eightball

I'm a newbie owner of a 2005 cummins Dodge SLT, 4x2, Quad, Long bed.

I was taking my new truck on a trip up to the California Sierras from my
home town of San Jose, Calif. I tried the tow/haul mode, but the engine has so
much torque and H.P. that it didn't want to down shift out of O.D. even when climbing
some pretty sustained, steep, grades. It did however down shift mometarily when
turning on the T/H mode while in cruise control at 60-65 mph. but would go to
over-drive with-in a few seconds, as the engine apparently wasn't laboring.

Now, this is my question about the T/H mode while going down-hill from the Sierras.
I had my cruise set at 60 mph. and when I was on a sustained downhill grade tow-haul
would downshift the tranny into a lower gear if my truck started to coast just a few
mph. past the pre-selected cruise control speed of 60 mph. I thought that was
pretty cool.

I don't remember my cruise control cars or other vehicles down shifting when the vehicle
started to exceed it's pre-selected cruise-control speed because of gravity. I tested
this by taking the truck out of T/H, and when the truck started coasting past 60 mph.
there was no downshift to brake the speed.

I am excited about testing this function when I have my trailer on the rear-end. It isn't a heavy(3,400 lbs), but it will be interesting to see what T/H does, and how effective it is.

By the way, is Over Drive a 5th gear. or is it 4th, and when T/H mode kicks it down from O/D is it going into a 3rd or 4th gear.

Got 20.6 MPG......with mountains, and freeway...........whoopee!

ASHNBAK

I just got back from a 2,000 mile trip from Lakewood, CA to Winchester Bay, OR with a combined weight of 21,000 lbs. You can shift out of OD with the T/H button at 67 mph (4.10 gears) and it will stay there until redline or you let off the pedal. I also did the same for grade braking, engage the T/H button at 65 mph going downhill and it will hold 3rd until you apply the throttle.

pecandude1

i just wish it would let you lockout overdrive when you need to

eightball

I thought that the sytem in T/H will only stay in Overdrive if the engine, and Tranny are
handling the load withing tolerable limits, unless theres tranny overheating, or engine
lugging. If the engine starts to lug a little while in T/H, doesn't the Auto Tran, downshift
out of Over Drive?

What your saying is that you don't want it to upshift back into O.D. even if you hit
some flat stretch where the engine can gear up and give you better economy, and
the Automatic isn't being over-heated?

By the way, is the 48RE a 4-speed with a 5th over-drive, or it the over-drive 4th?

bigblock2stroke

Hopefully DC will release a reflash for the 04's (with the right ECM) and 05's that updates to the 06MY logic. Hit the button once and you get tow/haul mode (and the light on the dash). Hit the button again and it will lock out overdrive. I believe there is also a 3rd logic set for when the exhaust brake switch is energized.

48re is a 4-speed trans 3rd is 1:1, 4th is OD.

SolarRam

Is there a way to get a higher gear? I spend alot of time driving 80 mph on a reasonably flat highway with no load just empty. Can it be reprogrammed or is there some aftermarket part available?

bigblock2stroke

Reprogramming definitely won't help you gear ratios.

I put bigger tires on mine and reprogrammed the speedo.

There are also gear splitters (I think the company is call Gear Vendor).

Do a search on this site for either and you should find a lot of stuff on numerically lowering your final drive ratio to get lower rpm's at high vehicle speeds.

bigblock2stroke

How do you like your airbag suspension?

Is your truck a 4.10 or 3.73?

It's not in your signature.

bigblock2stroke

Sorry I didn't see that you already have different rims/tires.

Did you get your speedo recalculated?


If so, what engine rpm are you turning at 80mph?

bluepp

The gear vender is sold and installed at ( Camping World ) US GEAR also makes one that used to be sold and installed at Camping World

hammerjammer

the 48re ,when going down hill,with cruise control off will down shift into third gear when the tire speed is too fast for engine rpm's ,or when you apply the brakes to slow the truck down,the 48re is a pretty good tranny,just needs another gear and for some applications,the ability to lock-out Od.The 48re is a 4sp.,overdrive is 4th gear.

SolarRam

I did go a little bigger with the tires and yes have adjusted the speedo.
I have 3:73 rear end so at 80mph I turn 2250rpm.
The airbags are great, I only run a couple of pounds in them empty and it rides like a car.

Do the gear splitters split all 4 gears? How many shifts up etc... I guess I would like to lower rpm, temps, and noise and maybe increase mpg. Is that possible?

bigblock2stroke

I actually don't know alot about them. I think they split all 4 (high/lo range)

From what I've heard they do work for lowering rpms and getting better fuel economy. Not sure about temps, but it makes sense.

Pretty spendy though (I think $3k+)

I sure would like to try the airbags.

JPDiesel

Just wanted to say hi to eightball:

I loved San Jose. I was stationed at Fort Ord (before the closure). Would take a trip to San 1 time a month. Love the Cali weather!


What a great rodeo, lots of pretty ladies....sorry for stealing the thread. Just having some flash backs

yfz450guy

what about a 2 speed rear axle? that would be awesome.