Towing in overdrive

[Builder]

2200 IS too fast for that diesel. It doesn't want to run long periods of time there. One thing worth mentioning is that the ZF-5 wasn't a ZF-6 with one gear missing. It's not as good of a transmission.

Good idea on the pyro on your truck. Just put the pyro sender right in the exhaust manifold. You're actually safer than a turboed truck because if the tip should break off, there's no turbo downstream to destroy.

You might find that you'll run higher EGT in O/D than 4th, but you can run a diesel all day at 11-1200* with no damage. That's what they were built for. If it were me, I wouldn't bother with a turbo on a truck that old. You'd be better off just buying a turbocharged truck. Just run what ya brung-cheaper in the long run.

 

[Big Bri]

2200 IS too fast for that diesel. It doesn't want to run long periods of time there. One thing worth mentioning is that the ZF-5 wasn't a ZF-6 with one gear missing. It's not as good of a transmission.

Good idea on the pyro on your truck. Just put the pyro sender right in the exhaust manifold. You're actually safer than a turboed truck because if the tip should break off, there's no turbo downstream to destroy.

You might find that you'll run higher EGT in O/D than 4th, but you can run a diesel all day at 11-1200* with no damage. That's what they were built for. If it were me, I wouldn't bother with a turbo on a truck that old. You'd be better off just buying a turbocharged truck. Just run what ya brung-cheaper in the long run.

If i can ask you say that 2200 rpm is a lot for his truck, which i think is an 88 model. I own a 96 with the 7.3 turbo 5 speed, when i'm in 5th gear i'm turning 2600 to 2700 rpm at 70 mph and i do that all day even when pulling a trailer. I never liked the fact that i turn so many rpm's but what else can i do.
i don't want to be "that guy" going down the interstate at 45mph

as of today i have just over 200k on the truck (i put 120k on it) and have not had any trouble. so is it ok to run the turbo trucks at that rpm? or should i be looking for a new truck?

 

[RobertN]

Out of curiosity, what gears do you have?

My Dodge has 4.10's. 70mph is more like 2100rpm. I wouldn't mind swapping to 3.73 some day.

Unless you have 4.88's or even lower, those rpm sound really really high.

If i can ask you say that 2200 rpm is a lot for his truck, which i think is an 88 model. I own a 96 with the 7.3 turbo 5 speed, when i'm in 5th gear i'm turning 2600 to 2700 rpm at 70 mph and i do that all day even when pulling a trailer. I never liked the fact that i turn so many rpm's but what else can i do.

 

[jayste]

FF, in my '99 F250 w/ 7.3PSD and ZF6 using OD I get around 12mph when pulling a good load (4 horse gooseneck) so I'd think you're about right. I've used mine for hauling for probalby 1/2 of it's 250,000 miles and used OD everytime I pulled the trailer when conditions called for OD. But, like Builder said, we might be compairing apples to oranges due to different engines and trannys.

RobertN, mine will run 2000 rpm at 70 mph with 3.73 rears.

Jay

 

[Diamondpilot]

Gears are one thing but tire size throws it all out the door. Ford likes big tires and wheels compared to GM and Dodge so comparing just gears is pointless. Tire size can make a 4.10 in one truck run like a 3.73 in another.

Chris

 

[Big Bri]

Out of curiosity, what gears do you have?

My Dodge has 4.10's. 70mph is more like 2100rpm. I wouldn't mind swapping to 3.73 some day.

Unless you have 4.88's or even lower, those rpm sound really really high.

i do have 4.10 gears, i don't think my 5th gear is an overdrive. . . it only drops about 400 to 500 rpm going from 4 to 5th. it also doesn't say any thing about over drive on the shifter, and i don't remember anything listed in my book about what the 5th gear ratio is.

 

[RobertN]

Good point. Running 4.11's with 33x12.50's and swapping to 35x12.50's would be like swapping to 3.73's.

Gears are one thing but tire size throws it all out the door. Ford likes big tires and wheels compared to GM and Dodge so comparing just gears is pointless. Tire size can make a 4.10 in one truck run like a 3.73 in another.

Chris

 

[FlaDon]

I tried running it in 4th gear but gave up after 10 miles. It's just easier running in overdrive, it seems like running it at 2200 rpm is to fast for the motor, and the water temp was going up, it was about half way up the scale when I started using overdrive and after that everything worked just fine. There was only a couple of bigger hills that I had to use 4th for. I think that being the torque curve being at 1400 has a lot to do with it. Next thing I'm going to install will be a pyro so I know how hot I'm actually running. I was thinking of putting a turbo in this truck, but I'm hesitant because I don't want to cause more unforeseen problems.

