24V Reliability

[srawleigh]

I have been reading posts for several months on the 24V Cummins. I need some guidance, because what I am reading concerns me a little.



First, a little history. I am not new to the TDR. I was a member when I purhcased my 94 4X4, SLT back in late 93. No website then, but the mag was great and the members and information exchange was fantastic. This was helpful to me because this was my first diesel vehicle. Unfortunately, I had to sell my 94 due to changing family and work needs. I told my wife that i WOULD own another Cummins, I would just wait for the right time. She agreed



The time is getting closer, so I am beginning my research and catching up on all of the changes relative to my 12V. Hence my questions: ANy insight that this great thread can provide will be appreciated.



1. It seems like a lot of people have problems with lift pump failures. I am not familiar with the current engine architecture, but I ran the heck out of my 12V without any problems. What gives with the lift pump problem. There seems to be a lot of dissention regarding the solution. How bad is the stock pump? Is it best to replace it with a single, higher performance pump? Surely, Cummins should be addressing this problem.



2. Why did DC start offering L/S rear only with 4. 10 gears in 2000? I had 4. 10 in my 12V and I am not sure whether I need them or not.



3. Anyone live in the mountains and drive with 3. 54 gears? I will be looking for a used 24V and I would like some opinions on 3. 54 versus 4. 10. I do not tow, but I do travel in the mountains with light loads (up to 2K lbs). I plan on putting 33in tires on the truck for some additional snow clearance. 33 in tires will act like an additional 7. 5% overdrive. How badly will this affect the 24V since the powerband is a little higher in the RPM range that the 12V? I plan to purchase a 6-speed (prefer) or a 5-speed.



Thanks for you help. I look forward to becoming an active member of the forum.

 

[dresslered]

First of all, I don't know why people keep thinking that you can only get LSD with the 4. 10's. I have the LSD and the 3. 54's and mine is a model year 2001. The 3. 54's will also work just fine in the mountains. The only reason that I would ever go with the 4. 10's is if I were going to tow extreme loads or I was going to install much larger wheels (then do the calculation). I too am concerned with the lift pump. I think that after I get my new one replaced under warrantee, I will then install it in the back where it was suppose to go. End of problem. Good luck with your decision.

 

[Cliffman]

Lift Pump

Lost my lift pump at 45000 miles while on a trip to Colorado. Good thing I had the replacment pump in the tool box . I now have 20K on the new pump and I'm told this pump is the "revised" pump. No drop in preasure since I installed it.

 

[LSMITH]

The lift pump is a problem on a lot of trucks. Putting in a gauge to monitor the fuel pressure is the best way to stay on top of it. I have not heard of a lift pump going out that was fed by a pusher pump, but have heard of several of the different pusher pumps going out. The lift pump going out is not a truck stopper but it needs to be changed ASAP when it dies.

I have the 3. 5 gears with the LSD. I would not want to drive a CTD without the LSD either. I run a tire that is 33" tall and with the factory auto trans setup it is a little too tall. If I had a manual trans I think I would be happy with the gear/tire combo. I have run it in the mountains and there are no problems with power. If there is a chance that you will go taller than the 33's and are not going to bomb extensively then get the 4. 10s IMO. 35" tires and 4. 10 gears would be the ticket for me.

 

[HC]

Ahhh, chance to share opinions. Thanks for asking!

(some of this is from reading past posts, just greatly summarized) (edit - just reread my own post - scratch the "greatly summarized" part )

My rig, 2001, HO, 6 speed, 3. 54 and no Limited Slip (sort of)

1) Lift pump - 76k and still going. I'm nervous as a cat on a hot tin roof because I don't yet have a fuel pressure gauge, but very soon I will, and will buy a spare pump for the tool box before my next out of state trip. I feel no need to relocate or rig pusher pump with my stock fueling levels - I just think I need early warning because I know sooner or later it will go out and I don't want it to take the expensive VP44 with it.

2) Rear end - harder to call with the 24V; some people even believe the higher rpm range of the 24V gives 4. 10's the edge on mpg. Long threads on this if you search. I personally am very happy with 3. 54; at 2000 rpm I'm right at 71 mph. 4. 10 would put me a little over 2300 rpm at 70. If you're getting 4WD getting Limited slip is debatable. I've basically got the same tires that came on the truck (not counting road damage the first month), and no LS is part of the reason why. But then I added an ARB locker so that I could have my cake and eat it too. My main point is that if you get an open diff and decide later you screwed up, there are many excellent after-market upgrades, from selectable lockers, to lockers, to limited slips. It cost more after market, but you get a better product, too.

3) Mountains / 33" tires / rear end - Even with 33" on 3. 54's, if you get the 6 speed then in 5th gear you at 2000 rpm you'd be hitting about 55 mph. 5th, direct drive, "babies" the transmission, so that sounds like a good combo to me for mountain driving. In 6th with 4. 10's, you'd still be at 2150 rpm at 70. I use 1st to start off unless I'm holding up traffic, so my clutch is babied, but if you like to launch in 2nd (as most folks do) then 3. 54's + larger tires would probably shorten your clutch life some. This one is too close to call - I could go either way. If you think there's any chance you'd go bigger than 33" in the future, the scales would tilt to 4. 10's. Bottom line is probably your driving style - how fast do you like to drive, most of the time?

