6.9 slow pulling hills

[Clayton]

I recently acquired a 1985 f350 2wd dually 4 speed flatbed with 3.55 gears. The truck runs great starts instantly, Although it has trouble maintaining speed on hills without having to grab third and wind the **** out of it. Things I have done are, Remove the restricter from the air cleaner, Bump the timing a hair, and uncork the exhaust. All of which helped some but not much. It has fairly new filters and doesn't smoke abnormally, Just a slight black haze when pulling hills. This is my first idi so this may be normal as far as I know, Just seems though it shouldn't struggle so much. Kinda makes me wish ida kept my gasser.

 

[dakotajeep]

Thats about right for a naturally aspriated 6.9 diesel. Your best bet for power is to run a turbo. It is the best thing to do to these trucks. Mine was worth EVERY penny!!!!

Mine would lag on hills. I would only be able to run 40-45 mph over the larger hills. It sucked!! My wife was along during one trip and gave me the permission to get a turbo......best investment into this truck!

Thad

 

[kas83]

I recently acquired a 1985 f350 2wd dually 4 speed flatbed with 3.55 gears. The truck runs great starts instantly, Although it has trouble maintaining speed on hills without having to grab third and wind the **** out of it. Things I have done are, Remove the restricter from the air cleaner, Bump the timing a hair, and uncork the exhaust. All of which helped some but not much. It has fairly new filters and doesn't smoke abnormally, Just a slight black haze when pulling hills. This is my first idi so this may be normal as far as I know, Just seems though it shouldn't struggle so much. Kinda makes me wish ida kept my gasser.

What kind of load, and what kinds of hils are we talking about here?

I've run naturally aspirated IDI's up to the Eisenhower Tunnel on I70 in Colorado, both empty, and pulling a 9,000 lb travel trailer. Empty, my uncles 7.3 with 4.10s and a 5 speed, would require a downshift to 4th to keep from lugging it and smoking like crazy at 55-60 mph. With the trailer, it was about 20 mph, 27-2800 rpm in 2nd gear, to keep going. Running right with the semi's is about as fair a comparison as far as speed. At this rate and pace, the truck was still getting better mpg loaded and pulling the mountains, than the 460 powered truck it replaced, got empty. They're not going to haul ass when they don't have a turbo, but they get the job done, and do it reasonably economically.

 

[Clayton]

Thats about right for a naturally aspriated 6.9 diesel. Your best bet for power is to run a turbo. It is the best thing to do to these trucks. Mine was worth EVERY penny!!!!

Mine would lag on hills. I would only be able to run 40-45 mph over the larger hills. It sucked!! My wife was along during one trip and gave me the permission to get a turbo......best investment into this truck!

Thad

Thanks, I guess I'll just have to live with it if that's the case.

 

[Clayton]

What kind of load, and what kinds of hils are we talking about here?

I've run naturally aspirated IDI's up to the Eisenhower Tunnel on I70 in Colorado, both empty, and pulling a 9,000 lb travel trailer. Empty, my uncles 7.3 with 4.10s and a 5 speed, would require a downshift to 4th to keep from lugging it and smoking like crazy at 55-60 mph. With the trailer, it was about 20 mph, 27-2800 rpm in 2nd gear, to keep going. Running right with the semi's is about as fair a comparison as far as speed. At this rate and pace, the truck was still getting better mpg loaded and pulling the mountains, than the 460 powered truck it replaced, got empty. They're not going to haul ass when they don't have a turbo, but they get the job done, and do it reasonably economically.

No load, It's kinda hard to explain how steep the hills are.

 

[Black dawg]

in an unloaded n/a idi ive been passed by loaded semis. it was pretty funny, they were trying dims and brights trying to see through the fog coming out of our tailpipes.

 

[Clayton]

Yeah had I known It was so slow on hills I probably wouldn't have got it, It runs like a ***** ape on flat ground though.

 

[Andylad13]

Yeah had I known It was so slow on hills I probably wouldn't have got it, It runs like a ***** ape on flat ground though.

She definatly won't break any land speed barriers, but she'll get the cargo where it needs to go. Besides, more HP costs money to get, and to replace broken parts from! These engines give you a good amount of pulling power compared to the cost of newer ones that only get it there faster.

 

[timothyr1014]

I would place money on the 3.55's hurting you...on my 86 I have 4.10, and on my last run from phoenix to san diego going over the I-8 grade I pulled 65 with room to spare (truck and ~1800lbs in the bed)...the down side to 4.10 is with the 4-speed you are turning the motor at a decent clip and highway economy sucks

 

[SparkandFire]

I would place money on the 3.55's hurting you...on my 86 I have 4.10, and on my last run from phoenix to san diego going over the I-8 grade I pulled 65 with room to spare (truck and ~1800lbs in the bed)...the down side to 4.10 is with the 4-speed you are turning the motor at a decent clip and highway economy sucks

I agree with this, I just ran a bed full of firewood up a pretty decent hill and I was impressed by how well my truck did (even though a cummins smoked me) and I've got 4:10's also. I'm solving the highway economy issue this weekend with a dose of ZF5...

 

[69oiler]

i'll buck the trend and say i think something's up with your truck. if you are runnning empty you should be able to run in 4th gear (direct drive 1:1 ratio) up about any hill i've seen at 50+ mph. my old IDI 4 speed with 3.55 pulled hills just fine. i would downshift only when towing. even my '89 with C6 will run good up hills. neither had a Turbo.

you may have a weak injector pump, or maybe your timing's still not quite right. remember we are talking an EMPTY truck here right?

 

[dakotajeep]

69oiler

You may be right in that he may have some worn out parts that could help a little. But in the end these are still not fast trucks when going up hills. But we cant mislead the OP in thinking changing those parts is going to make it perform like it has a turbo!

That said these rigs are great for pulling and driving inexpensively!!!

Thad

 

[Agnem]

i'll buck the trend and say i think something's up with your truck. if you are runnning empty you should be able to run in 4th gear (direct drive 1:1 ratio) up about any hill i've seen at 50+ mph. my old IDI 4 speed with 3.55 pulled hills just fine. i would downshift only when towing. even my '89 with C6 will run good up hills. neither had a Turbo.

you may have a weak injector pump, or maybe your timing's still not quite right. remember we are talking an EMPTY truck here right?

X2. You "recently aquired" this truck because the person who had it before you hasn't probably spent any money on it in a while. How many miles are on it? It's likely the pump and injectors need to be replaced, or at a minimum you need to get the thing timed properly. Whoever times it should be able to tell you how much life is left in the pump. If it's worn, the fuel needs turned up to compensate. What are your EGT's? Your black smoke may be due to poor fuel atomization. Get the injectors pop tested. There are quite a few things you can/should do to ensure your running as best you can, rather than just guessing on the timing and hoping for the best.

 

[6 Nebraska IDIs]

Like others have said I think you have something up with your truck. It'd be worth timing it at the very least. When these motors wear out the injection pump the timing moves. Thus the need to re-time them periodically. But the one thing no one else mentioned and I myself have personally had experience with are locked front brake calipers. I'm completely serious. We drove my moms crew cab for atleast two years with bad front brake calipers on it. Took it in to have the front suspension serviced and they did the brakes at the same time, didn't catch the brake caliper problem. We thought the motor was worn out, it literally didn't want to pull itself. Let me tell you forcing these things to drag themselves around wears on everything. It is definitely worth your time to atleast check the brake calipers for excessive grab.

 

[Agnem]

Usually if they are stuck that bad, you will melt a hub.