2400 rpm at 75mph... is this normal???

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dehdlee Duo

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Hey all haven't posted in a while but wanted to find out what to do.

I have a 99 Ram 2500 cummins 5spd, running stock 3.55 gears with 285 75 16 tires. The stock tires are 245 75 16's. When driving on hwy at 70-75 I am still getting 14-16 mpg but my rpms are like 2400. Is this ok to run? I plan on not going any higher than 70 in this truck. We are also looking for a trailer to tow with for trips.

Would it be a good idea to get near gearing? I have heard if I went to 4.10's it would make my rpm's jump. What is a good idea? I am stuck...

Thank you all in advanced for information.
 

gtomike60

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If you go to a 4:10 gear,your rpms will be higher than with the 3:55s you have now
You need a taller gear(numerically lower) to drop rpms
A taller tire will lower your rpms if there's room for them
 
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dehdlee Duo

dehdlee Duo

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If you go to a 4:10 gear,your rpms will be higher than with the 3:55s you have now
You need a taller gear(numerically lower) to drop rpms
A taller tire will lower your rpms if there's room for them
So would it be good to go with a 4:10 and a 35 inch tire for towing? I want to keep my current tire setup since it is perfect for how I want it to look. I am not wanting to spend more money if I don't absolutly have to. I am working on getting a chip so I can use towing options and better performance so I am not worried about gearing since it is a big job.

I will be getting an exhaust and Fass fuel system to help with those pesky gen 2 issues.
 

PaPitt

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What issues are you talking about on the Gen 2's ..
Pesky issues ..
I'm going to say GEN2'S DON'T HAVE ISSUES .
i WORKED FOR A DODGE Dealership for 11 years back in the service dept.
Now the dodge 2005's up until about 2010 sure had bad nasty issues.. Fuel systems killing motors . Is that the issues your talking about .
........ But the loud diesels motor didn't have the fuel issues. It was after the Quiet motors came out .
 

Rob2gen

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Long time ago my 98.5 2500 12 valve 4x4 Auto reg cab (bought new) had top speed of 82mph with OEM tires and chrome rims... had 4.10 gearing and got about 17mpg, mostly highway miles. Trying to remember the rpm's for that speed but 2800 comes to mind. Switched over to a 33 inch mud tire and Eagle rims and top speed increased to 87mph.

Wish I still had that truck.
 

LameUsername

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What issues are you talking about on the Gen 2's ..
Pesky issues ..
I'm going to say GEN2'S DON'T HAVE ISSUES .
i WORKED FOR A DODGE Dealership for 11 years back in the service dept.
Now the dodge 2005's up until about 2010 sure had bad nasty issues.. Fuel systems killing motors . Is that the issues your talking about .
........ But the loud diesels motor didn't have the fuel issues. It was after the Quiet motors came out .
He is talking about the VP44 fuel pressure issue with the stock lift pump, and I really don't want to slam you but the way you describe loud and quiet Diesel "motors" I highly doubt you did anything other than stocked parts at a dealership.
 

LameUsername

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Hey all haven't posted in a while but wanted to find out what to do.

I have a 99 Ram 2500 cummins 5spd, running stock 3.55 gears with 285 75 16 tires. The stock tires are 245 75 16's. When driving on hwy at 70-75 I am still getting 14-16 mpg but my rpms are like 2400. Is this ok to run? I plan on not going any higher than 70 in this truck. We are also looking for a trailer to tow with for trips.

Would it be a good idea to get near gearing? I have heard if I went to 4.10's it would make my rpm's jump. What is a good idea? I am stuck...

Thank you all in advanced for information.
Those RPM's are normal at that speed with that generation truck, My 95,96 and 99 with 47RH and 4.10' would run those RPM's with stock tires. I put 35's on all the trucks to bring it down a little.
 

PaPitt

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Well Lame.. you name fits you so well.
Service department all those years. Had 8 techs working.
.......................
...... When I left I had over 200 phone calls to my cell.. THANKING ME FOR MY SERVICE. & They said they could alway appericiate how I explained their situation. Even when It wasn't what they wanted .. They believed me in what i EXPLAINED TO MY CUSTOMERS .
......
Lame please don't turn this web sight into an bickering name calling sight like Pirate4x4 .& some others. This sight does an excellent job of helping . New members Build their Rides. I've been a member here for many years . back before this sight was bought out & started over. I joined somewhere about 2007. & My 1972 with a 4BT CUMMINGS in it .. WAS BUILT WITH a lot of help & Parts purchased from members from this sight. & I believe it's been running & driving since 2010 . It's very handy on my Farm. I used it about like a tractor. Dragging trailers, Hay rakes, Grain Drills, Hunting & SIMPLY Cruising the Pastures & Country roads..
Now go add some quality info to your 3 post..
Thank You.
 
