Engine/Transmission (1998.5 - 2002) Towing in OD Auto?

[ShawnC]

This is my second Cummins Ram Auto, the first being a 1993 12v Auto 4-Speed no lock-up converter. I towed in OD no problems. My new 2000 has the lock-up converter for OD I have always been under the impression that you don't tow locked up or you will burn out the trans. So I don't and my mileage shows it- 12mpg towing 14,000 lbs of Fifth Wheel. Now I know that isn't really bad but can be improved in OD. (See sig for truck info. - Jasper trans has planetary gear, waffle plate and clutch plate upgrades) I'm pushing 3,000 RPM doing 65-70 with load. So I drive a little slower for mileage. Or spend the money to save the time and pay as I go.

So to OD or not to OD that is the question.

 

[champspa]

I always use over drive when pulling a trailer and it's hard on a converter that's why I have a triple lock but my mileage isn't any better than yours. the goose neck and tractor weigh 16k plus the truck makes a total of 23k or maybe just a little more. that's about the right mileage for that load. I'm for going it in Overdrive and getting a torque converter upgrade .

 

[cerberusiam]

You need to tow in OD. In drive you are so far out the power band its just wasting fuel.



Since you have a few upgrades in the trans it should hold provided Jasper didn't mess the build up. With the weight you are towing the TC is going to be the weak link, especially lockup. As long as the clutch doesn't slip your ok until the power\heat\weight starts tweaking the cover. If the trans doesn't have a shift kit that would be a big help to keep things from slipping and starting the problems.



A triple disk TC in your case would be a good investment.

 

[Vaughn MacKenzie]

Shawn you are more likely to "burn it up" unlocked than locked. But if you are towing in Drive vs OD the trans is still locking, which is much better for it than towing unlocked. You would be creating more heat with it unlocked.

But since you have 4. 10 gears you should be able to run locked in OD most the time as long as you're on flat terrain and not bucking a headwind. When your RPM gets pulled down to 1900-2000 RPM then kick OD off and let it wind up until your speed increases, then shift back into OD.

Leaving OD off is mostly recommended for those with 3. 54 gears to prevent lugging.

By the way, I would love to get 12mpg towing 14k. . . both of my 12-valve trucks get that towing half that much weight, at low-mid 60s MPH.

 

[Ram4Sam]

If I was towing that much weight and getting 12 mpg with an auto, I wouldn't mess with it. That is great mileage for what you have. If you can improve on that, please let us know how you do it.



Sam

 

[ShawnC]

Thanks for the responses. I do think I'm getting decent mileage but we all want more, especially with the godsend mileage some post - usually 5 and 6 speeders. My 93 was a 3. 54 and I towed a 6-7000lbs ball hitch getting same mileage as new set up, 12 tow 16 livin', but towing twice the weight and a nicer interior now.
Big Hoss was originally set to level 5 just took down to 3 have not towed yet or enough miles notice improvement.
I'd love more responses and mileage experiences, thanks again.

 

[cerberusiam]

Your not going to make much difference in mpg as it takes x amount of fuel to make the power you need. It doesn't really matter whether its at 2000 or 3000 rpms. If there are gains to be made it will be at the lower rpms but that may be offset by the deeper gears.



TQ peak on the ISB 24V is going to be right around 2000 rpm's so the sweet spot will be around 2100. With the 4. 10's you should easily be able to hit that at a decent speed using OD. The 4. 10's are going to make it a lot easier on the transmissin also becuase the leverage is better, but, you need to get the TC locked and keep it locked as much as possible. These engines don't like spinning at those high rpms all the time. Duty cycle drops drastically after 2600 rpms and greater so the lower you can run and maintain speed the easier it is on the engine.



The algorithm that controls lockup is really crappy on these trucks and they unlock at the slightest hint of load. A lockup switch or controller with the extra power you have will allow better control. Since the stock TC is so loose the bulk of the heat and eventually the problems will come from spinning the TC in fluid coupling. Plan, build, and drive to maximize the time in lockup is the goal.

 

[B.G. Smith]

With the 99 I had with the 3. 54 gears I towed 5th wheel of about 12,000 lbs. in OD when I could keep the speed above 60 mph, at lower rpm it was easy to slip the lockup clutch. I have a little heavier trailer now and the 06 handles it fine in OD with the trans in tow/haul. bg

 

[gerry]

towing in OD

I have towed my loaded flatbed (5k) and toyhauler (7k) with 3:54 fd, stock transmission and now with a ''built'' trans: triple disk tc, kevlar belts etc, and now with Edge with attitude but always using OD where ever it would hold. My stock tc went at 93k so if I remember right the manual says never to tow in overdrive but I did and don't regret it. I do think the 47re is a bit weak for the 460 ftlb torque and my guess is Dodge chose to deal with it by saying not to tow in OD. Cheap way out for Dodge! My main interest is watching my coolant temp, which rarely goes over 205* but maybe even more important not letting egts go over 1200 for very long. If Dodge would have spent maybe $300-$400 more on their transmissions we would have had a much better truck IMO

