Official word on overdrive and towing....

No amount of google whacking turned up a digital copy of the owners manual, so I gotta ask: What does the owners manual say about towing and overdrive ? For heavier loads it's overdrive off (sorta like tow/haul mode on newer trucks) but is there a weight above which it is required ? Been pulling ~3500 lbs around town with overdrive and it didn't hunt or anything. It's a 2500 gas with 4.10s which is rated at 8400 lbs towing.

Thx !

First, never use google. G is the enemy of patriot Americans and hell-bent to destroy this nation. Do not give them service. Delete everything Google that you can. Use an alternative search engine.

I don't think Dodge gives an official word on towing, just max numbers. These trucks are commonly over-loaded and worked hard all the time. This does not extend the life expectancy, but in the short term they are champs.

Generally OD is bad. OD is a gear described where the drive shaft will spin faster than the engine. This puts tremendous stress on the trans, and towing in OD will add even more stress. OD will create a lot more heat in the trans.
If you have a manual shift, I dont think your '14 is, then the 5th gear is an OD gear (and 4th is not really even a gear as it by-passes the trans gears and just passes the shaft rotation straight through where the engine and drive shaft turn in sync).

If you tow heavy it is tremendously important to have a trans temp gauge and drive according to the temp. Keep in mind that trans temp will lag a little behind what the actual stresses are on the trans as it takes time to heat up all that fluid.
180 degrees is getting hot, over 200 is really hot and I think 220 starts to burn the oil. When I run exclusively in 4th I can keep the trans temps way down, usually not more than 40 deg above outside temps. The engine will eventually heat up the trans some on multi-hour long drives.
As you get familiar with the temp gauge you will learn more.

The lower you can keep trans temps means the longer your trans will last.
Heat is coming from stress, and stress is bad on trans.

Use OD downhill (even 1 or 2% downhill) or with a tailwind, otherwise tow w OD off. You will want to keep speeds lower, maybe 65, to further save stress on trans. Air resistance, made more with trailer, is #1 friction factor to overcome and increases exponentially with speed increases.

Stock truck, anything more than a quad trailer or lawnmower, turn it off.

Now my truck for example, i hauled 3500lbs or so an hour with overdrive on. HOWEVER, i have a heavily built trans with billet converter and you KNOW when lockup is engaged. That and with the differential gearing and temp gauge and other modifications, i wasnt worried. 65mph on the interstate, never downshifted, stayed in lockup, temp stayed normal. Hell it even still got the usual 13mpg average. I turned it on once i was up to speed and settled in for the drive though. If you need to be changing speeds i would leave it off

Hmmm, I thought the trans - especially an 8spd - would get to 190-200 without towing. But then I have the 5spd so I'm not an expert. Also, don't the 8spds have more that one OD gear?

It also depends on the terrain - I hauled a 94 Accord back and forth from SC to FL, so lots of flat land. Used T/H and for a while kept it to 4th gear. But after a while, I tried it with 5th, and the trans temp didn't go up more than a degree or two. Accord weighs maybe 2500lbs.

Was going to haul my brother's 98 Dodge up to Concord NC, but U-Haul says our trucks are "too long" and they won't rent us a tow dolly or trailer. Weird.

These old 4spds dont like going over 180 degrees if you can help it. Shortens fluid life to like 20k if you consistently run it that warm. About 140-160 is ideal

I seem to recall that about the 2nd gens, isn't the OD an add on on the end of the trans?

Wahrsuul said:

I seem to recall that about the 2nd gens, isn't the OD an add on on the end of the trans?

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Yep

My truck runs cooler with the OD engaged than with it off.

In OD the transmission is "locked". The internals spin but the sprag is disengaged. Only the clutches on the OD and convertor are used. When the OD is off the internals push the fluid through the cooler at a higher flow and it doesn't cool as quickly.

Yes, I run a gauge, that's how I know.

Okiespaniel said:

My truck runs cooler with the OD engaged than with it off.

In OD the transmission is "locked". The internals spin but the sprag is disengaged. Only the clutches on the OD and convertor are used. When the OD is off the internals push the fluid through the cooler at a higher flow and it doesn't cool as quickly.

Yes, I run a gauge, that's how I know.

Click to expand...

