Towing in or out of OD.

[JPLB22]

I've had my CTD for about a 9 months now. This sommer will be the first time for me to do a lot of towing. So if this is a stupid question, forgive me.



I will be towing a 7000# trailer. Now, when I'm on flat ground would it be better to be in OD at 60 MPH and doing 1500 RPM. Or would it be better to be in 3rd and doing 2250 RPM at the same speed. I'm just wondering what is best for engine and transmission.



My rig is pretty much stock except for a 4" exhaust. No transmission controler or any other transmission bombs. My rig is an auto and has 3. 55 gears.



Thanks in advance for any replies.

 

[JPLB22]

And also, would it do any harm to the transmission to tow 7000# at 80 MPH in OD on flat ground?



So for the two dumb questions.

 

[RustyJC]

Originally posted by JPLB22

Now, when I'm on flat ground would it be better to be in OD at 60 MPH and doing 1500 RPM. Or would it be better to be in 3rd and doing 2250 RPM at the same speed. I'm just wondering what is best for engine and transmission.

We pull a 13,500 lb 5ver. With 4. 10 gears, 70 MPH in 6th gear is 2350 RPM. The Cummins will run this speed (and higher) at 21,180 GCW all day - it won't hurt a thing except maybe your ears.



Rusty

 

[Dean Upson]

If you transmission has to "hunt", going back and forth between gears, then it's time to get out of od.



Dean

 

[lizzyhermit]

I pull a 30' TT engaging OD at 55-60 mph and dis-engaging OD at 60-55 mph. hard and fast rule... . and have "accidentally" gotten to 85 mph on a couple of loooooooong flat two lane stretches.

for comparison my actual weights are.



13280#'s GCVW

truck at 7560#'s (3680 rear, 3880 front)

trailer axles 5720 #'s



have guages, no problems indicated and we motor on down the road.

 

[RBSOB]

O.D?

Ditto Dean. Your truck will happily pull 7000# over most terrain in OD as long as RPMs are "up". If the transmission wants to down shift, let it run in 3rd, even lock it out on hills. I have no regrets for getting the 3. 55 gearing, its OK to run in 3rd and keep the RPMs up when necessary. Have a fun summer, Jim G.

 

[barryg41]

Run it like it wants to HARD!



Two summers ago I was running across S. Dakota. I left it out of OD and ran 68 mph. Which turns out to be right at 2750 rpms. That is what Cummins said I could run my engine all day 24/7. After talking to transmission guys here on TDR, they say run the rpm's up and keep the speed (throttle position) up. It keeps the transmission up to pressure and all.



That was back when I was all stock, except for gauges. transmission temps never got above 130 F. I live by the transmission guys telling me to keep the rpms and speed up.



Still on the OEM transmission and lift pump. No additives! 70K!



Barry

 

[Fireman Dave]

JPLB22:



My set-up is almost identical to yours - 3. 54 gears, stock power, 4" exhaust, 7,000 lb TT. My goal is to take the stock transmission as far as it will go. I have a trans temp gauge, and I change the fluid and filter every spring - regardless of miles.



One of the transmission gurus - whom I respect a lot - told me that towing with OD off is best. Other transmission gurus also say to keep the RPMs up above 1700, I believe. 60 mph in OD with our gears is right on that line, so OD off is a little more comfortable, in my opinion. I do tow in OD on long flat stretches at higher speeds - like 65 or so. But higher speeds = hotter trailer tires, so that's another issue to ponder. This summer I plan to tow under 65 mph (after loosing 2 tires on a trip last summer). Mileage will be better, and it's safer. Just takes longer - but hey - it's vacation anyway. Those are just my opinions. Some guys swear by towing in OD and at faster speeds.



By the way, once the stock transmission dies, I'll be putting in a built transmission and cranking up the power. But I hope that's a long way down the road.



Good Luck.

 

[JMichelson]

JPLB22

I tow a travel trailer with 3. 55 gears and an auto (BD). The combined gross weight of the truck and trailer is 13000 lbs. I tow in O/D at 60mph and 1500 RPM. all the time. I’ve even let it drop down to 55 and 1400 RPM’s or so on flat roads and no head wind. I keep an eye on EGT’s and don’t let it lug and watch the transmission temperatures which have never been a problem. If the transmission want’s to shift out of O/D on it’s own I push the O/D button and leave it out of O/D until I feel it will stay in O/D then I let it shift back into O/D. I have towed thousand of miles doing this and have had no problems. I find it nicer than running along at 2400 RPM’s I do get better mileage using O/D than running at a higher RPM. . With your trailer weighing more than mine this may not work for you, Jeff

 

[JPLB22]

Thank you for the replies everyone.



Fireman Dave, trailer tire heat is a great point to think about. In my very limited towing I have never experienced a trailer tire blow out, and I'm SURE I DON'T want to. I will have to check the speed rating of the tires on my trailer. (The Michelin's on my truck are not rated to go over 85).



The people on this site make it very enjoyable to own CTD's.

