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Hersbird 02-13-2017 11:00 PM

New to me 2004 Cummins Ram

So I finally found a good deal on a generation 3 CTD Ram 6 speed manual. This is a 2004.5 325hp 4x4, quad cab, long bed SLT. It has 272,000 miles but seems pretty well maintained. A few questions.

1) The tires are less than 50% so was thinking of new ones already. They are stock 265/70/17 31.6" tall. There is a set of new 2016 take off wheels and tires from a 2016 in 275/70/18 that would be a 33.2" tall (for $600!). I think I have 3.73 gears but I can't find any tags and the sticker in the glove box is missing. I think that would drop the rpms by about 100 in 6th but would lift the truck .8 inches. Good, bad, wash? I can hardly buy new LT tires for $600 let alone on wheels ready to run.

2) Mainly this is to tow my camper. The camper also sits very high as it's built deck over tires to allow the whole wall to slide out. The camper is skinned under but does have some plumbing and the jacks and axles hanging down. Would letting the air pass under the truck be better (it's pretty high especially if I add the new tires), or would adding a lower air dam to the front help more?

3) similar lines with #2, the camper is tall and doesn't have much of an aerodynamic nose. I want to haul motorcycles in the bed and have thought about adding a ladder rack over them with an inverted jon boat for use as a boat, but also as an air deflector for the front of the camper. I could get a nice rack and a new boat for around $1000-1500 (much less for an used one). When not camping I could remove it all. I will try and hook up the camper once some snow melts to better visualize what I'm thinking. I could also add coroplast sides to the ladder rack to clean up that air as well and get the nose of the boat to "seal" to the roof of the truck with some cut foam.

4) any advice on when to shift and how low I can safely keep the RPM? It seems to want to keep itself above 750 rpm but would a lower gear be better then to keep to rpms even higher? That would mainly be while unloaded around town, on the highway it will be well over 1000 if not 2000 rpms.

I have read a lot of other advice here from Slowmover, Gumby79, Skyking, oil pan, and others so I am listening to all that advice. I'm going to take the truck in to Gomer's US diesel parts here, they are a great diesel shop, and have them give it an overall inspection and maybe add better fuel filtration if it doesn't have it already, fluids and filter, along with some gauges to start (EGT and low pressure fuel). I'm also considering a remote Fass lift pump with filtration. It does have some blowby but not enough to move the oil fill cap removed and inverted on the valve cover. The clutch feels like it has a lot of pedal effort, I can't imagine that is stock but I need to find somebody with a stock clutch to compare. It has some oil leakage on the front of the pan but not much. I will check in the morning to see if any has even dripped. It's supposed to be 8 degrees tonight and it's outside and plugged in so that will be a good test of a cold start (I need to do a lot of cleaning in the garage to fit this beast in there LOL). Anything to look for or listen for there? Shifting is going to take getting used to, 5th and 6th are kind of hard to find but man takeoffs are easy. Just put it in 2nd a let out the clutch, you don't even need to give it pedal but a little seems to keep it smooth. The overhead MPG says 20.4 and hasn't been reset for 9000 miles so that's promising. It has 7200 hours on it so that averages about 24 mph, not ideal. The only modification looks to be an exhaust brake, air bags, and a turnover ball in the bed (another not ideal sign), the air cleaner, exhaust, intake, suspension seem stock. I'm pretty happy, not perfect but so much less expensive than anything else I have seen, my total cost was $13,000 (with fees and shipping) and that gave my buddy over $500 profit as well.

I'm sure I will come up with 50 other questions as I go.

oil pan 4 02-14-2017 02:02 AM

It appears that taller tires lifting the vehicle up a half inch to 1 inch is enough to over come the aero penalty.
The problem with taller tires is when you go too tall and have too gutless of an engine.
For example my engineer friend bought a ford expedition 2wd with 4.6l engine and auto transmission, the person who had it last put 3 inch taller than stock tires on it.
It had lack luster getup and go and was always well below epa rating even with odometer corrected milage.
After about a year the tires wore out enough to warrant replacement. When he finely put the correct size tire on there it started getting real close to epa fuel economy, it could get out of its own way and could tow half way decent. He said if he would have known the correct size tire was going to do that he would have put the correct tires on when he bought it.