The big reason for the cooler temps is fluid flow through the converter lessens with each higher gear. In OD the converter locks and quits using the fluid to multiply tq and instead it just flows through it and to the cooler

That's also why when temps get too hot it knocks you down to 3rd. 3rd can lock the converter as well and fluid flow is higher which spreads the heat input over a greater volume. Cools it better with the greater flow because of the surface area

dapepper9 said:

The big reason for the cooler temps is fluid flow through the converter lessens with each higher gear. In OD the converter locks and quits using the fluid to multiply tq and instead it just flows through it and to the cooler

That's also why when temps get too hot it knocks you down to 3rd. 3rd can lock the converter as well and fluid flow is higher which spreads the heat input over a greater volume. Cools it better with the greater flow because of the surface area

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Yes, but my transmission runs about 10+ degrees cooler in OD around town than in 3rd gear. It comes up a bit on the highway, because even in lockup the fluid is moving quicker with the 4:10s.

Also...when you get kicked out of OD because of fluid temps you've already started burning off clutch facings. The slippage is what's causing the heat.
What I'm saying is the self protection downshift doesn't work. The fluid is moving too quickly to expend it's heat.
You would be correct to add more surface area or more cool air across the what cooling surface you have to lower fluid temps.

I run OD all the time except when off roading in low range.

Mine acts the same way BUT i can tell you that when it kicks you down it DOES work pretty well to cool the fluid. Ran my truck for 4 years and 70k miles without lockup lol. Overdrive she got hot lol. I could watch it drop fluid temp 10 degrees on the gauge in less than 2 miles. That was before the PATC swap during high school

Mine does the opposite....drops about 10 degrees with od/lockup engaged. I was running down the I-40 in OD towing a overloaded 9x12 U-haul and truck full of stuff with the gauge at 100 degrees at 75. Then the OD blew when we got on the I-44 to Tulsa...

Perhaps a larger or different cooler design would help. I've considered swapping in a B&M cross flow for the Hays/Valley style.

I think lockup has more to do with that because the converter isn't adding the heat like it would unlocked. I had zero lockup whether i was in OD or not and in OD that built a lot of heat.

With my current setup though i might get to 140 at 75mph on a 95 degree day and that's with an inefficient bar+plate cooler lol. A good sized tube and fin doesn't even register on the gauge which goes down to 100

Okiespaniel said:

In OD the transmission is "locked". The internals spin but the sprag is disengaged. Only the clutches on the OD and convertor are used. When the OD is off the internals push the fluid through the cooler at a higher flow and it doesn't cool as quickly.

Yes, I run a gauge, that's how I know.

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NOPE . . . In O/D the O/D planetary gears are being used and generate heat. The issue with the early O/D transmissions that failed were because the lube holes in the intermediate shaft were too small and provided insufficient fluid flow to the O/D planetary - using the O/D in loaded/towing situations overheated the gears, which overheated the fluid and cooked the trans. Also, ATF +3 was the spec fluid at the time, which is crude oil based and had relatively poor temp resistance qualities. Informed trans shops would drill out the OEM intermediate shafts lube holes until the factory corrected the problem with larger lube holes and started to spec ATF +4, which is synthetic based and much more temp resistant. I think it was Sonnax that also sold the improved intermediate shafts.

In any case - while in L/U - O/D, while even though the converter is locked, the forward and direct clutches are locked, and it is a straight thru shot from the flex plate to the intermediate shaft - there can still be considerable heat generated by the O/D planetary gearset.

Okiespaniel said:

In OD the transmission is "locked". The internals spin but the sprag is disengaged. Only the clutches on the OD and convertor are used. When the OD is off the internals push the fluid through the cooler at a higher flow and it doesn't cool as quickly.

Yes, I run a gauge, that's how I know.

Click to expand...

Without a gauge I put approx. a 1000 limit on a trailer, towing in O/D.

EvilSpirit said:

NOPE . . . In O/D the O/D planetary gears are being used and generate heat. The issue with the early O/D transmissions that failed were because the lube holes in the intermediate shaft were too small and provided insufficient fluid flow to the O/D planetary - using the O/D in loaded/towing situations overheated the gears, which overheated the fluid and cooked the trans. Also, ATF +3 was the spec fluid at the time, which is crude oil based and had relatively poor temp resistance qualities. Informed trans shops would drill out the OEM intermediate shafts lube holes until the factory corrected the problem with larger lube holes and started to spec ATF +4, which is synthetic based and much more temp resistant. I think it was Sonnax that also sold the improved intermediate shafts.

In any case - while in L/U - O/D, while even though the converter is locked, the forward and direct clutches are locked, and it is a straight thru shot from the flex plate to the intermediate shaft - there can still be considerable heat generated by the O/D planetary gearset.

Click to expand...

Tomato/Tomatoe. I have to explain things to people I deal with in a simple as possible way. If I tell them under LU the main internals free wheel while the OD/TQ is locked/engaged and moving the vehicle they get it. The more I add, the quicker they glaze over.

