3.73's v 4.10's

[PFranzese]

The manual six speed/3. 73 combo is okay for driving and towing because gearing in the G-56 is a bit lower than in the previous NV-5600 transmissions. It is the only choice so it has to be acceptable.

I have an 09 2500 with 4. 10s and a G56. RPM's are high on the highway, ~2100 at 65, but I don't drive much on the highway without a trailer. Tows great in the hills of west virginia with a car trailer and a heavily modified Jeep in tow, the E-Brake and 4. 10s really pulled the hills and saved my brakes on the way down. I didn't really want the 4. 10s but I got a great deal on the truck and the other 99% of it was exactly what I wanted.

 

[HBarlow]

I see I was wrong about the gearing choices. '09s now offer 3. 42, 3. 73, or 4. 10 gears with the G-56 manual transmission. Previous years, '07 and '08s, offered only 3. 73 gears with the G-56 manual.

 

[DMcGalliard]

I have an 05 six speed with 3. 73. My fifth wheel is 15k. The problem that I have is get the power band with the edge I am traveling in excess of 75mph and for a long hill I will get up to 80. The truck has the power but 80 is too fast. 4. 1 is probably better for towing over 13k. Not sure how much the 3. 73 improve the mileage over the 4. 1, sometimes I get 22mpg on flat ground. Knowing what I know now I would go with the 4. 1.
Dave Mc

 

[macdaddy]

I have an 05 six speed with 3. 73. My fifth wheel is 15k. The problem that I have is get the power band with the edge I am traveling in excess of 75mph and for a long hill I will get up to 80. The truck has the power but 80 is too fast. 4. 1 is probably better for towing over 13k. Not sure how much the 3. 73 improve the mileage over the 4. 1, sometimes I get 22mpg on flat ground. Knowing what I know now I would go with the 4. 1.

Dave Mc

This was the reason I ordered the 4. 1:1. Towing all day in 6th 2K RPM equals 62ish MPH. I love it.



Down side is when empty for long hauls. I usually limit the the speed to 75 mph. The fuel economy is decent and the motor isnt over reving



Mac

 

[Matt400]

So to answer the question we should know-

* what size tire you will be using

* what speed you would like to cruise at



We already know what RPM the engine likes and the transmission gear ratio so with the other two figures you can make a selection on the axle ratio.

 

[HBarlow]

I agree with DMGalliard and macdaddy. I ordered my first Dodge Ram, an '01 HO/six speed with 3. 54 gears, for towing an 8,500# Airstream travel trailer. It was perfect for that combined weight.

Later, when I bought a 14,500# used Travel Supreme fifth wheel it was nowhere near perfect. Sure, the Cummins still had the torque to start the load and the power to tow but the gearing was wrong for that weight. It grunted to get the load rolling in first gear and required more downshifts for hills. The truck just wasn't geared comfortably for those weights.

Since then I've ordered 4. 10 gears.

 

[Carlacee]

As soon as I get a chance I'll scan the page in my manual that states 6th gear is not recommended for towing and post it.



I'm glad to hear that you folks with the NV5600 are pulling in 6th gear without any transmission problems. Ill try to find the thread where the NV5600 was loosing 6th gear and post the link.



Just as soon as I know my trailer weight will be I'll post as well.

 

[Slow Six]

I lost 6th gear on my NV 5600 about 6 weeks ago. I have towed fairly heavy and at highway speed. At about 155,000 miles pieces broke off the sixth gears. I have removed the "chip" and returned to stock power and will be using Mopar transmission oil from now on. I cannot prove it but I feel the failure was due to to much power and lack of performance from the oil I was using. I also had a rear diff failure using the same brand of oil. I am running the 3:73 gears which were great with the added power but in stock form the 4:10 would be better. I've tried towing in 5th. but the RPM are uncomfortably high and mileage really drops. I also accept the fact that I was my own warranty station, I played, I paid. Even in the big rigs power increases often lead to failure down the drive train.

