6R80 Transmission Question O/D

[Munchie]

2009 EB V8 4.6 3v with 6R80 tranny:

I've been having fuel mileage issues so been recording on the scan tool for a few trips and have addressed a few things (usual suspects) but it spawned a question about the tranny.

I happened to notice that when I am travelling at on the highway it cruises in 6th gear (1800 - 1900 rpm) and I turn off the O/D the scanner indicates it goes straight to 4th gear (not 5th) and about 3200 - 3300 rpm. Is this normal? I would have assumed it would have gone to 5th gear at about 2400 rpm with the O/D off.

If this is normal, than I assume that the 6R80 has 2 O/D gears not 1 like my old 5 speed and when I turn off O/D it turns off both 5 and 6?

Thanks for any info/help you can provide.

 

[07EddyB]

I was surprised by this as well - I'm not familiar with the internal workings of the transmission but this fact has been pointed out multiple times on this forum and it has been my experience as well. The 6R80 does indeed drop two gears. It's a common complaint from people that want to tow with overdrive off. I guess that 5 and 6 are so close that they couldn't just drop one gear.

 

[Munchie]

Thanks for the response. I've been reading a couple of other threads over the last couple of hours now and I have seen this come up. It is very unfortunate as my father has a 2017 F150 with the 6R80 and his setup turns off just 6th gear. It's not really an issue towing the boat as I can tow the boat with O/D on and it doesn't hunt. However, I bought a new enclosed snowmobile trailer and although it weighs a 1/2 of my boat with the snowmobile and gear in it, the extra wind resistance causes the tranny to hunt so I have to drive with O/D off. Gas mileage is terrible @ 3200 rpm with a parachute behind you . Between that and the tiny tank I'll be lucky to get to the lake and back (150 miles round trip).

 

[07EddyB]

I assume you live in a hilly area - because that engine and trans combo should handle that just fine.

You mentioned that you were having fuel mileage issues. That's a red flag for me - you have something else going on.

 

[Munchie]

Nearly flat as a pancake out here. No doubt something is up with mileage though. I am about 15% - 20% off right now in my opinion but tracking the issue isn't easy as there are no other obvious symptoms. Idle is smooth as silk, shifts are too, no hesitation, MOD$06 data shows no misfires, LTFT is only 8% and short term varies +/- 2%, fuel rail pressure is spot on, I can see on the scanner I am in closed loop and I tested the PCV valve and it's functioning fine (speaking of which why did they put it inside the valve cover on this model?). Open to any thoughts as to what else to look for.

I've cleaned the MAF but haven't had a chance to take it out for a rip since. When I do, I'll pull a set of readings to check VE. I'll put the vacuum gauge on it on Monday to see if their is a restriction. I am doing the plugs and fuel filter that evening anyways as part of reg maintenance (90k for the plugs).

As for towing the snowmobile trailer, it is basically towing a sheet of plywood that's 6' x 8.5' face on. For those that tow similar sized trailers such as hard side campers whats your mileage? What gear and RPM are you towing at 60 - 65mph?

Update: I took it out for a trip to the lumber store. On the way there I made some WOT runs from a stop to calculate my VE, and it is spot on between 95% and 98% on three separate runs. This result indicates that my old school vacuum assessment isn't going to show any issues (restrictions) but I will still slap the old meter on it to double check.

 

[thebrakeman]

Expressway (60-70mph) driving with our 5200 lb travel trailer gets 8mpg.
2-lane highway trips (50-60mph), I get 9-10mpg.
And yes, I'm a big complainer around here about locking out 5th and 6th.
If I push the speed past 70mph, it puts the engine into a higher torque area, and it will sometimes hold 6th with the TC locked up. Tucking in behind a semi helps, too. But you're not supposed to be taking ST trailer tires past 65mph. In the end, I try to leave OD on, and let it find a gear. But if a lot of hills, or wind, and it's hunting, I'll shut off OD.

 

[Munchie]

Thank you. I figured that's what you should be getting and adds evidence that I was 15 - 20% off on gas mileage. I was concerned that my tranny was acting up with the drop 2 gear issue but it's supposed to do that . Back to checking the little things. Most of the maintenance work is done and plugs went in on Monday. I'll be able to get some real world info on mileage over the next while. I will get some highway miles tonight to the landfill and then out to the cabin next week so we'll see.

To give people a reference, I am of the opinion that my mileage went from (these are averages at about 60 - 65 mph):

- 20 mpg to 18.5 mpg highway with nothing behind the truck
- 15.5 mpg to 14.25 mpg highway with the boat
- 13 mpg to 11.75 mpg highway with the flat deck (but wind catching ramps) tractor hauler
- Haven't had enough experience with the enclosed snowmobile trailer to give a comparison but I did get 7.3 mpg

 

[Christobal65]

Honestly I'd say both the before and after mpg is still within the 'normal' range. I only ever see above 16 on all highway with speeds below 70mph. Towing a 15+ft open cargo trailer drops me down to 12ish.

Here's pretty much all the miles ang gas I've put through mine in the 2 years I've owned it. 07 V8 Explorer (Ford Explorer) | Fuelly

 

[Dag06XLT]

I pull a 2-place clam shell style enclosed snowmobile trailer with two sleds and get a consistent 11-12 mpg on the highway and leave it in D w/OD at 70 mph and let the trans decide what to do. Usually about 2K rpm when OD kicks in. I'm rather flat going through Wisconsin. It only down shifts on some large hills. With the V8, it shifts much less than my previous '06 4.0. With a 7300# tow capacity, my 1500# should be a breeze on the trans even with OD and cruise. I'm tired enough from riding trails 100's of miles, my legs need a break for the 7 hour drive home with cruise.

 

[Munchie]

Thanks guys. In limited use I've seen an improvement back to the higher end of where I think it should be. Again, appears to be just regular maintenance items that have brought things up. If each thing only helps by a % or two then it can add up. In case your wondering:
- MAF sensor cleaned (10 minutes)
- cleaned the throttle body including IAC (2 or 3 hours)
- run a couple bottles of seafoam through gas tank (how long does it take to pour it in?)
- changed plugs (70 minutes)
- I have decided to wait to change the fuel filter until this last bottle of seafoam is ran through

 

[Munchie]

Hello - I know how often people search for information to find a problem similar to theirs in a thread but then find it without resolution posted or updates at the end so I thought I would provide an update regarding the poor mileage.

I still haven't done the fuel filter but I have put a few miles on the truck towing the boat and I do believe (knock on wood) that I am smack back where things should be with respect to mileage.

This latest trip I traveled 300 miles round trip to NW Ontario for a week at the cabin with the family. Towing the boat fully loaded, 4 people in the EX and all stuff that goes with them I averaged 15.63 MPG on the trip at 65 mph for most of it. 100 miles of that I was bucking a good headwind and there was some hilly twisty driving thrown in to the mix too.

Edit: should of mentioned that the AC was on for the majority of the trip as well.