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dehdlee Duo

dehdlee Duo

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He is talking about the VP44 fuel pressure issue with the stock lift pump, and I really don't want to slam you but the way you describe loud and quiet Diesel "motors" I highly doubt you did anything other than stocked parts at a dealership.
Thank you all for the comments. Sorry it took a while to get back. It has been a busy year and I haven't gotten to see these latest comments.
I totally beleive it was a big issue with vp44 but I have done some things to help it. Just put a new 100gph lift pump with a manual boost elbow, and have been getting 22MPG the last 3 months.

Daily driver and putting about 550 miles a month on the truck. So overall the MPG is doing great for what I have. the 4.54 gears with the 33" tires seems to put the milage different which I thought I would get worst milage. It is weird how it works.
 

PaPitt

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I thoiugh you had 3.55 gears.. In you last post you've typed 4;54's ..
I expect you do have 3:54's .. Those were normal..
You've got one of the best truck out there .. Be careful as to what you do to your truck.. & If you do change the rear axle I'd say save you old REAR AXLE BECAUSE YOU MAY WANT TO REINSTALL it after you find you don't like your changes. & You know yoiu old one is good.
.........
.......... I've never seen a fuel pump increase fuel mileage any.. So If you got your truck to 22 mpg.. Give yourself a big pat on the back. I've just installed a new rebuilt injection pump on mine. Because mine has alway gotten ''what i call terrible fuel mileage'' for a 2000 24valve. Mine get's maybe 14.5 on a good day.. & AFTER THE NEW injection pump . 3rd on by the way, I installed 6 new BOSCH INJECTORS ... THE MAN that owned the Injection house I'd don't business with for 40 years .. For my Farm & tractors & my Automotive store, I sent my pumps to him for him to rebuild .. But he recommended new injectors. I truly didn't expect them to help at all.. As we never replaced a set of injectors at the Stealership.. only the bad ones.. I even went back to one of the main 2 Diesel techs. No. 2 HAS PASSED AWAY. So I could ask him how he felt about replacing the set of injectors.. He was like me we never did that. But a new set since your man is giving them to you at his cost. can't hurt anything. Nothing changed at all. I'm still at 14.5 .. I've owned my truck since 2004 & this is what it's alway gotten .. The absolute best I've ever gotten was 18.9 FILLED UP & jumped on freeway flat run empty. & i DROVE ABOUT 300 miles cruise set @ about 75mph & Got off & filled again before I started a different section of my trip.. Winding road & up & down different mph & I got about 15 2nd trip. ALL Figured with the calculator. Not from the overhead. .
My truck doesn't get decent /good mileage. AS I Worked at the dealership I ask everyone what their truck go for mileage. Everyone told me theirs got from 16.5 to 22.5.. not mine . AS I said I worked there for about 10 years & We were the largest diesel truck dealer ship diesel shop in Texas.. DESPITE what Lame thinks .. my Noisy diesel get BAD MILEAGE.
........ But be careful with some changes .. Yes I now have a chip on my truck. Funny only thing I think mine does is I think it made mine Noisier. I can't tell it changes anything. Mine had a setting for 25hp 50hp 100hp more. & Fuel economy or one for pulling. I've never noticed any difference. That tech that passed away He swore by this one & He pulled it off his Truck & installed it on mine .. Just before he sold his truck as he knew he had cancer, & would not be with us much longer. SO i PAID HIM & shock his hand & told him thank you.
....... I'd sure be interested in any things you've done to your truck .. those that have helped & Those that haven't helped.
You mentioned buying a trailer . I'm going to say The size of the trailer will determine a lot... My truck 50 % of the time is hooked to a 18ft car/ tractor hauling trailer.. With either a samll 841 Ford tractor on it, or My 72 Bronco wt. about 6000lb. Because of the Cummins 4BT in it & all the wt. i keep in it. Or i also pull an 18ft cattle trailer with 2 or 3 cows in it. Or I have a 32ft flat bed with a Pick-up camper extended over the neck of the gooseneck & THEN some Bronco or tractor going to place in New Mexico It's a 555 mile trip one way. My truck gets 9 to 11 mpg going out there & 11 to 12.5 or 13 coming home down hill. Been doing it for 25 years now. 1st trips were with an old 1990 12 Valve .. On the floor all the way. app 65 to maybe 72 a few miles .. It didn't have an O/D trans. When I got the 24V WE Felt like it had twice the power. While i Still Love my old truck I wish it could get better mileage.
 
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