 

[steved]

I have read of now only two sixth gear failures.



The first was a hot shotter towing well beyond the recommended GVW (I think I remember 26k was his normal, and that trans lasted something like 200k).



And this one is from increased power and towing heavy.



From what I see, in stock form and towing within the recommended GVW, there isn't a glaring problem. And there are lots towing hard in 6th that never have trouble... these few we read about don't even make up the percentage of bad parts produced, let alone the failures from extremely hard use (or abuse).



If we saw the loss of 6th the way the NV4500 loses 5th, then I would say your argument has some merit.

 

[Slow Six]

I probably overused 5th gear on my NV 4500 way more than 6th in my NV5600 and never had a problem. I sold the truck to a young guy who loved the power (and uses it) and so far he has not had a problem neither. That engine was turned up as well. You are right though, there are less problems with the NV 5600 and I like the gearing a lot more. If I could do it right now I would get a new truck with an automatic and gearing for the maximum weight rating as we plan to upgrade our fiver in the future.

 

[HBarlow]

The NV-5600 in my '01 HO/six speed lasted 302,000 miles before the big center bearing got rough and noisy. I used nothing but Pennzoil Synchromesh Lube and seldom changed it. I think neglect contributed to the failure because it had a slight leak from the shifter base that allowed the lube level to get a little low. Sixth gear showed wear when Standard Transmission tore it down but it was not sixth gear that failed, only the center bearing. I reject the claims that sixth gear was weak in the NV-5600. I only have experience with one but it was a very durable transmission.

Against all TDR advice I towed 99% of the time in sixth gear with 3. 54 gears. If the mighty Cummins could hold 1600 rpm or above at full throttle up a long steep grade I let it pull. I never downshifted if the engine could hold 1600 (peak torque) rpm . It had 275 hp Bosch RV injectors and ran strong but no other modifications.

I am still a big fan of the NV-5600 and would have ordered the '06 with manual six speed if the NV-5600 had been offered. I didn't want a dual mass flywheel/clutch or the G-56 so ordered the 48RE then had to spend a small fortune having a DTT rebuild.

Cee, please hurry with that sixth gear warning in your owner's manual.

 

[CUMMINZ]

HB,



I know nothing about manual trannys. Your comment about running in 6th. gear pulling x-hard at 1600rpms... .



Since I installed the egt guage in the manifold and have watched it intently, I have learned a lot. When my 6. 7L starts pulling hard in 6th. (68rfe) it builds egts very fast and can go to high if I don't down shift. Just by down shifting and raising the rpms my egts go down quickly.



I'm afraid that few folks think that pulling hard in tall gears to keep rpms down gives you better mileage.



This was off subject.

 

[NIsaacs]

I think the NV-5600 transmission is maybe the best pick-up transmission made. However as in "all" manual trannys with overdrive, overdrive is the weak link. Over time they will fail, usually before any other part. The bigger and better just take longer.



Keep in mind that overdrive includes almost every part of a manual transmission. The power comes in with the input shaft, drive gear and bearing. The drive gear turns the drivin gear on the counter shaft, the drive gear on the counter shaft drives the overdrive gear on the output/main shaft. All the gears, shafts, bearings and case recieve torque stress and heat.



Thats why the little 4sp transmission that was around for ever lasted so long. It was direct drive. Direct puts almost no stress/heat on any part of a manual transmission.



The big trucks and even medium dutys are all going back to direct drive trannys with high rear axle gears.





"NICK"

 

[HBarlow]

HB,

I know nothing about manual trannys. Your comment about running in 6th. gear pulling x-hard at 1600rpms... .

Since I installed the egt guage in the manifold and have watched it intently, I have learned a lot. When my 6. 7L starts pulling hard in 6th. (68rfe) it builds egts very fast and can go to high if I don't down shift. Just by down shifting and raising the rpms my egts go down quickly.

