My journey to 40mpg with a 1ton diesel.

[Stoked]

Originally Posted by mikeyjd

Yeah my gearing is really short (I can shift into 5th at 30mph without lugging the engine) how hard is it to track down the 3.08 gearing setup?

I didn't see this covered...Some Dodge trucks (and maybe some others) came with 3.08's from the factory. Look for a Dana 61 axle. Similar to a Dana 60, but had an offset pinion to account for the large pinion gear of the 3.08 set. Make sure the gear set in it is good, though, because new ones are almost non-existant. Bearings and seals are all still available as they are the same for a 60.

[JQmile]

Congrats on breaking 30mpg! You have electric fans yet?

[mikeyjd]

Originally Posted by JQmile

Congrats on breaking 30mpg! You have electric fans yet?

I didn't install any e-fan yet. It's on the list of things to do eventually.

[crashnzuk]

Originally Posted by Stoked

I didn't see this covered...Some Dodge trucks (and maybe some others) came with 3.08's from the factory. Look for a Dana 61 axle. Similar to a Dana 60, but had an offset pinion to account for the large pinion gear of the 3.08 set. Make sure the gear set in it is good, though, because new ones are almost non-existant. Bearings and seals are all still available as they are the same for a 60.

Correct, a 3.07 gear was standard on the early non-overdrive automatic cummins powered trucks. You want to find a complete axle from an 89 thru mid 91 non intercooled automatic truck.

If you are still trying to figure out how your wiper arms come off, just lift them up like you're cleaning the window and flip the little tab outward from the shaft and let the wiper down onto it to hold it out. You will now be able to jiggle and lift it straight off of the spline, very easy and no tools required.

Travis..

[crashnzuk]

I also had some thoughts about your transmission. As I am sure you've heard, the Getrag 360 has a spotty reputation. Two of the things that I have heard will kill them rapidly is flat towing and lugging. Engine off coasting is basically flat towing without the tow rig. The problem is that the cluster gears aren't turning with the engine off, so oil doesn't get pulled up high in the trans with only the output turning. This will kill the main shaft. These engines use so little fuel at idle, I personally think engine on coasting would be almost as good for economy and much better for the trans.

The other thing is lugging. The consensus amoung Cummins guys is that anything below about 1700 behind a Cummins is very hard on the internals (of any transmission). The guys with manuals behind V8 diesels don't seem to have this problem nearly as bad. I think the problem is the harmonic vibes of the inline 6 being more harsh than that of a smoother running V8.

On your turbo, your exhaust housing is fairly large (2nd largest housing installed on a Dodge). If you swapped to a smaller hot side housing it would make your engine a lot less laggy, but you would need to make adjustments to your AFC (provides boost referenced fueling) to keep from being into the additional fuel more than you are now.
Travis..

Travis..

[slowmover]

The consensus amoung Cummins guys is that anything below about 1700 behind a Cummins is very hard on the internals (of any transmission).

I wouldn't be too sure of this [consensus] if we are speaking of a quarter century of Cummins/Dodge pickups. It may be more year/model/trans specific. If so, which?

[crashnzuk]

I'm most familiar with 5 speeds since I haven't yet owned a 6 speed truck. Having been around a number of forums since buying my truck 10 years ago, I have read and heard numerous stories of guys destroying their 5 speeds by running too low an rpm. Either guys short shifting and running around at low rpm, to guys running an aux overdrive on the interstate. The Getrag has a bad reputation due to many being incorrectly set-up from the manufacturer, but they also crap counter shaft bearings as a common failure. The getrag should also be overfilled by about a quart to keep the front bearing happy as well. The NV4500s have 5th gear problems. No matter what manual you run, they are all VERY expensive to repair. I choose to keep my trans as happy as possible by keeping the rpm up rather than lug it. My original getrag has over 185k on it so I feel whatever I'm doing must be ok.
Travis..

[bandit86]

I just bought a 2003 dodge cummins 4x4 crew cab 6 speed. With the scan gauge showing tps at 17 I got 10.9l/100 average on big hills with a 12 ft boat hanging out the back and the back seat loaded with gear. Once the road leveled off I got down to 9.5, that's with a 80km speed limit and doing roughly 95 for 8 hours. The truck also has a bullydog program on the lowest setting. Haven't had a chance to try long distance driving since.

[bandit86]

Originally Posted by crashnzuk

I'm most familiar with 5 speeds since I haven't yet owned a 6 speed truck. Having been around a number of forums since buying my truck 10 years ago, I have read and heard numerous stories of guys destroying their 5 speeds by running too low an rpm. Either guys short shifting and running around at low rpm, to guys running an aux overdrive on the interstate. The Getrag has a bad reputation due to many being incorrectly set-up from the manufacturer, but they also crap counter shaft bearings as a common failure. The getrag should also be overfilled by about a quart to keep the front bearing happy as well. The NV4500s have 5th gear problems. No matter what manual you run, they are all VERY expensive to repair. I choose to keep my trans as happy as possible by keeping the rpm up rather than lug it. My original getrag has over 185k on it so I feel whatever I'm doing must be ok.
Travis..

The transmission relies on splash lubrication, at low rpm there might not be enough spray. The other thing is Lucas oil stabilizer, it makes the oil cling and less likely to splash, also because the gears pick up oil and hold onto it (try the little display unit they have) and because all the oil is on the gears there is nothing on the bottom to pick up

[slowmover]

The Getrag and NV=4500 haven't been used on CTD's for about twenty and fifteen years respectively. Thus the question as there have been a couple of transmissions since then. I run the highway at 1,725-rpm on an NV-5600.