05 F-350 6.0L Diesel downshifting problem?

Figgy · Oct 19, 2009

I just purchased an 05 6.0L powerstroke. I'm kind of new to the whole diesel thing, but correct me if i'm wrong. The whole point of a diesel motor is more power and better towing. Atleast that is why I bought one. I just got back from colorado and montana on a hunting trip and I was less than pleased with my truck. We were pulling a 24ft open snowmobile trailer with 3 four wheelers and the bed of the truck was plum full to the topper with bags and coolers. At most we had 7000lbs of stuff. My problem is that I couldn't even set the cruise with a tail wind and keep the truck from downshifting. That to me is unacceptable. For that I could have bought a gas motor and saved myself the extra 5 plus grand. I could understand if I was pulling 10,000lbs and had a 20 mph headwind, but that wasn't the case at all. Does anyone have a soution to this problem? Any help would be grateful. Thanks.

Squirrelchaser · Oct 19, 2009

Does the truck feel underpowered, run poor, have a cel on. What kind of fuel milage did you get. How many miles are on the truck. Do you have tires that are conciderably over stock size. You may want to have codes checked if the truck is feeling under powered. 6.0 were known for turbo problems in 04.5-0.5.

Transporter · Oct 19, 2009

Should have bought mine..See swapmeet...Also hows your air filter could be a long list of problems but was it just shifting down out of overdrive?

jthussey · Oct 19, 2009

When my 05 3/4 was stock, I pulled a 4-place with 4 sleds and gear in the truck out to Montana from NW MN and i could count on one hand how many times it shifted out of OD. That was @ 75 mph. How fast were you going? Sounds to me thats there's something wrong. If you were going 60 i could see it downshifting but if around 65 and up towards 75 it shouldn't be doing it.

blackcloud2k · Oct 19, 2009

turbo, plugged egr, clogged air filter, clogged fuel filter, turbo is a little weak...and the list continues with those 6 leakers. A great strong running truck when they are running right.

Coxy · Oct 19, 2009

Depends on everything everyone has asked you up above about things being wrong, tire size, etc, But if your running it stock it has lots of gears to chose from, id rather it shift and run in the zone then making heat and being out of where it wants to run. Again, thats baring any issues you have overlooked. I've pulled 8000 and 12000 pounds with my 05 6.0 on 37's, and even without a tow tune in it, pulled like a champ.

Norracks · Oct 20, 2009

I've had problem's with mine to, I have an 05 F-250 with the 6.0 L and especially in the summer towing the boat in the heat and pulling a pass it sounds like the tranny is over revving and slipping (winding out) and I hear a high pitched whistling sound and like a bell ringing but every time I take it in to the shop they say tranny is fine and it shows no codes but then they think something is wrong with the turbo for a day or so and then say that there's nothing wrong and tell me to bring it back if it does it again, and of course it does because they never do anything to fix it in the first place. I have had it programmed by the dealer for the oversize tires 35" and has not helped it only has 60K on the OD. anybody have any idea's ?

blackcloud2k · Oct 20, 2009

the wistling is normal on those 6 leakers. With that turbo the wistle like a freight train when loaded. do either of you have guages? What do your boost numbers, and egt numbers look like when this happens?

Figgy · Oct 20, 2009

I appreciate all the input. First off it is bone stock. Stock tires and everything. I have done a complete maintenance check on it when I purchased it and everything seemed fine. New fuel and tranny filters with new tranny fluid, brand new air filter the night before I left. Had a buddy check the computer on his snap on machine and no codes came up. Checked hoses on turbo. As far as power and boost, the truck seemed to have plenty of power and it ran good, it just downshifted. The one thing I did notice is once I got to cruising speed I would take it out of tow/haul mode and it seemed to let the motor work a little before it would downshift. I think that the tow/haul is to aggressive when trying to use cruise control. The second you would loose a mph it would downshift. The boost was between 10 and 20 lbs most of the time and when it would downshift it would crank up close to 30 lbs. As for speed and mileage, I thought it got ok mileage. I ran anywhere from 65 to 85 trying to find where the truck liked pulling a load and got anywhere from 10 to 14 mpg. The truck only has 40k miles. How do you know if your turbo is working like it is supposed to? Anyway to check it easily?

snowdog484 · Oct 20, 2009

A couple of years ago a wire to the turbo sensor broke and caused the truck to down shift on the I90 every time on a uphill pull. Could be that or the turbo sensor itself.

chamuza67 · Oct 20, 2009

05 ford 6.0

bought one new had same problem every little hump in the road it would kick down and i took it in and they could do nothing to fix it, said it was the nature of the beast so i sold it and got 06 duramax love it. I had couple ford diesels before that one and loved them but they were 7.3's they never could get my 6.0 to run right

jthussey · Oct 20, 2009

When i pull with my 05 6.0, and lugging the motor when i hit a good hill. thats when i see max boost and highest egts. if it can't hold speed it will then downshift and lower my egts along with the boost. You said that before you even see max boost its already downshifting? doesn't seem right to me.

