I am at 1500rpms at 60mph in OD. This makes little sense for any diesel IMHO. However I dont want to go to 4:10s as this will make 1-3 to low geared for me. SO, would going to a smaller tire make any significant changes? If I lost say 2-3" overall diameter. I would like to get it in beginning of power band IE 1800 when it automatically shifts at 60mph. Right now it is "bog" city and that by design. For what we pay for these things you thing they could get more than the engine right the first time.

 

get an EZ or something... more fuel... never go backward!

 

Yes the smaller tire would help but I second Forrests opinion and get a power enhancer I would suggest a Smarty as it has many options including a fuel saver mode.

 

I have the same rear end and was disappointed just like you. I bought a Superchips 3705 programmer and it made a huge difference. Some will say get a Smarty but it's twice as much as my Superchips and I'm not a performance junkie so my set-up is serving me well. If I had it do over again, I would buy an Edge Juice with Attitude because the price of my gauges and programmer are about the same as the Edge and it looks much cleaner to me.

 

I have a edge ez on order. I have a stock tranny and want it to last. I hope this will make a difference. Probably the only other upgrade may be 275rv injectors in time. I want to see how the edge ez does first. I dont have the bomb bug. Just want to pull my camper without "bog" in OD.

 

I have no bog with my set up. I also have 3:55 gears. No problem pulling my boat around. 25' bayliner. But I think my transmission is maxed out with my set up.
My next addition to my truck is going to be a valve body and a torque converter.

 

Do you have guages? They really help in diagnosing problems. You also had better get them once you start fueling it with a box....

 

One mans poison ...is another man 'happy' pill! But the .68 ratio on OD is a tall gear! (about 100 rpm higher at 70 mph than 6th gear on the HO's.)

I love being at 2000 rpm at 80 mph with 315/75/16's; I keep OD locked out below 2100 rpm at all times.... and averaged 17.3 mpg on my last 1,000 mile test.

I agree with the others, more power/tq will make a difference and smaller tires will help some, too.

RJ

 

SSweeney - I had a similar problem as you when my truck was stock. But I have a 6 speed. I have the Edge EZ with elbow, RV275's, no muffler or resonator. I've been running this way for a long time. I have plenty of power now, and have slipped the clutch 2 or 3 times. I'm at the limit of the clutch.

If I were you, before you spend the money on the RV275's, I think I'd bomb the tranny. Auto's are nice, but a stock one won't take much much more power from the engine without complaints.

- JyRO

 

Thanks for all the good input. I am looking forward to the edge ez. I do not think I will upgrade above that until I get at least a TC and valve body. RJ, not sure if I understood but I would have to run 3rd gear up to 2700 before I could engage to OD. I would rather not rev it that high for long periods. I just wish I could get it at 1800rpms at 60

 

I'm a little confused. Was thinking about this thread on my way home so I checked... I'm also at 1500 rpm at 60 mph; but that's with 315 tires???

My point above was, you won't hurt anything cruising all day long at 60 mph with OD off... including mileage. JMO!

RJ

 

Hi Sweeney
I`m at 1800 revs at 60 and have a 4.10 rearend.If you want those revs at that speed the only way to go is fit 4.10 gears.

 

Hi sweeney
Just looked at your original post.
If you fit smaller tyres to lower the gearing in OD you also lower the other gears by the same ratio,plus I think smaller tyres would look a bit naff.If you fitted larger tyres so as to hit 60 out of OD at reasonable revs I think you would notice some loss of flexibility in power delivery more so when towing.
Also lowing the revs at any given speed will almost certainly increase the amount of torque through the transmission,and what I`ve read on these forums the auto box is not the strongest without some mods

 

Thinking back on your original post, 1,500 rpm in O/D makes sense for a Peterbilt.

I am assuming you're in "bog" city when towing. Because if you're concerned about 1,500 rpm at 60 mph when empty ... don't be. If this is regarding towing, the quick and easy thing is to reach up and lock out O/D in situations where the transmission may cause, or has caused a "bog."

Maybe pushing this button is a bit of a nuisance, but I can't imagine its anywhere near half the involvement a driver must be committed to, when rowing 5 or 6 gears. Push the button. So you'll be turning, what 2,100 rpm at 60 mph? Great! Plenty of pull, the economy is still good in 'D' versus 'O/D' at that speed, & when you're ready to pull, it'll shore do it at 2,100 rpm.

Once you've got the rig up to your max towing speed, and it looks like you'll get to stay there for a while (like on the interstate), unlock the 'O/D.'

My truck already looks like the tires are too small. If yours is 4WD, its going to look a bit funny with smaller tires.

- JyRO

 

This is what I do. At first I did not like to run my truck over 2000 rpms when pulling but one day I decided to give it a try on a pull to the lake. I locked out O/D the whole trip and ran 1800-2300 rpms the whole trip. At first it was noisey (straightpiped) but I eventually got used to it and then it didn't bother me...I actually liked it. Man what a difference. It pulled better than I could have imagined and my mileage was actually better because it wasn't having to work as hard. Now if I get on interstate then I will unlock OD when I hit 2100 rpms.