I bought a 2003 F-250 Super Duty 4x4 last year, with a 6.8L v10 gas engine (4sp auto). Only has 78k on it, and is bulletproofed. It was obviosly taken very good care of. But when I bought it, I noticed the transmission shifted a little hard, but the dealer told me that was normal for a truck. I've never had a pickup, only a few Durangos, and I know the owners of the dealership so I trusted his manager's word. I tow a 37' travel trailer (~8k lbs), and sometimes the transmission seems to "slip" ( or bucks a little) in low RPMs of 4th gear, and sometimes when I try to accelerate from the low RPMs of 4th gear. It seems the issue is mostly (only) in 4th gear. I've taken it to 2 mechanics, and both have told me it's one of the highest end transmissions you can get, but would need to charge me about $250 just to get in and look at it. There are no metal filings in the trans fluid, and no burning smell of the fluid. Could this be a bad sensor?

FYI, AAMCO gave me a quote of $2500-3000 without even knowing what is wrong with my tranny. Will probably take it to a Ford dealership next, but I'd like to be more informed beforehand so I don't get taken advantage of.

Also, is it normal to only get about 6-7mpg when towning, and no more than 10mpg at most when not towing (even on hwy)? It's a real gas pig.

 

Welcome to the site..

The V10 is not shy about stopping regularly at fuel stations. Good platform, good power/torque but not good on MPG. At all...
78k on the 4R100 and it needed to be bullit proofed? Who’s trans?
Within an OE build the 4R trans are not known to shift hard or excessively firm. A trans upgrade/kitted, shifts generally are firmed up. Soft shifts tend to cause wear/heat when used in more severe applications.

At times, Ignition related (plugs/coils) can mimic a slip feel at throttle tip in and should be ruled out.
If a slip in OD, not in the other ranges, I’d consider a converter shudder, but most of the high end trans upgrades use a substantial converter over OE.
Trans has how many miles on it now? Serviced when? No OD light flashing?

If the trans was replaced fairly recently, it may have a limited warranty remaining. I’d check in with the builder/supplier if it proves out to be an internal slip condition..

 

Thanks for the response! Some of that is over my head, but I will address with a mechanic. Per some of your questions:

* 78k on the 4R100 and it needed to be bullit proofed? Not sure if it "needed" it. That's what I've been told by 2 mechanics. It also has a heavy duty K&N air filter (oiled). But I don't think it was used to tow very much, nor for offroad, as there was no brake controller, and the trailer connections looked like they were never used.
* Who’s trans? Don't know since I bought it used from a dealer and there isn't any paperwork.
* Trans has how many miles on it now? Serviced when? Same answer as above.
* No OD light flashing? No, though it seems to happen less with OD off. And of course I keep it off when towing.

Would the ignition problems show up on a computer reading? I'm thinking it may not have had a tune-up for a while, and will probably get that done asap.

Any chance it could be a bad fuel pump? The gas tank does have a bad seal and leaks when I fill it up. Not sure if it's a bad hose, seal, or the filter canister is clogged. Gonna cost me $250 for that as well, just to drop it and check it out.

It does have a bad diode in the alternator and I need to replace it, as it runs my battery down if the truck sits for a few days without starting.

Thanks for your input!!