A diesel with a manual transmission and almost unlimited torque won't suffer as bad.

If you are going to be mostly towing with it get the highest load rated tires you can and make sure it has the correct load rated tires on it currently.

Since you have the manual transmission avoid flooring it in 6th gear. The 6th gear is push fitted to the shafts and the engine may put off enough torque to spin the gear, which is really bad.
If you have to floor it to get over a hill just drop down out of top gear.

redpoint5 02-14-2017 02:33 PM

The 2003-2004 Ram/Cummins is my dream truck. Did the 2004.5 add a cat? I can't remember what year added it.

1. I believe my final drive ratio was found somewhere under the hood. In a manual transmission, speed is directly proportional to RPM, so we should be able to determine your ratio if you post what speed/RPM you are at in top gear.

I read somewhere that my truck cruises most efficiently at around 1600 RPM. With my oversized tires, tall final drive, and automatic, that's about 55 MPH.

2. The general rule of thumb for air dam is to have it hang down to the same level as the lowest component on the vehicle. That would probably be the rear differential.

I'm no expert on any of your questions though.

Hersbird 02-14-2017 03:55 PM

Today driving unloaded around town starting in 2nd, then just going 4th and 6th seemed to work pretty good shifting at 2000 rpm.
My truck has a cat or something between the turbo and the muffler that looks like a cat. It is a pretty beefy looking 4" system from the turbo back.
I'll do a 60 mph run after work to check RPMS.

I'm debating if I want to change all the fluids myself or just take it in. I think I just want to add gauges for lift pump pressure and EGT and then a Smarty JR basic tune and the bigger tires.

I was looking for an early 04 or 03 HO but they were either trashed or expensive. I was almost ready to go with a 01-02 HO but am glad now for the extra cab space.

Update: the RPM at 60 mph is about 1750 so that is 3.73 for the gearing. Those other tires would reduce that to 1665 rpm at 60. Or be the same as changing to 3.56 gears.

oil pan 4 02-14-2017 06:48 PM

Yes good idea the vp44 injector pumps and CP3 common rail pumps are very intolerant of low or no fuel pressure.
I'm not sure which the 2004.5 has, the difference is really bad and really, really bad between the 2.

redpoint5 02-14-2017 08:27 PM

I just remembered I cruise at 1600 RPM at 55. Revised my post.

Lift pumps commonly went bad on the gen II trucks, but I imagine the issue was addressed on the gen III. I got a replacement OEM "campaign" lift pump for cheap, but discovered it had gone bad after less than 40,000 miles. Before I installed a fuel pressure gauge, I would only discover the lift pump had gone bad after running out of fuel and then being unable to prime the fuel system (no fuel from loosened injectors). I had to buy an aftermarket lift pump since the OEM was so useless. Fortunately I have never lost a VP44, which is $2,000 compared to the $150 lift pump.

Does CR even have a VP44? I imagine it's a different high pressure pump altogether.

gumby79 02-15-2017 06:06 AM

Take your truck to a Dodge dealer and have them print out a build sheet, all the alphanumeric codes missing from the glove box . Some can some can't. They should be able to.
St Hellens , Oregon provided me with the print out were as Longview, Washington ~30mi away told me they couldn not even do it for a new truck much less my old 1991.5 .
If they can't call Oregon all they need is the VIN.
Anaconda was able to look up the info. Just was not able to tell me the part# for the large tank option listed on my truck after I put 27.011 ga in , from the trip in my signature.base tank is 27ga but may have the 35ga w/27ga sender.
Cummins Northwest is there in Missoula .
I contacted [url=]The Sensor Connection /url] and they said a simple 2pole x throw rotary switch would alow for extra K-Type probes for measuring other Ecomodder type things like IAT /grill block effects. Also the exposed tip probes(quick response) are ok on diesel they will just need periodic cleaning, I'm at 50,000mi with no loss of response speed. They have 2 fast response probes, a 250ms and a 125ms. Standard diesel is 1200ms or 500ms and shrouded. (Fail proof)
98-02 24v was the vp44 . You have the CP3.
Maby swap out the round tube steps for some that are solid like mying, run them all the way to the back tire. 1 ti gives a flat surface th hang skert from. 2 it will help keep the turbulent air under the truck insted of wrecking the flow for the hole lower side of the truck.