Although I'm aware that a lot of shops redrilled the intermediate shafts because burnt clutches caused by lack of lubrication were killing the OD unit, that certainly doesn't explain my reality.

My gauge showed about 120 degrees before the OD failed. When the OD failed the temp shot right up to 210. I had to turn off the OD. That brought the temp down to a manageable level and I limped the truck 115 miles into Tulsa from OKC. My OD clutches were toast...pass the strawberry jam.

There are many people that pull loads far larger than a thousand lbs, in OD and run for years without failure.

It makes sense that the trans could cool down with the O/D shut off - at that point everything is just spinning 1:1. There is a small amount of friction through the bushings, the converter is locked, and there is a little heat generated by the front pump making pressure.

As to my "1000 lb rule" - self imposed from initial experiences with early/mid 90's Dakota's and Rams. I agree that the later versions with the updated OEM parts and ATF are much more durable than the RH units, but I'd much rather err on the conservative side, especially if I'm giving advice. I have probably towed my golf cart on a utility trailer 15-20k miles at freeway speeds in O/D with my 99 Dakota with it's 3.9/RE42/3.55 drivetrain and never had an issue, but I had a temp gauge and it never got over 180. Probably about 1400 lbs, and utility trailers pull "heavy" because of the expanded metal ramp acting like a 'chute.

And while I'm in "disclosure" mode. Since my friends (a 6 bay trans shop in the 90's) did testing on the RH/RE series transmissions in the 90's we have usually added a qt of 10w-30 synthetic oil at rebuilds and full fluid changes. It provides added lubrication, and has never created a clutch lining or wear issue - actually the opposite. Some of the early trans shop repair bulletins actually suggested this. While I know there are some auto transmissions that are very critical of the fluid used and friction modifier additive packages, the RH/RE series work just fine adding the engine oil. Some people may claim this is a bad practice, and really, I don't care - it has served us well.

EvilSpirit said:

NOPE . . . In O/D the O/D planetary gears are being used and generate heat. The issue with the early O/D transmissions that failed were because the lube holes in the intermediate shaft were too small and provided insufficient fluid flow to the O/D planetary - using the O/D in loaded/towing situations overheated the gears, which overheated the fluid and cooked the trans. Also, ATF +3 was the spec fluid at the time, which is crude oil based and had relatively poor temp resistance qualities. Informed trans shops would drill out the OEM intermediate shafts lube holes until the factory corrected the problem with larger lube holes and started to spec ATF +4, which is synthetic based and much more temp resistant. I think it was Sonnax that also sold the improved intermediate shafts.

In any case - while in L/U - O/D, while even though the converter is locked, the forward and direct clutches are locked, and it is a straight thru shot from the flex plate to the intermediate shaft - there can still be considerable heat generated by the O/D planetary gearset.

Click to expand...

Thanks for this excellent info! Now for some new-to-Rams questions, If you don't mind!

What constitutes "early O/D transmissions" - mainly, do I have one? 99 2500 petrol but I think with a bunch of non-stock parts - the axles in particular, check my other posts for more info. The truck has the tow package (trans cooler, Odyssey controller, factory hitch/wiring, etc).

I'm going to be doing a bunch of towing. A boat from sea level up over 5000 feet and back down to Tahoe, as well as a 6500 pound trailer from the high desert (4000 feet) to Tahoe at 5000 feet and then back down. Then another run with the 6500 pound trailer and lots of cargo weight, from the high desert along 447 into Black Rock with likely very high ambient temps, 110 or so. Elevation changes are just up and down desert highway hills, it's all pretty much at 4000 feet.

I'm planning to drain and replace the trans fluid before all that, next week. What's the best spec fluid to use, knowing what you know? Hell, I'll take advice on the best brand/spec engine oil, and all the other fluids/filters at that, since I'm changing all of them next week.

I'll probably stick a trans temp gauge in there as well. Anything else you can recommend or advise? With my last tow vehicles (F250 Super Duty 7.3 diesel and Sprinter 5-cylinder diesel) I ran with OD off unless I was going downhill or otherwise wasn't putting much of any load at all on the engine. On the Sprinter I had a Scan-Gauge so I could actually watch the LOD value in real time.

Thanks in advance!

I call "early" the RH units made before 1996 - by then they had the O/D cooling issue figured out.

As to fluids - name brand ATF +4 is the preferred fluid - it is synthetic based and has higher temp ratings than ATF +3. I also add a qt of synthetic 10-30 for added wear protection. Since I rarely tow much more than a golf cart anymore I don't really stay current with tuners to make an informed recommendation there.

Trans temp gauge is always a good investment. And although pricey, the cast aluminum deep pans are nice additions, too.

Oversized aftermarket trans cooler if you work your truck hard?