poor fuel mileage on new to me truck

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dwall731

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Jun 19, 2015
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Bought a 2005 3500 4x4 crew cab about 2 months ago. It has 33x1250s and it is getting about 11 mpg. Ive always had fords and ended up getting a good deal on this truck so I traded the ford for it. I know very little history on the truck other than it has recently been rebuilt. I put a smarty touch on it to see if that would help any and it got me to about 12 mpgs. I really feel like the transmission or converter one is slipping. It has 3.73 gears but running gps verified 70mph I taching 2300. Is there any thing I can do to verify a problem a problem in the drivetrain or is there anything else I can try?
 
Those rpms seem high. I have 4.10 gears with 33's, auto, and only see a little over 2000 rpm at 70. Are you sure on the gearing? Im assuming 48re trans
 
Yep, had the rear diff cover off to change the oil a couple weeks ago, and the pinion had 11x41 stamped on it. And as far as I know it's an 48re.
 
Bad injector will do that. Won't know it till you melt a piston! Any smoke whitish on first start up?
 
You should be able to tell if the converter is locking up.


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No white smoke on start up, only after it has been idling a while(5 minutes or so) and I go to take off. But its only for a second. The truck had a 12000 mile warranty on the engine from the shop that rebuilt it, but they are not wanting to work on it. It has a front seal leaking so I am hoping that I can get them to check it over while it is in there. They dont have much experience with diesels that I can tell, but I didn't pick the place to do the rebuild, that was the guy that sold the truck.
 
Also every once in a while, while going down the road, the dash will ding at me and the wait to start light is on. Any ideas on that?
 
Did they use the old injectors or put new ones? Pull injectors have them tested take a look at the pistons with a boroscope! clean all your battery connections bad grounds do weird things!
 
Probably a dumb question, but I am assuming the injectors will have to go to a bosch dealer to be tested? I do know they replaced some injectors just not sure how many or how they determined how they needed to be replaced. Going back to the shop on Monday, using some oil, a gallon in about 3000 miles. Something cant be right somewhere
 
That's a lot of oil wonder if you ever seated the rings? Have you run it hard with a good load yet? Check for blow by and leaking underneath!
 
sounds like it has a few problems... and probably a ****ty mechanic in its past.

if my truck ever got 11 empty and used a gallon of oil i sure as hell wouldn't be driving it... something is NO BUENO.

i would be testing those sticks and doing a compression test for starters.
 
getting the truck back from the shop in the morning. Said other than the front seal leak they couldnt find anything wrong with the motor. They did check the transmission and TC and said the TC is shot and needs to be changed soon. Thinking about taking it to another shop and getting a second opinion on the engine. Think its worth it? Or should i get a new TC first as I am sure something in the drivetrain is slipping? Just ready for this thing to be right LOL My last truck was a 6.0 that didnt leak this much LOL
 
Did it "use" that gallon of oil or did it leak out the front seal? My old 03' would use 1-2 quarts of oil in between oil changes of 5,000 miles. Some of which leaked out the valve cover gasket and rear main, but on long trips it wouldn't use any. It had ~170k miles on it when I sold it.
 
I guess I am hoping it leaked out the front seal, just seems like a lot of oil for no more time than it leaked and no more than I drove it at the time.
 
Well I have ordered a DPC triple disc converter for it. Hopefully I can get it in and installed in the next week or so and maybe that will have all my issues fixed. is it worth it to put a valve body in it?
 
Got a DPC triple disc installed this week. Truck runs fantastic now. 75 mph is a shade above 2000rpm. I am curious though, as i was turning the flexplate with a screw driver from the inspection plate to remove and reinstall the TC bolts, it never really got tight like it was building compression. Seems like it should have gotten tough in a few spots.
 
Just turning it a little at a time with a screwdriver like that, you probably wouldn't feel the compression stroke. If your original converter was bad, that could explain your poor fuel economy if it wasn't going into lockup.
 
do you have a mini earth quake when you turn the engine off? Thats a pretty decent indication of compression, i would assume. but just get a 15mm socket and put it on the dampner and turn it over and you will feel and hear the compression.
 
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