Dreem big chisel down to reality.

Hersbird 02-16-2017 11:50 PM

Well I had the chance to take a little 40 mile trip after work. Reset the Lie-O-meter from a dead stop but full warmed up, accelerated to about 58-60mph and held it there the best I could. After going through 2 small towns but catching the lights and turning around and going back 20 miles it was reading 33.5 average over 40 miles. Now that may be a lie but even if it is 10 mpg off it is still pretty freaking sweet. This is on winter diesel no less although it was 45 degrees today. Speedometer seems close according to one of those radar speed signs and my GPS, it may be reading 2 mph low at that speed. I did fill the 35 gallon tank but not until after that run, it may take awhile to get a hand calculated number and I'm back to probably just driving around town, and short trips anyway.

Hersbird 02-18-2017 08:04 PM

I got an above 50% set (8000 miles supposedly) of 275/70/18's mounted and balanced off a 2016 for $290 so that will be my first change. I am going to go as is for awhile and try and get more baseline. See if I can get my torque app dialed in as it is way off for some reason on this motor. Maybe even try an A-B-A test or at the minimum an A-B test on the same day, same course. Use GPS speed as the speedometer will be off.

slowmover 02-19-2017 06:31 AM

Scale it, Hersbird. As in my post to you on skykings thread. Data collection. And best tire pressure FF/RR.

Mechanical condition is uppermost for these trucks. Confirm that post-2008 steering conversion has been done and that balljoints (every 70k) have been recently replaced. All book maintenance thru 300k. Recent valve adjust? New boots on CAC system? No caliper drag? Perfect alignment? (See rdefayette posts on same at CF). Mech malfunctions hide underneath disciplined driving. Skew results.

As in another thread: how many years will you have this truck? How many miles annually? (Come up with something). Ownership CPM per worksheets at Edmunds or AAA (True cost of ownership).

Given X-miles annually, at an estimated Average mpg, what is annual consumption? What percentage change to the annual average would produce a $1000 savings? (Work these type questions).

Second, as skyking and others have noted, about the only effective changes are aero for highway and final gearing. If the vehicle sits around waiting to pull a travel trailer, changing to 3.42 will work against you. If the vehicle is mainly a commuter (where pulling a TT is 30% of total annual miles) a final gear change may be effective. And then it depends on TT aero and weight. Plus terrain and climate.

A-B testing. Keep it simple. Same pump before/after same 1-200 mile highway loop. On cruise control at 60-mph or lower. Truck empty, truck with more than 1k payload, and truck with trailer both loaded for camping trip. (Simulate passenger weight). The percentage change between these different states is what matters. Not the numerical mpg. Use engine rpm to set cruise at same spot on highway entrance ramp.

Cruise control is "assertive" on these trucks. Assumes truck is under a load. Let it do its thing in any state. It's reliably regular, overall.

Steering and tire choice if bad is 4-mpg easily. To the annual average. A greater effect than tank by tank (which is pretty much meaningless). Without "like new" mechanical condition per steering, front end and tires, "testing" is a time and dollar waster.

Were it mine I'd be looking at replacing all fluids filters belts and related. U-joints. Front axle bearings. (and further as in that post).

Rent a steam cleaner to get underside and repaint where corrosion has started.
New exterior lamps, etc. A copy of the state inspection form to thoroughly go over details.

There are some potential suspension improvements for handling/steering, but they also limit wheel travel some feel necessary for 4WD. How will you use yours in that regard?

Pics of your camper, or similar to what you want to do would be a help. Neckover goose type. 5er hitch? Conventional? Probable weight? Etc.

Congratulations on a fine looking truck!!

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