I'm afraid that few folks think that pulling hard in tall gears to keep rpms down gives you better mileage.

This was off subject.

You are correct. Keeping your foot in one with a manual transmission in sixth gear on a grade, loaded, does produce some heat but the factory stock engine is not hurt by extended running at 1425* or even 1450*.

My '01 HO/six speed with 275 hp injectors would quickly peg the pyro gauge at 1600* if I didn't watch it. I let it pull for 325,000 miles at 1300* to 1325*. The only trouble I ever had was a seeping head gasket at the front of the engine at around 225k miles. I think that was caused by poor quality head gasket, not heat.

The reason I did that was, in part, stubborness, but I was backed up by the Cummins Operation and Maintenance Manual ISB Engine" which I ordered from Cummins soon after I bought the truck. I have quoted the manual here in TDR several times in years past but basically it advises drivers to let it pull at full throttle down to peak torque rpm before shifting. I sent an e-mail to Cummins years ago quoting the guidance contained in their book and asked them if the advice applied to my Dodge Ram. Their reply was to chuckle at my quoting their manual to them and they assured me it was the proper way to run it. I did and have never regretted it.

A good friend who knows trucks told me that the power pulses of the Cummins put added stress on the sixth gear at lower rpm. I believed him but other than some wear visible at tear down don't think it hurt anything.

TDR lore is not always correct.

 

[BLNRAY]

i have 4. 10s and a 6 spd cant tell you how many times i have tried for 7th gear. i am thinkin of regearing maybe 3. 42. dont think my towing will be affected that much

 

[HBarlow]

I had to take a quick break for soup and sandwich so didn't finish the reply above.

I'm not sure what you meant in the comment about better mileage. I didn't let the engine pull in sixth gear for fuel mileage if that's what you meant. Actually, I'm the last guy on TDR to worry about fuel mileage. I have never checked and recorded it on any of the three Cummins-powered Dodges I've owned. It is what it is and I can't change it. I have no idea what fuel mileage my current truck gets. I pay no attention to it. I simply stop and buy fuel when my Transfer Flow tank pump begins hammering on an empty auxilliary tank.

For calendar years 2005, 2006, and 2007 I paid Flying J about $27,000 each year for fuel. What good would saving a mile per gallon have done me?

When I owned a manual six speed I let it pull in sixth gear at peak torque because that's what an inline six cylinder diesel engine is designed to do. The engines produce massive torque at low engine speeds. Engines wear slower with lower crankshaft speeds. In theory they run more economically at lower engine speeds also.

Big trucks run at even lower engine rpms. The big truck industry spends fortunes designing the trucks, engines, transmissions, and training drivers to shift up early and shift down later to keep engine speeds low for increased fuel economy and reduced wear. Why buzz the engine when you have an engine that will pull steep grades in top gear?

If I wanted a high rpm screamer I'd buy a Furd that has to be revved to pull a hill.

 

[Carlacee]

Retraction

Cee, please hurry with that sixth gear warning in your owner's manual.

Harvey:



I couldn't find it so I've retracted the statement (see my post). I'll keep looking though, I know a read it... . =(



My apologies to all,



Cee

 

[HBarlow]

Cee,

No apologies necessary. You didn't offend anyone.

We all get corrected occasionally when someone else points out something we believd was true simply wasn't.

I think you'll find that was something someone told you or perhaps something you read about another truck and mistakenly attributed to the NV-5600 in the Dodge Rams.

Anyway, the point is you can tow in sixth gear as long as you keep the engine rpm at or above 1600. It won't hurt a thing.

 

[mvaughn]

I loved my 2001 with the NV5600 and 4:10's and I now love my 09 with the 68RFE and 4:10's. The 09 is a quiet, strong pulling truck and feels smooth at about 1750RPM and 63MPH. I like a little room between peak torque and the RPM I cruise at.