I have to make my truck downshift on some occasions (even when ecu is stock) because the damn truck will pull like locamotive and just have the turbo barried @ 30 psi and my egts get up over 1100. In order for me to lower the egts is to smash the gas so it will downshift then feather the throttle so it doesn't upshift right away. The 6.0 will pull like crazy, something just doesn't seem right. Either that or i just got a lucky one.

Tec · Oct 20, 2009

I wired a torque converter lock switch on my dodge, really helped for towing! keeps the tranny from down shifting and unlocking the converter.

jthussey · Oct 20, 2009

Hey Figgy!

If your interested I have a hypertech power programmer III that would work on that truck. If you wanted to give it a try I will send it to you, you can try it out for a bit and if you like it I would get rid of it for $100. Its the coolest (egts) running programmer that i have tried. It has excellent power and with great driveability. The reason why i would get rid of it is because i now have a SCT by innovative that adjusts my tranny more than the hypertech and does give me a little more power. But along with that power is higher temps.

PM if interested and i can send you some pics of the module.

Blk88GT · Oct 21, 2009

I'd be careful running a programmer without head studs on the 6.0s.....

merlin2569 · Oct 21, 2009

If you are getting 10-14 towing at 65-85 mph i wouldn't worry about it too much. Not sure what kind of mileage you thought you were going to get with a stock diesel, but pulling with a gas at those speeds you would never get 10-14. This is just my opinion on this.

tgaug21 · Oct 21, 2009

I think it's pretty normal for the 6.0's to downshift pretty excessively... especially the 05+. In my 03 6.0 I almost have to put the pedal to the floor for it to downshift when pulling something heavy. As for something like an open place snowmobile trailer, I never use my tow haul because its just too annoying and shifts perfectly fine without it, and have never had a problem in doing so. My Dad has an 06 6.0 and for some reason it downshifts a ton compared to mine, seems like it does it more when using the CC

.
Also, I would count on doing egr delete, head studs, new injectors, and a fuel pressure spring. You will end up doing it at some point, and it makes a world of difference in how they run IMO. Just thought I would chime in my .02

blackcloud2k · Oct 21, 2009

that 5r100 allow having that extra gear it will down shift more than a 4r100. Its just that extra gear in there that gives the truck more room to play. Your boost numbers seem right now. I wouldn't worry about it. I know on my 7.3 with chip, turbo, injectors and all, it pulls way better with my 80hp daily driver program then it does in my 60hp tow program because it has just a little more power to keep it from having to downshift...but it will smoke out the interstate if I get it lugged down to much on the uphills and my tc lock switch is on.

Figgy · Oct 21, 2009

As I stated earlier, gas mileage wasn't an issue. I thought it did ok for mileage. It is what it is. Too many factors go into gas mileage to worry about it. I just thought I would be able to get in the truck set the cruise at 75 mph and the motor would pull it like it wasn't even there. Maybe that is just how they are. With the new tranny and that extra gear maybe that's how they are. I'm really not looking for a chip or a programmer or anything like that. I don't know a thing about diesel's and that opens up another can of worms. I want to keep it simple. I was told to try a shift enhancer by bully dog, but I can only find them for 7.3's not 6.0's. Maybe a torque converter lockout is the way to go. The tranny didn't seem to let the motor work at all before it would downshift. It would just downshift right away before the motor had a chance to lug. I thought that's what diesel where supposed to do, lug way more, not like a gas motor.

rdr99 · Oct 21, 2009

The 6.0 doesn't like to lug, it likes to rev. The SCT programmer is the way to go, nothing else.

05 F-350 6.0L Diesel downshifting problem?

Active member

Well-known member

New member

Well-known member

Well-known member

Well-known member

Well-known member

Westbound and down

Well-known member

Similar threads