screen at some point, but I haven’t done that. Maybe I’ll do it now that it is off, lol.

haulin-rv, which g56 do you have? I think they put a few of the newer ratio’ed trans behind the 5.9 in ’07??

etn550

I would re-gear the rear end. In fact I intend on doing that with my '06. Go to 3.42.

I had a GV unit on a '96 12 valve. Bought the truck with 123k on it and sold it with 175k. the GV was on it early on and the PO towed a 5th wheel full time camping.

Everyone told me the GV would only last 70 - 80 k and i proved them wrong but it did fail. They do not have the kind of life one would expect from a major powertrain component. Mine was on a 5 speed and it made a perfect 7 gears with 4.10 rears.

On your truck or mine for that matter it will be too tall to tow effectivly, so will only be for unloaded. (I'm assuming you have 3.73 gears now)

If you re-gear all gears will be a little taller (10% if going from 3.73 to 3.42) and this means still enough in 1st to pull a load and 2nd will be better starting empty as you can go a little farther before hitting 3rd.

Some Quirks about GV:

1. It makes it's own oil pressure to shift so it will not work below 23 mph. If you are in OD and drop too low a speed it will suddenly and drastically slam drop to direct. You will cringe and look in your mirror for oil and parts on the road.

2. It uses a cone clutch and a big sprag one way clutch in OD. Think of the sprag as a one way ratchet without teeth. When the engine is pulling hard the sprag is locked and no slip in OD. BUT when you are downshifting or want engine braking the cone clutch will slip. Therefore, you cannot safely use it with an exhaust brake.

3. Rules #1 and #2 make it a hassle.

4. It holds a small quantity of oil and must be changed frequently. Mine called for 50wt gear oil. Now they may use something different but it will be another fluid to deal with regularly. The cone clutch will make the oil dirty.

5. They used to exchange a burnt up one for $750.00 so that is one way to get one in new condition cheaper than new. Buy used and exchange.

6. It is 22% jump. Too much really to be useful with a close ratio 6 speed.

7. Seems like the only auxillary trans option left but I am not going down that road again and the 6 speed is a bad match for it.

Mine is 4x4 so my costs to re-gear are double yours yet I'm not going to consider GV.

JMHO, Others may have different ideas.

etn550

.78 ratio which is 22% Still too much to match the 6 speed. 12 - 15% would be perfect for gear splitting the G56.

Colo~Dirtbikers

Too bad we couldnt put on a brownie box from old semis. They were 2 speed and right about 20%. Those lil dudes would outlast the truck.

prlsnpsdodge

Thanks for all the input! Cost wise - it is much cheaper just to go down to 3.42's vs. the current 3.73's. To be completely honest, I wanted this cummins motor for it's longevity and mileage. The haulin' power was pure bonus as I only haul every now and then. it is hard for me to rationalize $3500 just for a few more MPG's (and basically only 1 more gear). I appreciate all of the info!!

mitternocht

The numbers are all about semantics.

The GV will increase your speed by 28.6% when you return to the RPM when engaged.

True in 5th over you get an effective ratio of ~.78, (22% change) however that makes you go just over 28% faster, not 22% faster.

If you drop ratios by 50%, you go 100% faster!


1/.7776 = 128.6 so at 1000 RPM input to GV you are seeing 1286 RPM out of the GV.

The GV ratio is too high for splitting gears on the 6th speed.

Jim O

I know a guy that has a 75 chev crew cab with a 4-71 N series with a turbo and aftercooler and he has it hooked to a 4 speed Allison and a 3sp brownie that he says it from a 1950-53 Chev or GMC 2 ton. and I have seen the brownie apart and you are right it is bullet proof. Someone else said that you can't use a gearvendors with an exhaust brake this is wrong. They do require that you electricly lock out the ex brake when in OD but why would you want exhaust brake in OD when you get more hold back in direct. As for the downshift that he mentioned you do get used to the way they work and I can't say that I have had the unexpected downshift in a couple of years. I do agree the sump should be larger and I have made a larger one for my unit. It now holds 80 fluid oz. or twice as much as stock. Some one else said the splits are not right for a 6 speed, I will agree they are not perfect but they are better for a NV 5600 than the later standard trans. I can't visualize backing a heavy trailer up a hill with 3:42s and the high reverse gear that is in the G5600. Also the originator of this thread did not say what trans he had but regardless with the gear vendors you can spit the gears and sometimes half a gear is all you need to make the hill.

Mexstan

You have overlooked an easier and much cheaper third option - taller tires. I considered a GV years ago but could not see any decent return on it, so went to my present 315 tires. Huge difference compared to stock tires and I am happy, even when towing.