If you're a back roads "slow cruiser", 4. 10's might be best, if you like to get in the hammer lane and pass folks on the freeway, your engine is going to like the 3. 54's. I'm more the cruiser type, and I'm happy with 3. 54's, but I don't have the bigger tires (yet).

 

[srawleigh]

Thanks for everyone's reply. Eventhough I would like to get 35s for my future TD, I don't think my wife will go for it. I am sure many know about this factor. So realistically 33s are it. I had 33s on my 94, Auto, 4X4, and it seemed a little strained at 70mph. Then, I realized that these engines like to be run. I just don't want to be "lugging" the engine at 55-60 if I get the 5-speed due to the weak 5TH gear.



Why isn't the fuel pump located in the fuel tank like most gas engines. Doesn't it make sense that it is easier to push fuel from the tank instead of pull it from the engine? If not in the tank, at least place it next to the tank.



Does anyone know of a good diesel shop in MD, near Baltimore? I have had limited experience with a Cummins shop in Landsdowne (Chesapeake Cummins), but I had no problems with my 12V that required real intervention. At least my Dodge dealer had a dedicated Diesel Mechanic.



Are there any other real issues on the 24V Dodges that I should be wary of?



What are ETH, ETC engines? The difference and how can I tell the difference? Is one more desireable than another?



Thanks again for your help.

 

[Scooby]

ETH is the option code for the High Output engine (only available with the 6 speed transmission: option code DEE) The HO puts out 245 horses (I think) and 505 ft lbs of torque as opposed to the ETC engine ("the standard engine" available with the 5 speed and auto) which puts out 230 hp and 460 ft lbs.



(Some one may want to check the above numbers, but I think they are correct)... . you get the point, though, I'm sure. Get the HO if you want a manual truck!

 

[csutton7]

srawleigh--bingo on the pump location---this is the reason we think it fails and some guys opt to relocate it back by the tank and others opt to add a pusher pump to assist the mislocated thing----the only other thing on 24v is maybe the auto transmission once you start to BOMB and even if you didn'f BOMB it wouldn't hurt to upgrade the T/C and valve body---oh yea maybe the 5th gear nut on the manuals-----and Dresslered is right on the LS and most guys are happy with either the 4:10's or 3:54's-----chris

 

[Jack in Alaska]

Original lift pump and 87k miles.

14 psi at idle; 10-11 psi at WOT and steady. But I worry about it.

 

[ralphr]

I have 99 with 3:54 LSD, no problems, if towing in mountains then 4:10 probably would be better option.



As to the lift pump need to monitor it, (see my post on "lift pump probs"). Just because you have acceptable pump pressure do not assume pump not going bad. In tank pump, move pump close to tank? I do not think that is the problem, in tank pumps relativley new most vehicles I ever worked with mechanical pump on the engine, almost never had problems with that set up! I think pump design not good, mabey revised pump will better handle situation.



just my $. 02 good luck.

 

[Cliffman]

Dieing Pump

When my pump was on it's way out it went slowly. PSI gradually dropped until about 6 psi at idle pre filter and then it just quit.

 

[RADdodge]

Mountain Driving and Gear Ratio

Before I purchased my 3500 (auto), I wanted to know which would be better suited for my application, 3. 54. or 4. 10. Knowing that I was going to a bigger tire from the start, I believed I wanted the 4. 10, but wasn’t sure. So I built a spreadsheet and input the factors and looked at the graphs. That helped me decide.



My tire diameter is now 35. 1 inches. With the 4. 10 I wish it were geared a little lower yet. In the mountains, there have been lots of instances where I have to shift out of overdrive because I fall below my peak torque rpm at about 62-63 mph (usually due to slow traffic!). I have no problem maintaining any legal (or safe) speed on any grade I’ve encountered, the truck has plenty of power, but I don’t want to push (read lug) the engine below about 1600 – 1700 rpm. That translates to about 62-63 mph. On the open highway, I hit about 72-73 mph at 2000 rpm in OD.



I’m including a screen shot of the Excel Spreadsheet (800x600) the shows the truck with 3. 54 gears and standard wheels compared to a 4. 10 with 35 inch tires. I’m actually about the same mph at rpm as the stock configuration with 3. 54. The resultant ratio shows 3. 69. That’s only true compared to the new ratio, which is 4. 10, not compared to the 3. 54 ration. The formula is old tire diameter/new tire diameter X Gear Ratio (4. 10). The actual effective gear ration when compared to a 3. 54 is something less that 3. 54! For example, at 1800 rpm, with 3. 54 and standard tires, the speed is 62. 6, with 4. 10 and big tires the speed is 64. 3. I’ll leave it to you guys to draw your own conclusions.



#ad

 

[srawleigh]

RADodge -



A couple of thoughts here. There are several factors involved. Static Radius vs. Rolling Radius. Tires are typically not the actual size that you calculate based on the information provided by the manufacturer (typically smaller) which would lend itself to a numerically lower ratio. Also, tire pressure makes a difference as well depending on what you run. All of these factors can make a difference. The best way to determine exactly is to run a measured mile.



Thanks for the information. This will be helpful in making my decision.