AAM gear question

[RHuot]

I have an question regarding the AAM gearing for the 11. 50 axle provided on the 2007 Dodge Ram. I have just recived information from AAM (American Axle & Manufacturing) which provides three gear ratios for the Dodge 11. 50 axle 3:42, 3:73 and 4:10. I am familar with the 3:73 and 4:10 but in what application is the 3:42 used? Could this be used with the 6. 7L six speed manual?? Just thinking out of the box on this, looking for commments and the best possible fuel milage.



Snow Pro

 

[mberry]

I wish they would have provided the 3. 42 option when I bought mine. That's what it would have now if it were available then.

 

[RHuot]

Snow Pro

I have not seen any indication the 3:42 is offered from the dealer, maybe it is for the SRT. I will be enquiring now. If AAM can provide the 3:42 in a 11. 50 why can't it be specified in a new order? Any thoughts?

 

[betterthanstock]

I have not seen any indication the 3:42 is offered from the dealer, maybe it is for the SRT. I will be enquiring now. If AAM can provide the 3:42 in a 11. 50 why can't it be specified in a new order? Any thoughts?

Matching front 9. 25" needed for 4x4

 

[RHuot]

Snow Pro

Are you indicating for a 3500 the rear axle is 11. 50 and the front would be 9. 50?

 

[SuperSteeler]

Are you indicating for a 3500 the rear axle is 11. 50 and the front would be 9. 50?

9. 25 for the front on 2500/3500 4wd.

 

[TowPro]

Using Klengers chart I notice My truck with the 2006 G56 and 3:73's would improve by 6mpg at 2000 rpm in 6th gear by changing to 3:42's, or around 100rpm lower in 6th gear. Wonder if that is enough to make it worth it?



Now if I could get 3:08's I would be interested. That adds 13mph at 2000 rpm, or lowers my 65mph to 1650 rpm. I think that would save fuel.



but my caculation don't help the 07 owners since I think they come with a different OD ratio on the G65?

 

[RHuot]

Now were getting somewhere. . These engines make all this torque, are we getting the most out of it?



I just confirmed that 3:42 is avalible for 2007 in both the 11:50 and the 9:25 AAM axles for the 4x4 application. I now have a question into Dodge regarding the avaiblity to the customer.

The question to all TDR members... Could the 3:42 be a viable solution???

 

[klenger]

Using Klengers chart I notice My truck with the 2006 G56 and 3:73's would improve by 6mpg at 2000 rpm in 6th gear by changing to 3:42's, or around 100rpm lower in 6th gear. Wonder if that is enough to make it worth it?



Now if I could get 3:08's I would be interested. That adds 13mph at 2000 rpm, or lowers my 65mph to 1650 rpm. I think that would save fuel.



but my caculation don't help the 07 owners since I think they come with a different OD ratio on the G65?

CAUTION: My worksheet makes no claim what-so-ever as to MPG differeneces, only RPM vs. vehicle speed. There is not a linear relationship between RPMs and MPG.

 

[RHuot]

Snow Pro

Yes, but how about RPM/Torque/fuel requirements? Torque is the real factor here correct?? The Cummins engine torque peaks at around 16 to 1700 rpm and continues to fall off with the higher RPM. The higher RPM will reduce the fuel milage (flat surface travelling). So my goal would be to keep the engine RPM (with gearing) within the engine torque spec, limiting my throttle requirement to maintain a max 75mph vehicle speed. Hill climbing would require a down shift to keep the RMP within a 500 RMP split. I think we can all agree that over 2,000 RPM is wasting fuel. I believe the Diesel has a completely different torque band than a gasoline engine. Therefore keeping the engine within the torque band provides more torque with less pedal. At this point my only consern would be potential EGT's, but less fuel pedal should minimize the turbo use and the engine should breath as designed.



Just my thoughts

 

[TowPro]

I agree RHuot, I feel the 3:08's would make my 1st gear a little more usable and I feel going 1650 RPM at 65 (instead of 2000) would some fuel. I don't mind downshifting if I have to climb a hill.

In addition, wind load is a factor we cannot measure into this very easy. I know if I cruse the back roads at 45 I can see 23 on the overhead, but at 65 I see 17 on the overhead, how much of this difference is because of wind load VRS RPM?

I know the overhead is not perfect, but I figure it is the same amount of inaccuracy at 45 as it is at 65 so 6 mph means something.