The torque curve is what gets a lot of the Diesels out on the highway as compared to the BBC and BBFs. With the torque max coming in at 1600/1800 and max HP at 2500/3200 rpm, a stock Diesel runs out of power at highway speeds of 65 MPH on grades and 4.10 gears. Meanwhile the 8.1's torque peaks at 3200 and the HP at 4500 RPM. 4.10 gears and stock size tires equals 3200 RPM unlocked torque converter in 4th in a Chevy 2001 DM/8.1/Ally at 65 MPH. 3rd = 4000 RPM which is past Peak HP on the DM or other Diesels. Keeping your truck in 5th helped push it into a better torque range for the speed. And ran cooler.

 

[Builder]

The torque curve is what gets a lot of the Diesels out on the highway as compared to the BBC and BBFs. With the torque max coming in at 1600/1800 and max HP at 2500/3200 rpm, a stock Diesel runs out of power at highway speeds of 65 MPH on grades and 4.10 gears. Meanwhile the 8.1's torque peaks at 3200 and the HP at 4500 RPM. 4.10 gears and stock size tires equals 3200 RPM unlocked torque converter in 4th in a Chevy 2001 DM/8.1/Ally at 65 MPH. 3rd = 4000 RPM which is past Peak HP on the DM or other Diesels. Keeping your truck in 5th helped push it into a better torque range for the speed. And ran cooler.

And that's why it's foolish to order anything over 3.73's with today's diesels. In fact, 3.55's would be more than adequate with a 650-700 ft lb diesel pickup making peak torque at 1400-1800 RPM. The less revolutions of the engine keeps it in its' max torque band. It economizes on fuel, too. I laugh at guys that get 4.10's with newer diesel trucks. Why do that? You're just wasting fuel and assuring your truck will be revved past its' sweet spot in many driving situations.

These guys with 4.10's, 4.30's & 4.88's behind a 650-700 ftlb diesel are actually running their trucks way past their sweet spot because they're over-revving their trucks down the highway. Sure, it helps launch the trailer, but who has ever run out of power towing a 12-16K trailer with a newer diesel? I never did, even with my stock 235/520 7.3L Powerjokes.

The other thing the numerically high gears hurt is boost. When the RPM's are way up, boost is lower because you can't "load" the motor. Diesels want to run down low in the RPM range, not lugging, but run low to make power & save fuel.

My 4800 has 5.38's and make ~18lbs boost max. I know several other guys running same trucks even with 4.10's making 25lbs boost. Sure, they can't launch like me, but they can pull a backhoe OK and once they're up to speed, they run lower RPM and waste less fuel. Their truck engine are more settled and mines revving anywhere past 45MPH. Only thing that helped me was installing an ES066-7B overdrive transmission to drop the RPM!

 

[RobertN]

So which is better, behind my motor? My '01 Dodge is stock, with an auto, and 4:10. 3.55 was standard, 4.11 was option; I was used to 4.11 behind a 351 in a 89 Ford F250. I guess this truck is not all stock, it does have a 4" exhaust and a BHAF.

So if I save my nickles and dimes for a ring/pinion swap, would it be 3.55 or 3.73? 3.73 would be right in the middle.

With 4.11's, it is a big change from OD to 3rd, especially on the freeway. At that point, anything over 50mph is really revving.

I run empty most, but tow my Kubota(4200 loaded with trailer), or a 7000lb mid sized 5th wheel.

I gave up a lot getting the 4.11's. Best UI have ever got is 19mpg empty, running Sacramento to Tillamook Or for a Scout camp. I babied it to get that.

I have never researched it. I wonder if I could swap gears without changing the carrier? Have done it on Jeeps; when I went from 3.73 to 4.88, it required new posi's; ring gear was much larger. Back then, I think it was about $250 labor per axle, $250 for gears.

And that's why it's foolish to order anything over 3.73's with today's diesels. In fact, 3.55's would be more than adequate with a 650-700 ft lb diesel pickup making peak torque at 1400-1800 RPM. The less revolutions of the engine keeps it in its' max torque band. It economizes on fuel, too. I laugh at guys that get 4.10's with newer diesel trucks. Why do that? You're just wasting fuel and assuring your truck will be revved past its' sweet spot in many driving situations.