 

[GLASMITHS]

Low rpm towing ?

If you will look in Jeff's sig you will see that BD puts a pressure lock on the transmission, which increases the fluid flow/pressure at light throttle. A stock transmission does not have this, and you will kill your transmission fast if you do it very much. My transmission vendor says never under 1800 and by that my downshift point is 1900 unless I am gaining speed; but never cruising.



Mine lived for 73K pulling a 16. 5K 5er. A friend has 167K+ (that was 3 months ago) on a stock transmission. 36K GVW and he pulls it every day. 3rd gear at 65mph. So figure it up, Your ears or wallet.

 

[pwr2tow]

The rule of thumb is to watch RPM's no matter what the speed is when the transmission is in lockup. The RPM's should never drop below 1700 to keep the transmission happy. Remember the gradiant marks on the RPM gauge are in 125 RPM's markings, another great enginering thought from DC.



Ron

 

[CumminsPuller]

192,400 miles................

Well... ... ... . for 192,400 miles now I have been pulling a 40' gooseneck trailer weighing in at 8000lbs. Once loaded my entire rig can weigh anywhere between 15k and 35k lbs. Everything is stock (even the poor excuse chrysler calls a transmission) on the truck, but I have added an EZ at 87,000 miles with it set on the middle jumper setting. If I have nothing on the trailer I pull it in overdrive. But to get to OD whenever I am pulling my trailer unloaded this is the sequence I have followed religiously since day one. From a dead stop the truck is put in 2nd gear. I let the 1-2 shift happen on its own. Once I am in second I hang out there until just around 40mph (+/- a few MPH's). My foot comes off the gas, shift to drive (OD locked out), let the shift happen then slowly apply the pedal until TC lockup, once locked up I get on it a bit more. Once in 3rd I stay there until 65mph (2500-2600 RPM), foot comes off the go pedal, punch the OD button, let it shift, then slowly apply the pedal again ontil TC lockup. If I have the trailer loaded I never pullin OD. I just leave it locked out and cruise at 60-62mph. Just my $1. 00 worth. But I am anxious for it to go out..... I want one of those DTT Trannies... ... ... .



Jason

 

[cwsoules]

I tow in OD all the time. I have set my DTT Smart Box to retard the shift to OD to 57 mph. This ensures that the engine torque is high enough. I watch EGT and boost when it starts to get hilly so I can anticipate the increasing load so I can shift out of OD before it happens automatically. My 5er when loaded is about 10,200#.

 

[PaulCreamer]

Quote: But I am anxious for it to go out..... I want one of those DTT Trannies... ... ... .

Wonder how hard it would be to convert an automatic over to a manual when that day comes?

 

[CumminsPuller]

PaulCreamer.........

That is a good point... ... ... I wonder what the cost difference between doing the DTT ($4500. 00) and a conversion to a standard with a South Bend Clutch... ... You've got me thinking now... . Has anyone else done the conversion and acn get me in the ball park on the figures?



J

 

[Reddog1]

Do you really want to row your Ram everywhere you go?





What I see great about a stick :



1. The stick guys have absolutely no problems knowing when to shift (goes forward, must be in correct gear).



2. Stick transmissions never need work (their cheap).



3. Never need to replace the clutch (their cheap).



4. Never need maintenance on the clutch or transmission.



5. The necessity of having something to keep their right arm and left leg busy every time you stop, start or slow down below about 35 MPH.



6. Don't over crowd with three people in front (fill center of seat with a shift lever).







I guess I am just getting too old . I have rowed so many vehicles through the years I no longer see the glory.





LOL





Wayne

 

[Dean Upson]

Originally posted by Reddog1

Do you really want to row your Ram everywhere you go?

I guess I am just getting too old . I have rowed so many vehicles through the years I no longer see the glory.

I see your point Wayne, but that six speed sure is sweet to "row" . Don't know about any glory in shifting, it's mostly what you like and are the most comfortable with .



Dean

 

[bmoeller]

Originally posted by Fireman Dave

higher speeds = hotter trailer tires, so that's another issue to ponder. This summer I plan to tow under 65 mph (after loosing 2 tires on a trip last summer)

Sounds like the tires didn't have enough air press. in them to me.



I have only ever lost one tire to blowout, but it was a bad tire, not low press. that caused it. This was on an old car trailer.



On the semi, I have never had a tire failure. I keep a close eye on the press. I have had some flats, but they were from picking up screws, bolts, or ocassionally thorns from throny locust trees when hauling out of the field. .

 

[Fireman Dave]

b,



Nope, the pressure was right on the mark. They didn't blow out - the tread seperated on them. Fortunately, I caught it before they did blow out. I can't say that excessive speed was definitely the cause, but I may have taken them past their limit enough to have an affect.



If I'm not mistaken, every tire (car, truck, trailer, etc... ) has a speed rating for them as well as a weight rating. And you are correct, improper inflation will lead to failure as well. Too low of a pressure leads to excessive heat which leads to the failure.