 

[fstfish66]

i tow a enclosed car trailer,( like towing a brick wall) flat front 24 ft, with car inside its just over 7200 lbs,,stock 2002 5. 9 auto 4x4 i probably made a mistake ordering it with 3. 55 gears,thinking ide save fuel and lower rpm,s on the high way,,, i only tow 2 to 3 times a year,,but find it needing more power in the hills of va and nc,,i always shift out of O,D when climbing and keep it around 50/55 mph,,as i dont have a boost or exhaust gauge,trying to keep the turbo cool,,,and mileage,,whats that ???? terrible if you ask me from what ive heard from 12 valve owners in the past

 

[Jim Ross]

We tow a 27. 5 ft. Arctic Fox 5th wheel with a super slide and we do it in OD unless in hilly terrain. The truck has 3. 54 gears.
See my signature for the truck specs, but the trans has a Sun Coast TC + Sun Coast valve body w/shift kit + a BD pressure lock kit + Ams/Oil synthetic ATF. The engine has 275's + Edge EZ + Turbo Master that lets it spin to 30psi with the factory turbo. We get around 12 pulling the 5th wheel and over 20 empty if I keep my foot out of it. Getting rid of the muffler and putting on a 4" straight pipe lowered our EGT's by 125 degrees. Hope this info is useful.

 

[fstfish66]

wow thanks for the muffler trick,,,ill remember that next time it rusts out,,,

 

[DACoffman]

get a trans gauge and keep it under 220 you will be fine

 

[Jim Ross]

We had a transmission temp gage in our 7. 3 Ford and when towing the 27 ft 5th wheel in 90 deg temps on the freeway across Nevada, the temp was always in the 185 deg range..... when I dumped the fluid and put in Ams/Oil synthetic ATF the temp went down to 150-155 under the same conditions.

 

[fstfish66]

a trans temp gauge sounds like a winner,, and i have an open pod on the A pillar,,,was going to do the boost/egt gauge,,,dumb question,,,i never looked in to it, where are you picking up the fluid temp of the trans??

 

[JohnBoy5]

220 measured where?

 

[SnoKing]

I have been towing with a 2001. 5 with 4:10, complete DTT transmission, Jammer 1's, PDR35, large exhaust and Banks exhaust brake for years. I tow at around 20K combined weight. I tow in OD all the time at 2000 RPMs at around 63 MPH. I manually take it out of OD at 1800 or below. Bill coached me in the beginning about lower line presure to torque converter at at lower RPM's and not to apply gobbs of power at lower RPM's. I manually drive the transmission when towing, holding it in 3rd until I get up to at least 55mph before switching to OD. The DTT smart controller has a setting to adjust 3rd to OD shift. I have that set to 43-44 for non-towing shifts. Towing I override that manually to a higher point, which includes both directions. I down shift in the low 50 to 3rd to use the exhaust brake on mountain passes or freeway off ramps. I also assist shift by letting up a bit when it shifts, driving it similar to a manual transmission. Works for me. Bands have not required any adjustment in 50K and pan is clean at fluid changes. I use Amsoil transmission fluid.



The DTT smart controller has a setting to unlock the TC at higher throttle postions to protect the TC clutches from slipping. When it is unlocked then heat must be monitored and managed. I have transmission temp at the out line and in the pan(switch) and seldom have temp issue except in heavy stop and go traffic.



When I come out of overdrive to climb a mountain pass, I slow down to around 50-55 and climb the mountain at comfortable RPM's(2600-2700). 3000 is screaming!!!! I hate California and their slower 55 speed limit while towing. To slow for OD and to fast/busy for 3rd, beside being a menace on the road with all the faster traffic flying by.



Towing mileage varies between 11 and 12. 5. Has never been below 10 and has been as high at 14+(South Tahoe to California coast, up one hill and then down hill the rest of the way)



Snoking

 

[Jim Ross]

a sending unit can be installed on the transmission pan or on the line going into the transmission cooler up near the radiator

I had the one on the transmission pan, but it is more 'involved' to install than putting one of the cooler line.

Take a look in the Geno's catalog and see what they offer.

 

[JohnBoy5]

i had seen this very nice looking adapter ACU TEMP ADAPTER ('89-'10 DODGE)-Dodge Cummins Diesel Truck Accessories – Geno’s Garage but i would think any time you can get the sensor in the oil be with out intrupting the flow you would get a lot better of a thermal reading. i will work on something and see what i can come up with for this. i think the flow is much more important then the reading on the line. reduced flow = higher temps i would think. if i come up with something i will try and take pictures and explain what i did. i sort of have something in mind already.

 

[SnoKing]

DTT uses the 1996 or 97 output line that has a sender port in it and a custom extension to reach the cooler on the side of the engine. This allows one to measure output temps close to the output of transmission. Things happen fast at this measurement point. I feel the sender in the pan is a waste and have thought about moving to the rear diff.



Chris