 

[Ereynolds72]

Now were getting somewhere. . These engines make all this torque, are we getting the most out of it?



I just confirmed that 3:42 is avalible for 2007 in both the 11:50 and the 9:25 AAM axles for the 4x4 application. I now have a question into Dodge regarding the avaiblity to the customer.

The question to all TDR members... Could the 3:42 be a viable solution???

Hopefully I'll be truck shopping soon so I'd be all over this. Has anyone found out any more on the availability of 3. 42 gears? I want the G56 but the high gearing has been a concern to me. I eventually want to run 35s and this seems to be the ticket.

 

[PGarrett]

Will the 3. 42 gears be avaliable in the parts department? I want to find out what it will cost to convert my 04. 5 from 3. 73 to 3. 42 gears

 

[jcarey]

3. 42's sure would be great for those who don't haul heavy.

 

[y-knot]

Sure both the 3. 42 and the 3. 08 would be great for those that only use there trucks to commute back and forth to work... ... But beings that the Dodge Ram Cummins combo is designed for those how use there trucks to tow or haul heavy loads, these gear ratios would make a dog out of the truck and relay lower it's load handling capacity. So you see why Dodge does not offer the 3. 08 and has so far not offered the 3. 42. I would think the 3. 42 was offered up on the '07 models in response to the high fuel cost. If you do buy yourself a truck with the 3. 42 ratio, then please won't post latter complaining how your truck has no guts when loaded or towing. Also, if you plan on lifting your truck and running larger tires, I would not select the 3. 42 ratio, as it's just to low to be practical.

For you that want to change to a lower ratio, I have had two other trucks that I had new and lower gears installed, both cost about the same. One was a Chevy with the IFS front axle that was roughly $250 more, but you can figure roughly $600 per axle + parts.

 

[LesStallings]

Like y-knot said, the heavy duty Ram is intended for heavy duty use. Those of us that tow need every bit of the 3:73s or 4:10 for the really serious guys. When I'm pulling over 15K pounds I really, really want 2,000 RPM or a little more.



So, if you don't use your truck as intended and want to lower your cruising RPM, bigger diameter wheel/tires is the easy way to do it. The guys with the really big tires are wishing for something better than the 4:10 to get the gear multiplication back that they lost with the big tires.



Some people choose a diesel because it's cool. Other choose a diesel because it can pull heavy loads. Dodge currently only addresses those that buy a 2500/3500 for its rated capacity. Maybe Dodge should offer a hot rod diesel option, optioned for performance and not towing. I bet they would sell a bunch. It would probably have a 12 month, 12,000 mile warrantee and the service department on the lookout for any sign of mods.

 

[MSLiechty]

Just returning from a 2300 mile trip I came up with these conclusions. 2100 RPM is the threshold of pain. anything near this and above the MPG were dropping off quite quickly. Since I don't do a lot of heavy towing I'd be real happy 3. 55, but if the 3. 42 is available for 2007 why couldn't gear sets be obtained for the older trucks with 3. 73 and 4. 10 gears.



Michael

 

[cerberusiam]

Yes, but how about RPM/Torque/fuel requirements? Torque is the real factor here correct?? The Cummins engine torque peaks at around 16 to 1700 rpm and continues to fall off with the higher RPM.

Those are 12V numbers not the CR engines. TQ curve and fueling is completely different on CR engines. Put one on a dyno and under a load and you will find 1600 to 1700 worthless unless empty with a tail wind. This is assuming stock tune, fueling mods completely change things.



The 3. 42 would be great with a 9 speed transmission and 7 gears at 1:1 and less, otherwise, to hard on the rest of the drive train components for the rated weight. There is a reason medium duty trucks have tall tires and low gears.

 

[RHuot]

Snow Pro

I attempted to contact someone in engineering at Dodge regarding the AAM 3:42 gearing option but the responce had no direction and was not helpful. Maybe some of you can help with a connection at Dodge?? I find that most saleman will not take the time to fully investigate this. For some of us this truck is a long term investment. For the Cummins engine gearing options are critical to the specifications. Personally I am not intersted in stump pulling or the big 4X4, been there done that. I am looking to maximize my fuel milage and pull a travel trailer once and a while. If I have to down shift on a hill so be it, I'm just sitting there anyway.

 

[klenger]

If Dodge offered the CTD with 3. 42's, a whole bunch of people would order them that way and STILL tow 15,000 lbs, and Dodge would have a lot of serious warranty problems.